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sonar _dr hatemelbitar00201005684344.pdf

#دكتور_حاتم_البيطار #دحاتم_البيطار #timodentist Dr Hatem ElBitar د حاتم البيطار أستشاري وجراح أسنان زميل الزمالة المصرية محاضر ادارة المستشفيات ومكافحة العدوى 01005684344

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m.i.t
academy
‫االكاديمية‬
‫الدولية‬
Sonography course Basic and advanced
00201005684344
introduction
This course is an educational tool
designed to assist practitioners in
providing appropriate diagnostic
knowledge to care for patients.
The practice of medicine involves not
only the science, but also the art of
dealing with the prevention,
diagnosis,alleviation, and treatment of
disease.
The variety and complexity of
human conditions make it
impossible to always reach the
most appropriate diagnosis or to
predict with certainty a particular
response to treatment.
Therefore, it should be recognized
that adherence to these practice
parameters will not assure an
accurate diagnosis or a successful
outcome.
All that should be expected is
that the practitioner will
follow a reasonable course of
action based on current
knowledge, available
resources, and the needs of
the patient to deliver effective
The clinical aspects contained in specific
sections of this practice parameter
(Introduction, Classification of Fetal
Sonographic Examinations, Specifications
of the Examination, Equipment
Specifications, and Fetal Safety) were
revised collaboratively by the American
College of Radiology (ACR), the American
Institute of Ultrasound in Medicine
(AIUM), the American College of
Obstetricians and Gynecologists (ACOG),
and the Society of Radiologists in
Ultrasound (SRU).
Recommendations for
physician qualifications,
written request for the
examination, procedure
documentation, and quality
control vary among the
organizations and are
addressed by each separately.
This practice parameter has
been developed for use by
practitioners performing
obstetrical sonographic studies.

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sonar _dr hatemelbitar00201005684344.pdf

  • 2. introduction This course is an educational tool designed to assist practitioners in providing appropriate diagnostic knowledge to care for patients. The practice of medicine involves not only the science, but also the art of dealing with the prevention, diagnosis,alleviation, and treatment of disease.
  • 3. The variety and complexity of human conditions make it impossible to always reach the most appropriate diagnosis or to predict with certainty a particular response to treatment. Therefore, it should be recognized that adherence to these practice parameters will not assure an accurate diagnosis or a successful outcome.
  • 4. All that should be expected is that the practitioner will follow a reasonable course of action based on current knowledge, available resources, and the needs of the patient to deliver effective
  • 5. The clinical aspects contained in specific sections of this practice parameter (Introduction, Classification of Fetal Sonographic Examinations, Specifications of the Examination, Equipment Specifications, and Fetal Safety) were revised collaboratively by the American College of Radiology (ACR), the American Institute of Ultrasound in Medicine (AIUM), the American College of Obstetricians and Gynecologists (ACOG), and the Society of Radiologists in Ultrasound (SRU).
  • 6. Recommendations for physician qualifications, written request for the examination, procedure documentation, and quality control vary among the organizations and are addressed by each separately. This practice parameter has been developed for use by practitioners performing obstetrical sonographic studies.
  • 7. Fetal ultrasound should be performed only when there is a valid medical reason, and the lowest possible ultrasonic exposure settings should be used to gain the necessary diagnostic information .A limited examination may be performed in clinical emergencies or for a limited purpose such as evaluation of fetal or embryonic cardiac activity, fetal position, or amniotic fluid volume.
  • 8. A limited follow-up examination may be appropriate for re-evaluation of fetal size or interval growth or to re-evaluate abnormalities previously noted if a complete prior examination is on record. While this practice parameter describes the key elements of standard sonographic examinations in the first trimester and second and third trimesters, a more detailed anatomic examination of the fetus may be necessary in some cases, such as when an abnormality is found or suspected on the standard examination or in pregnancies at high risk for fetal anomalies.
  • 9. In some cases, other specialized examinations may be necessary as well. While it is not possible to detect all structural congenital anomalies with diagnostic ultrasound, adherence to the following practice parameters will maximize the possibility of detecting many fetal abnormalities.
  • 11. A. First Trimester Ultrasound Examination A standard obstetrical sonogram in the first trimester includes evaluation of the presence, size, location, and number of gestational sac(s). The gestational sac is examined for the presence of yolk sac and embryo/fetus. When an embryo/fetus is detected, it should be measured and cardiac activity recorded by 2D video clip or Mmode. Use of spectral Doppler is discouraged. The uterus, cervix, adnexa, and culde sac region should be examined.
  • 12. A standard obstetrical sonogram in the second or third trimester includes an evaluation of fetal presentation, amniotic fluid volume, cardiac activity, placental position, fetal biometry, and fetal number, plus an anatomic survey. The maternal cervix and adnexa should be examined as clinically appropriate when technically feasible. B. Standard Second or Third Trimester Examination
  • 13. A limited examination is performed when a specific question requires investigation. For example, in most routine nonemergency cases a limited examination could be performed to confirm fetal heart activity in a bleeding patient, or to verify fetal presentation in a laboring patient. In most cases limited sonographic examinations are appropriate only when a prior complete examination is on record. C. Limited Examination
  • 14. A detailed anatomic examination is performed when an anomaly is suspected on the basis of history, biochemical abnormalities, or the results of either the limited or standard scan. Other specialized examinations might include fetal Doppler ultrasound, biophysical profile, fetal echocardiogram, or additional biometric measurements. D. Specialized Examinations
  • 15. WRITTEN REQUEST FOR THE EXAMINATION The written or electronic request for an obstetrical ultrasound examination should provide sufficient information to demonstrate the medical necessity of the examination and allow for its proper performance and interpretation. Documentation that satisfies medical necessity includes 1) signs and symptoms and/or 2)
  • 16. WRITTEN REQUEST FOR THE EXAMINATION relevant history (including known diagnoses). Additional information regarding the specific reason for the examination or a provisional diagnosis would be helpful and may at times be needed to allow for the proper performance and interpretation of the examination. The request for the examination must be originated by a physician or other appropriately licensed health care provider. The accompanying clinical information should be provided by a physician or other appropriately licensed health care provider familiar with the patient’s clinical problem or question and consistent with the state’s scope of practice requirements
  • 18. A. First Trimester Ultrasound Examination 1. Indications Indications for first trimester3 sonography include: a. Confirmation of the presence of an intrauterine pregnancy . b Evaluation of a suspected ectopic pregnancy . c. Defining the cause of vaginal bleeding. d. Evaluation of pelvic pain. e. Estimation of gestational (menstrual4) age. f. Diagnosis or evaluation of multiple gestations. g. Confirmation of cardiac activity.
  • 19. A. First Trimester Ultrasound Examination 1. Indications Indications for first trimester3 sonography include: h. Imaging as an adjunct to chorionic villus sampling, embryo transfer, and localization and removal of an intrauterine device (IUD). i. Assessing for certain fetal anomalies, such as anencephaly, in high risk patients. j. Evaluation of maternal pelvic masses and/or uterine abnormalities. k. Measuring the nuchal translucency (NT) when part of a screening program for fetal aneuploidy. l. Evaluation of suspected hydatidiform mole
  • 20. A. First Trimester Ultrasound Examination Scanning in the first trimester may be performed either transabdominally or transvaginally. If a transabdominal examination is not definitive, a transvaginal scan or transperineal scan should be performed whenever possible 2. Imaging parameters
  • 21. A. First Trimester Ultrasound Examination a. The uterus, (including the cervix), and adnexa should be evaluated for the presence of a gestational sac. If a gestational sac is seen, its location should be documented. The gestational sac should be evaluated for the presence or absence of a yolk sac or embryo, and the crown- rump length should be recorded, when possible
  • 22. A definitive diagnosis of intrauterine pregnancy can be made when an intrauterine gestational sac containing a yolk sac or embryo/fetus with cardiac activity is visualized. A small, eccentric intrauterine fluid collection with an echogenic rim can be seen before the yolk sac and embryo are detectable in a very early intrauterine pregnancy. In the absence of sonographic signs of ectopic pregnancy, the fluid collection is highly likely to represent an intrauterine gestational sac. In this circumstance, the intradecidual sign may be helpful. a. The uterus
  • 23. Follow-up sonography and/or serial determination of maternal serum HCG (human chorionic gonadotropin) levels are appropriate in pregnancies of undetermined location to avoid inappropriate intervention in a potentially viable early pregnancy. The crown-rump length is a more accurate indicator of gestational (menstrual) age than is mean gestational sac diameter. However, the mean gestational sac diameter may be recorded when an embryo is not identified. Caution should be used in making the presumptive diagnosis of a gestational sac in the absence of a definite embryo or yolk sac. Without these findings an intrauterine fluid collection could represent a pseudo-gestational sac associated with an ectopic pregnancy a. The uterus
  • 24. b. Presence or absence of cardiac activity should be documented with 2D video clip or M-mode. With transvaginal scans, while cardiac motion is usually observed when the embryo is 2 mm or greater in length, if an embryo less than 7 mm in length is seen without cardiac activity, a subsequent scan in one week is recommended to ensure that the pregnancy is nonviable
  • 25. c. Fetal number should be documented. Amnionicity and chorionicity should be documented for all multiple gestations when possible.
  • 26. d. Embryonic/fetal anatomy appropriate for the first trimester should be assessed. For those patients desiring to assess their individual risk of fetal aneuploidy, a very specific measurement of the NT during a specific age interval is necessary (as determined by the laboratory used). See the guidelines for this measurement below. e. The nuchal region should be imaged, and abnormalities such as cystic hygroma should be documented.
  • 27. NT measurements should be used (in conjunction with serum biochemistry) to determine the risk for having a fetus with aneuploidy or other anatomical abnormalities such as heart defects. In this setting, it is important that the practitioner measure the NT according to established guidelines for measurement. A quality assessment program is recommended to ensure that false-positive and false-negative results are kept to a minimum e. The nuchal region should be imaged, and abnormalities such as cystic hygroma should be documented.
  • 28. i. The margins of the NT edges must be clear enough for proper placement of the calipers. ii. The fetus must be in the midsagittal plane. iii. The image must be magnified so that it is filled by the fetal head, neck, and upper thorax. Guidelines for NT measurement:
  • 29. iv. The fetal neck must be in a neutral position – not flexed and not hyperextended. v. The amnion must be seen as separate from the NT line. vi. The (+) calipers on the ultrasound must be used to perform the NT measurement. Guidelines for NT measurement:
  • 30. vii. Electronic calipers must be placed on the inner borders of the nuchal line with none of the horizontal crossbar itself protruding into the space. viii. The calipers must be placed perpendicular to the long axis of the fetus. Guidelines for NT measurement:
  • 33. Nuchal translucency “Nuchal translucency translucency-based screening for fetal abnormalities has truly become an indispensable aspect of contemporary obstetric practice.” (dr.Soha Said, Clinical Obstetrics and Gynecology, March 2008)
  • 34. Topics: Definition of Nuchal Translucency Measurement Criteria NT in Trisomy 21 Screening Advantages/Limitations of NT Screening Differential Diagnosis of Increased NT Mechanisms of Increased NT Fetal Anomalies associated with Increased NT Follow-up on Our Patients
  • 58. f. The uterus including the cervix, adnexal structures, and cul-de-sac Abnormalities should be imaged and documented.The presence, location, appearance, and size of adnexal masses should be documented. The presence and number of leiomyomata should be documented. The measurements of the largest or any potentially clinically significant leiomyomata should be documented. The cul-de-sac should be evaluated for the presence or absence of fluid. Uterine anomalies should be documented.
  • 59. Indications for second and third trimester sonography include, but are not limited to: a. Screening for fetal anomalies . b. Evaluation of fetal anatomy. c. Estimation of gestational (menstrual) age. d. Evaluation of fetal growth. e. Evaluation of vaginal bleeding. f. Evaluation of abdominal or pelvic pain. g. Evaluation of cervical insufficiency. h. Determination of fetal presentation. i. Evaluation of suspected multiple gestation. j. Adjunct to amniocentesis or other procedure. k. Evaluation of significant discrepancy between uterine size and clinical dates. l. Evaluation of pelvic mass. B. Second and Third Trimester Ultrasound Examination 1. Indications
  • 60. Indications for second and third trimester sonography include, but are not limited to: m. Evaluation of suspected hydatidiform mole. n. Adjunct to cervical cerclage placement. o. Suspected ectopic pregnancy. p. Suspected fetal death. q. Suspected uterine abnormality. r. Evaluation of fetal well-being. s. Suspected amniotic fluid abnormalities. t. Suspected placental abruption. u. Adjunct to external cephalic version. v. Evaluation of premature rupture of membranes and/or premature labor. w. Evaluation of abnormal biochemical markers. x. Follow-up evaluation of a fetal anomaly. y. Follow-up evaluation of placental location for suspected placenta previa. z. History of previous congenital anomaly. B. Second and Third Trimester Ultrasound Examination 1. Indications
  • 61. Abnormal heart rate and/or rhythm should be documented. Multiple gestations require the documentation of additional information: chorionicity, amnionicity,comparison of fetal sizes, estimation of amniotic fluid volume (increased, decreased, or normal) in each gestational sac, and fetal genitalia (when visualized). B. Second and Third Trimester Ultrasound Examination a. Fetal cardiac activity, fetal number, and presentation should be documented.
  • 62. Although it is acceptable for experienced examiners to qualitatively estimate amniotic fluid volume, semi quantitative methods have also been described for this purpose (e.g., amniotic fluid index, single deepest pocket, two-diameter pocket) 2. Imaging parameters B. Second and Third Trimester Ultrasound Examination b. A qualitative or semi quantitative estimate of amniotic fluid volume should be documented.
  • 63. The umbilical cord should be imaged, and the number of vessels in the cord documented. The placental cord insertion site .should be documented when technically possible . It is recognized that apparent placental position early in pregnancy may not correlate well with its location at the time of delivery. Transabdominal, transperineal, or transvaginal views may be helpful in visualizing the internal cervical os and its relationship to the placenta. Transvaginal or transperineal ultrasound may be considered if the cervix appears shortened or cannot be adequately visualized during the transabdominal sonogram [29,30]. A velamentous (also called membranous) placental cord insertion that crosses the internal os of the cervix is vasa previa, a condition that has a high risk of fetal mortality if not diagnosed prior to labor 2. Imaging parameters B. Second and Third Trimester Ultrasound Examination c. The placental location, appearance, and relationship to the internal cervical os should be documented.
  • 64. First-trimester crown-rump measurement is the most accurate means for sonographic dating of pregnancy. Beyond this period, a variety of sonographic parameters such as biparietal diameter, abdominal circumference, and femoral diaphysis length can be used to estimate gestational (menstrual) age. The variability of gestational (menstrual) age estimation, however, increases with advancing pregnancy. Significant discrepancies between gestational (menstrual) age and fetal measurements may suggest the possibility of fetal growth abnormality, intrauterine growth restriction, or macrosomia 2. Imaging parameters B. Second and Third Trimester Ultrasound Examination d. Gestational (menstrual) age assessment
  • 65. The pregnancy should not be redated after an accurate earlier scan has been performed and is available for comparison. i. Biparietal diameter is measured at the level of the thalami and cavum septi pellucidi or columns of the fornix. The cerebellar hemispheres should not be visible in this scanning plane. The measurement is taken from the outer edge of the proximal skull to the inner edge of the distal skull. 2. Imaging parameters B. Second and Third Trimester Ultrasound Examination d. Gestational (menstrual) age assessment
  • 66. The head shape may be flattened (dolichocephaly) or rounded (brachycephaly) as a normal variant. Under these circumstances, certain variants of normal fetal head development may make measurement of the head circumference more reliable than biparietal diameter for estimating gestational (menstrual) age. ii. Head circumference is measured at the same level as the biparietal diameter, around the outer perimeter of the calvarium. This measurement is not affected by head shape. 2. Imaging parameters B. Second and Third Trimester Ultrasound Examination d. Gestational (menstrual) age assessment
  • 67. iii. Femoral diaphysis length can be reliably used after 14 weeks gestational (menstrual) age. The long axis of the femoral shaft is most accurately measured with the beam of insonation being perpendicular to the shaft, excluding the distal femoral epiphysis. iv. Abdominal circumference or average abdominal diameter should be determined at the skin line on a true transverse view at the level of the junction of the umbilical vein, portal sinus, and fetal stomach when visible. Abdominal circumference or average abdominal diameter measurement is used with other biometric parameters to estimate fetal weight and may allow detection of intrauterine growth restriction or macrosomia. 2. Imaging parameters B. Second and Third Trimester Ultrasound Examination d. Gestational (menstrual) age assessment
  • 68. Fetal weight can be estimated by obtaining measurements such as the biparietal diameter, head circumference, abdominal circumference or average abdominal diameter, and femoral diaphysis length. Results from various prediction models can be compared to fetal weight percentiles from published nomograms B. Second and Third Trimester Ultrasound Examination e. Fetal weight estimation
  • 69. If previous studies have been performed, appropriateness of growth should also be documented. Scans for growth evaluation can typically be performed at least 2 to 4 weeks apart. A shorter scan interval may result in confusion as to whether measurement changes are truly due to growth as opposed to variations in the technique itself. B. Second and Third Trimester Ultrasound Examination e. Fetal weight estimation
  • 70. Currently, even the best fetal weight prediction methods can yield errors as high as ±15 percent. This variability can be influenced by factors such as the nature of the patient population, the number and types of anatomic parameters being measured, technical factors that affect the resolution of ultrasound images, and the weight range being studied. B. Second and Third Trimester Ultrasound Examination e. Fetal weight estimation
  • 71. Evaluation of the uterus, adnexal structures, and cervix should be performed when appropriate. If the cervix cannot be visualized, a transperineal or transvaginal scan may be considered when evaluation of the cervix is needed.This will allow recognition of incidental findings of potential clinical significance. The presence,location, and size of adnexal masses and the presence of at least the largest and potentially clinically significant leiomyomata should be documented. It is not always possible to image the normal maternal ovaries during the second and third trimesters. B. Second and Third Trimester Ultrasound Examination f. Maternal anatomy
  • 72. • g. Fetal anatomic survey • Fetal anatomy, as described in this document, may be adequately assessed by ultrasound after approximately 18 weeks gestational (menstrual) age. It may be possible to document normal structures before this time, although some structures can be difficult to visualize due to fetal size,position, movement, abdominal scars, and increased maternal abdominal wall thickness]. Asecond or third trimester scan may pose technical limitations for an anatomic evaluation due to imaging artifacts from acoustic shadowing. When this occurs, the report of the sonographic examination should document the nature of this technical limitation. A follow-up examination may be helpful. 2. Imaging parameters B. Second and Third Trimester Ultrasound Examination
  • 73. • g. Fetal anatomic survey • The following areas of assessment represent the minimal elements of a standard examination of fetal anatomy. A more detailed fetal anatomic examination may be necessary if an abnormality or • suspected abnormality is found on the standard examination. • i. Head, face, and neck • Lateral cerebral ventricles • Choroid plexus • Midline falx • Cavum septi pellucidi • Cerebellum • Cistern magna • Upper lip • A measurement of the nuchal fold may be helpful during a specific age interval to assess the risk of • aneuploidy B. Second and Third Trimester Ultrasound Examination
  • 74. REFERENCES 1. Barnett SB, Ter Haar GR, Ziskin MC, Rott HD, Duck FA, Maeda K. International recommendations and guidelines for the safe use of diagnostic ultrasound in medicine. Ultrasound Med Biol 2000;26:355-366. 2. Bly S, Van den Hof MC. Obstetric ultrasound biological effects and safety. J Obstet Gynaecol Can 2005;27:572-580. 3. Barnhart K, van Mello NM, Bourne T, et al. Pregnancy of unknown location: a consensus statement of nomenclature, definitions, and outcome. Fertil Steril 2011;95:857-866. 4. Jeve Y, Rana R, Bhide A, Thangaratinam S. Accuracy of first-trimester ultrasound in the diagnosis of early embryonic demise: a systematic review. Ultrasound Obstet Gynecol 2011;38:489-496. 5. Thilaganathan B. The evidence base for miscarriage diagnosis: better late than never. Ultrasound Obstet Gynecol 2011;38:487-488. 6. Chambers SE, Muir BB, Haddad NG. Ultrasound evaluation of ectopic pregnancy including correlation with human chorionic gonadotrophin levels. Br J Radiol 1990;63:246-250. 7. Hill LM, Kislak S, Martin JG. Transvaginal sonographic detection of the pseudogestational sac associated with ectopic pregnancy. Obstet Gynecol 1990;75:986-988. 8. Kirk E, Daemen A, Papageorghiou AT, et al. Why are some ectopic pregnancies characterized as pregnancies of unknown location at the initial transvaginal ultrasound examination? Acta Obstet Gynecol Scand 2008;87:1150-1154. 9. Laing FC, Frates MC. Ultrasound evaluation during the first trimester of pregnancy. In: Ultrasonography in obstetrics and gynecology. 4th ed. Philadelphia, PA: WB Saunders; 2000:105-145.
  • 75. Guidelines for the Performance of First Trimester Ultrasound
  • 76. • Studies should be performed using an abdominal and/or vaginal approach. A high frequency transducer should be used and the equipment should be operated with the lowest ultrasonic exposure settings capable of providing the necessary diagnostic information. A vaginal transducer should always be available and a transvaginal scan should be offered to the patient when it is anticipated that this would result in a more diagnostic study. The patient may choose to accept or refuse this offer and undue persuasion is inappropriate.
  • 77. GESTATION SAC • The gestation sac should usually be visible from four and one half (4.5) to five (5) weeks using high frequency transvaginal ultrasound. • When a gestation sac like structure is seen but no live fetus demonstrated, it is important to attempt to ensure that it is not a 'pseudo gestational sac'. Look for the echogenic trophoblast rim and the yolk sac, and ensure that the fluid in the gestation sac is echo free.
  • 78. • If a gestation sac is not visible in the uterus of a patient believed to be pregnant, the adnexa should be carefully examined looking for evidence suggesting the presence of an ectopic pregnancy - most ectopics can be suspected with high frequency transvaginal ultrasound. • In a patient with a positive pregnant test but either - • • no gestational sac is seen within the uterus or elsewhere in the pelvis • • an apparent sac is seen but no fetal structures (including yolk sac) or heart movements are visible
  • 79. GESTATIONAL AGE • This is most accurately assessed in the first trimester. The earlier the crown rump length (CRL) is measured, the more accurate is the assessment of gestational age. The CRL can be measured from six weeks gestation. The composite CRL chart in the ASUM Policies and Statements folder is recommended. From eleven weeks multiparameter assessment can be used. Biparietal diameter (BPD) is the most often used second measurement
  • 80. FETAL HEART MOVEMENTS • With a high resolution vaginal transducer, fetal heart movements are often visible from five (5) to six (6) weeks (i.e. CRL = 2mm), but may not be seen until CRL = 3-4mm
  • 81. PREGNANCY FAILURE • An experienced operator using high quality transvaginal equipment may diagnose pregnancy failure under either or both of the following circumstances: • 1. When no live fetus is visible in a gestation sac and the mean sac diameter (MSD) cut off >25mm. • 2. When there is a visible fetus with a CRL cut off >7mm but no fetal heart movements can be demonstrated. The area of the fetal heart should be observed for a prolonged period of at least thirty (30) seconds to ensure that there is no cardiac activity. • In situations where pregnancy failure is suspected by an operator who either does not have extensive experience in making the diagnosis or does not have access to high quality equipment or if there is any doubt about the viability of the fetus, a second opinion or a review scan in one week .
  • 82. NUCHAL TRANSLUCENCY • The nuchal translucency measurement is a test to assess the risk of chromosomal abnormality, in particular of trisomy 21. The measurement may also be abnormal in other fetal anomalies (e.g. some congenital heart disease). It has been estimated that first trimester screening by a combination of sonography and material serum testing of PAPP-A and free βhCG can potentially identify 94% of trisomy 21 fetuses with a false positive rate of 5%.
  • 83. • The nuchal translucency measurement may be performed at the request of the referring Medical Practitioner. Due consideration should be given as to how and who is going to counsel the patient prior to the performance of a nuchal translucency scan.
  • 84. • Method of measurement: • 1. The nuchal translucency should be measured on a sagittal midline scan through the fetus. • 2. The fetus should be in neutral position and occupy at least 75% of the image. • 3. The amnion should be seen separate to the fetal skin line. • 4. Calipers should be positioned to measure the maximum diameter of the fluid at the back of the neck.
  • 85. OVARIES, UTERUS AND ADNEXA • Each ovary should be examined. The corpus luteum can vary greatly in appearance during the first (and early second) trimesters of pregnancy. Sonographic appearances include a solid, rounded target like lesion or a predominately cystic structure. Peripheral vascularity is usually detectable. • The size of a corpus luteum is also variable, commonly measuring up to 3cm.
  • 86. • Larger or unusual masses should assessed as in the non pregnant woman. • The uterus should be examined for evidence of a fibroids or uterine developmental defects. The uterine position should also be noted (anteverted, axial, retroverted). • The adnexa should be examined for coexistent ectopics and free fluid.
  • 87. REFERENCES • 1. Hately, Case and Campbell. Establishing the death of an embryo by ultrasound. Ultrasound Obstet. Gynecol.5 (1995) 353-357 • 2. Nicolaides KH Am. J. Obstet. Gynecol. (2004) 191:45-47 • 3. From Nicolaides group: Snijders et al. Assessmant of risk of Trisomy 21 by maternal age and fetal nuchal-translucency thickness.
  • 89. • Antenatal fetal monitoring is a routine part of antenatal care in that fetal growth is assessed by palpation of uterine and enquiries as to • whether the baby is active assess fetal wellbeing. These take place at every antenatal check. In most pregnancies this is an adequate measure of fetal well being but on occasions when there is concern regarding a specific aspect of fetal wellbeing more detailed monitoring is necessary.
  • 90. Indications Situations which may require more detailed fetal monitoring include:
  • 91. A. Maternal hypertension • Hypertension in pregnancy is not a single entity but comprises: • Chronic (essential) hypertension which complicates 1 – 5 % of pregnancies and is defined as a blood pressure greater that 140/90 millimetres of mercury that either pre-dates pregnancy or develops before 20 weeks of gestation. • Pregnancy induced hypertension which develops after 20 weeks of gestation and complicates 5 – 10% of pregnancies • Pre-eclampsia which is pregnancy induced hypertension in association with proteinuria or oedema or both.
  • 92. B. Reduced fetal activity • The perception of fetal movement by an expectant mother is extremely variable. However, during the second half of pregnancy most women are aware of fetal movements and can appreciate when the frequency of movements reduces significantly. All women should be asked to pay attention to the frequency of fetal movements during the latter stages of pregnancy. This is however, particularly important where there has been an adverse outcome to a previous pregnancy or where there is a suspicion of intrauterine growth restriction in the present pregnancy. 55% of women experiencing a still birth had perceived a reduction of fetal movements prior to the diagnosis.
  • 93. C. Suspected small for gestational age (SGA) fetus • The absolute size of a baby at any given gestation is an unreliable indicator of health and well being. The nearer to term the greater is the natural variation in the size/weight of baby. Some will be constitutionally smaller or larger than average. Others may be of an average weight but not have reached the growth potential for that particular fetus. For these reasons the rate of growth is far more important than any one single measurement. A series of ultrasound measurements is therefore required which should be plotted on the charts in the antenatal notes. Deviation from the normal growth curve, particularly of the abdominal circumference may be an indication of fetal compromise.
  • 94. D. Previous stillbirth / neonatal death • Whether or not women are at increased risk of an adverse outcome will depend upon the cause of the previous stillbirth or neonatal death. Where extreme prematurity is implicated strategies to detect/prevent the onset of pre-term labour will be required. Where unexplained fetal loss has occurred late in pregnancy close monitoring and elective delivery before term are usually advised.
  • 95. E. Post maturity • Patients where the pregnancy is still ongoing more than 2 weeks after the agreed due date but whose pregnancy is otherwise uncomplicated require additional fetal monitoring .Reasons for this may include: - • Patient declines induction of labour • No appointment slots are available for induction of labour • Cervix is unfavourable and patient and obstetrician prefer to delay induction of labour.
  • 97. The purpose of this guideline •is to assist all healthcare professionals in the management of first trimester spontaneous miscarriage.
  • 98. What is a Threatened Miscarriage? • A threatened miscarriage is a pregnancy where vaginal bleeding has taken place but an ultrasound has shown a healthy fetus and fetal heartbeat. The bleeding can be very varied and can occur at any time after a missed period. It can range from being a smear of pink, brown or red loss on the toilet paper to heavy vaginal bleeding similar or even heavier than a period. The diagnosis of a threatened miscarriage is made when you attend for an ultrasound scan and as long as you are at least 6 weeks pregnant the ultrasound should be able to visualise your tiny baby and show a healthy heartbeat. It may be necessary to demonstrate by performing an internal vaginal scan.
  • 99. • Sometimes the scan may show up a small haematoma (blood clot) around the pregnancy sac but very often nothing abnormal is seen and it is difficult to explain why the bleeding has occurred. The bleeding may have come from the implantation site which is when the placenta of your baby burrows itself into the lining of the womb. This process may cause some bleeding. If we can see a baby‟s heartbeat on ultrasound it is very likely that your pregnancy will continue with success rates exceeding 95%.
  • 100. • If there is a collection of blood around the pregnancy sac or the bleeding continues, it may be appropriate to repeat an ultrasound scan in 1-2 weeks. In any case the heartbeat will be checked at your first booking visit in the hospital. If the bleeding settles down there is probably no need for a further scan unless you have further anxieties. Traditionally bed rest has been advised for mothers with threatened miscarriage but all the evidence would suggest that this does not prevent miscarriage. It may help some patients psychologically to rest in bed but it is not necessary. Unfortunately there is no specific treatment to stop the bleeding and if you do adopt bed rest there is the possibility that on standing up bleeding may become heavier due to pooling of blood in the vagina that results from lying down.
  • 101. • Spontaneous miscarriage is the commonest complication of pregnancy. It occurs in up to 20% of clinical pregnancies equating to approximately 15,000 miscarriages per annum in Ireland. • This guideline provides information relating to the diagnosis of early pregnancy loss defined as a loss, within the first 13 weeks of pregnancy. It specifically addresses the ultrasound diagnosis of miscarriage. This guideline is intended to be primarily used by health personnel working in the area of early pregnancy which includes obstetricians, midwife sonographers, radiographers, radiologists and general practitioners. All of the groups should be familiar with the various diagnostic tools necessary to help delineate a viable from a non-viable pregnancy.
  • 102. Ultrasound and Embryo Development • It is important that all relevant health personnel are familiar with the chronological ultrasound features of early pregnancy. The first ultrasound evidence of pregnancy is the gestational sac within the thickened decidua. This sac which represents the chorionic cavity is a small anechoic fluid collection surrounded by an echogenic ring that represents trophoblasts and decidual reaction. It is possible to identify the sac with transvaginal ultrasound by 4 weeks and 2 days when the mean diameter is 2-3 mm.
  • 103. • The yolk sac is the first structure often seen within the gestational sac and it confirms an intrauterine pregnancy. The yolk sac is first seen by transvaginal ultrasound when the mean gestational sac diameter is ≥5 mm, and should always be visualised when the mean gestational sac diameter is >7 mm. The amnion is a thin, rounded membrane surrounding the embryo and is completely enveloped by the thick echogenic chorion.
  • 104. • The yolk sac is situated between the amnion and the chorion. The amnion is thin and difficult to visualise and is best seen when perpendicular to the ultrasound beam. The amnion grows rapidly during pregnancy and fuses with the chorion between 12 and 16 weeks gestation. The embryo can be identified by transvaginal ultrasound when as small as 1–2 mm in length. At 5–7 weeks gestation both the embryo and gestational sac should grow at approximately 1 mm per day.
  • 105. • Cardiac activity immediately adjacent to the yolk sac indicates a live embryo but may not be seen until the embryo measures 5 mm. From 5 ½ - 6 ½ weeks gestation a fetal heart rate of less than 100 beats per minute is normal. During the following 3 weeks there is a rapid increase up to 180 beats per minute.
  • 107. Ultrasound Determination of Pregnancy Loss • If on transvaginal ultrasound, the mean gestational sac diameter is less than 20mm with no yolk sac or embryo, or if the fetal pole is less than 8mm with no cardiac activity identified within 30 seconds, then the diagnosis of pregnancy of uncertain viability may be made. A repeat ultrasound examination should be arranged after 7-10 days to clarify the diagnosis.
  • 108. • An ultrasound diagnosis of fetal demise may be made when there is no fetal heart in a fetus with fetal pole >7mm when using transvaginal ultrasound. A diagnosis of pregnancy loss may also be made if the mean gestational sac diameter exceeds 20 mm in the absence of a yolk sac or embryo. Particular care should be taken to scan all of the sac in a longitudinal and vertical plain. The mean sac diameter should be measured in 3 diameters and averaged. The area of the fetal heart should be observed for a prolonged period of at least 30 seconds to ensure that there is no cardiac activity. The use of transvaginal ultrasound should be encouraged as better visualisation is nearly always possible.
  • 109. • Different cutoffs for diagnosing miscarriage apply when using transabdominal ultrasound. If transvaginal ultrasound is not available or not acceptable to a woman, transabdominal ultrasound criteria for fetal demise can be made when there is no fetal heart in an embryo measuring >8 mm. Similarly, if the mean gestational sac diameter is > 25 mm in the absence of a yolk sac or embryo, a diagnosis of fetal demise can be made using transabdominal ultrasound. If there is no sign of either intra or extra-uterine pregnancy or retained products in a woman with a positive pregnancy test, this should be described as a pregnancy of unknown location.
  • 110. • It is not essential for a second sonographer to confirm fetal demise, provided that the first sonographer is appropriately qualified and has adhered to the guidelines. It may be distressing for the woman to undergo another unnecessary transvaginal assessment. It should, however, be emphasised that if there is any doubt in the diagnosis, a second opinion should be sought. Also, if a second opinion may benefit a woman psychologically, it should be facilitated. It is important to listen carefully to the views of the woman, particularly in circumstances where she has had a prior pregnancy.
  • 113. Prediction of Early Pregnancy Failure • There are certain ultrasound features which predict but are not diagnostic of early pregnancy failure. These include a fetal heart rate of less than 85 beats per minute at greater than 7 weeks gestation, a small sac size relative to the embryo (difference of less than 5 mm between gestation sac and crown rump length), enlarged or abnormally shaped yolk sac and sub- chorionic haematoma. The latter leads to a pregnancy loss rate of about 9%. This risk would appear to be increased in women older than 35 years and in pregnancies less than 8 weeks gestation. • Any clinical interventions, however, must be based on diagnostic and not predictive features.
  • 114. Common Pitfalls with Ultrasound in Early Pregnancy • Exercise extreme caution with regard to last menstrual period (LMP) on history taking. Up to 50% of women are uncertain of their dates, or have an irregular cycle, or have just stopped the oral contraceptive pill (OCP), or are lactating or did not have a normal last period Enquire when the women had her first positive pregnancy test (which may be positive 3 days before the missed period).
  • 115. • Visualise all of the uterus. Pan the uterus in saggital, and then rotate the probe 90 degrees to visualise from cervix to fundus. Failure to visualise all of the uterus will result in missing gestational sacs in multiple pregnancies. • Neglecting to scan the adnexae will result in missing hererotopic pregnancies and ovarian masses which may require surgery.
  • 116. • Avoid labelling subchorionic bleeds as additional gestational sacs. Do not tell a woman that she has a twin pregnancy with one empty sac unless you are very experienced in ultrasound. • Pseudosacs. Exercise caution in labelling intrauterine sac–like structures as gestational sacs unless they have contents i.e. yolk sac or fetus. Pseudosacs will follow the uterine cavity and are more ellipitical, while gestational sacs are fundal and eccentrically placed.
  • 117. • Fibroid Uterus. The fundus of a fibroid uterus may not be included in the scan field at TVS. Both TVS and abdominal scans are needed in these women to avoid missing gestational sacs.
  • 118. Women who should be assessed at an early pregnancy unit include: • Those with a history of a positive pregnancy test and: • Vaginal bleeding and / or abdominal pain • Previous ectopic pregnancy • Previous tubal surgery • Previous miscarriage • Intrauterine contraceptive device in situ • Persistent bleeding post evacuation of the retained products of conception (ERPC) where there is a suspicion of problems • Other clinical indications as agreed in each hospital
  • 119. The sonographer should produce reports using standardised documentation. This includes: • Presence or absence of an intrauterine gestational sac(s) • Number of sacs and mean gestational sac size • Presence of haematoma • Yolk sac • Fetal Pole • Crown Rump Length (CRL) with expected gestation • Fetal heart pulsation present or absent • Extrauterine observation to include ovaries, adnexal mass / fluid in the Pouch of Douglas
  • 121. Three-dimensional Ultrasound Imaging Three-dimensional ultrasound (3DUS) has become an increasingly important component of clinical imaging. While early applications have been focused on cardiac, obstetric, and gynecologic applications its capabilities continue to expand throughout the clinical arena. This expansion is driven by important improvements in technology, image quality and clinical ease of use. This chapter will provide a brief review of the technology behind 3D and 4D ultrasound imaging, clinical considerations in acquiring, displaying and analyzing 3D/4D ultrasound data and the clinical contributions this exciting technology is making.
  • 122. • Ultrasound is a versatile imaging technique that can reveal the internal structure of organs, often with astounding clarity. • Ultrasound is unique in its ability to image patient anatomy and physiology in real time, providing an important, rapid and noninvasive means of evaluation. Ultrasound continues to make significant contributions to patient care by reassuring patients and enhancing their quality of life by helping physicians • understand their anatomy in ways not possible with other techniques.
  • 123. • Three-dimensional ultrasound (3DUS) is an increasingly important area of ultrasound development . 3DUS exploits the real-time capability of ultrasound to build a volume that can then be explored using increasingly affordable high performance workstations. 3DUS is a logical evolution of ultrasound technology and complements other parallel developments underway at this time, including harmonic imaging and the development of ultrasound contrast materials.
  • 124. EQUIPMENT DESIGN • Design of clinically useful scanning equipment is crucially • dependent on having an easy-to-use system that provides rapid feedback to the clinician user in a straightforward manner. • While superb image quality is expected, it also is important • to avoid an overabundance of bells and whistles that often • distract and overwhelm users rather than enhance the clinical • imaging experience. Fundamental to an optimal operational • environment is a highly functional, ergonomically designed • user interface (Fig. 1). Selection of scanner features should • be task related, obvious and context dependent.
  • 127. ACQUISITION APPROACHES • Acquisition of a data volume requires significant computing resources to process the acoustic and position data rapidly and create a volume. Various strategies are available in clinical scanners with most directed toward providing ”real-time” images to the clinical user. • Among the primary approaches employed are free-hand scanning with and without position sensing, mechanical devices integrated into the transducer and matrix array technology(Fig. 3).
  • 129. DISPLAY STRATEGIES • Visualization of the relevant patient anatomy will ultimately determine the clinical utility of 3DUS. Although traditional methods of viewing multi-planar images provide much information , volume rendering for visualization of underlying patient anatomy including blood flow offers new ways to visualize complex anatomy in a single image and to enhance the visibility of structures that previously were difficult to appreciate.
  • 130. • Visualization depends on optimised algorithms to display the structure of interest and fast computing hardware to display the results fast enough to interactively adjust parameters or viewing orientation. Volume data currently are displayed using two primary methods: these are a series of multi- planar images (typically three slices that are orthogonal to each other),and rendered images that show entire structures throughout the volume (Fig. 6).
  • 133. In the fetus, improved visualization of fetal features, including: • the face and limbs, has improved anomaly identification and been immediately appealing for clearly sharing development information with the family. • Cardiac applications have provided a surgeon’s eye view using transesophageal and transthoracic techniques to assess valve geometry and motion and to plan operative procedures. • Fetal cardiac imaging has become an increasingly important part of prenatal diagnosis as a result of the development of • four-dimensional imaging methods Gynecological applications include evaluating congenital anomalies of the uterus, endometrial cancer, adnexal masses,intrauterine device position and follicular cysts. With 3DUS, it is possible to obtain the coronal plane of the uterus (Fig. 11), which is not possible with 2DUS. This view greatly facilitates identification of uterine anatomy, which can be important in managing infertility and congenital anomalies
  • 159. What are 3D and 4D ultrasound scans?
  • 160. 3D scans show still pictures of your baby in three dimensions. 4D scans show moving 3D images of your baby, with time being the fourth dimension. It's natural to be really excited by the prospect of your first scan. But some mums find the standard 2D scans disappointing when all they see is a grey, blurry outline. This is because the scan sees right through your baby, so the photos show her internal organs.
  • 161. With 3D and 4D scans, you see your baby's skin rather than her insides. You may see the shape of your baby's mouth and nose, or be able to spot her yawning or sticking her tongue out.
  • 162. -3D and 4D scans are considered as safe as 2D scans, because the images are made up of sections of two-dimensional images converted into a picture. However, experts do not recommend having 3D or 4D scans purely for a souvenir photo or recording, because it means that you are exposing your baby to more ultrasound than is medically necessary. Some private ultrasounds can be as long as 45 minutes to an hour, which may be longer than recommended safety limits.
  • 163. 3D and 4D scans may nonetheless provide more information about a known abnormality. Because these scans can show more detail from different angles, they can help in the diagnosis of cleft lip. This can help doctors to plan the repair after birth. 3D scanning can also be useful to look at the heart and other internal organs. As a result, some fetal medicine units do use 3D scans, but only when they're medically necessary.
  • 164. There’s no evidence to suggest that the scans aren’t safe, and most mums-to-be gain reassurance from them. Nonetheless, any type of ultrasound scan should only be performed by a trained professional, for as short a time and at the lowest intensity, as possible. If you’d like a 3D or 4D scan you’ll probably need to arrange it privately, and pay a fee. The clinic may also give you a recording of the scan on DVD, though this is likely to cost extra.
  • 165. The special transducers and software required to do 3D and 4D scans are expensive. There are few clear medical benefits, and experts say they should only be done if there's a medical need. So it's unlikely that these scans will replace normal 2D scans used for routine maternity care in the NHS. If you decide to have one, the best time to have a 3D or 4D scan is when you're between 26 weeks and 30 weeks pregnant.
  • 166. Before 26 weeks your baby has very little fat under her skin, so the bones of her face will show through. After 30 weeks, your baby's head may go deep down in your pelvis, so you may not be able to see her face. If the placenta is at the front of your womb (uterus), known as anterior placenta, you'll get the best images of your baby if you wait until 28 weeks. It's natural that you'd like to see your baby's face on the scan. But sometimes it's not possible, depending on how she's lying.
  • 167. -If she's lying facing outwards, with a good pool of amniotic fluid around her features, you should be able to see her face clearly. But if she's facing your back, her head's far down in your pelvis, or there's not much fluid around her, you won't see much. The same applies if you have a lot of tummy fat. -The sonographer may ask you to go for a walk, or to come back in a week, when your baby may have moved to a better position. If it's not possible to get good views of her face, you may be able to see her fingers and toes instead.
  • 168. 3D and 4D ultrasound in fetal cardiac scanning
  • 169. • Over the last decade we have been witness to a burgeoning literature on three-dimensional (3D) and four-dimensional (4D) ultrasound- based studies of the fetal cardiovascular system. Recent advances in the technology of 3D/4D ultrasound systems allow almost real- time 3D/4D fetal heart scans.
  • 170. • It appears that 3D/4D ultrasound in fetal echocardiography may make a significant contribution to interdisciplinary management team consultation, health delivery systems, parental counseling, and professional training. Our aim is to review the state of the art in 3D/4D fetal echocardiography through the literature and index cases of normal and anomalous fetal hearts.
  • 171. • Three-dimensional (3D) and four- dimensional (4D) applications in fetal ultrasound scanning have made impressive strides in the past two decades. Today, many more centers have 3D/4D ultrasound capabilities at their command ,and we are witness to a burgeoning literature of 3D/4Dbased studies.
  • 172. • Perhaps in no other organ system is this recent outstanding progress so evident as in the fetal cardiovascular system. Recent technological developments of motion-gated cardiac scanning allow almost real-time 3D/4D heart examination. • It appears from this growing body of literature that 3D/4D ultrasonography can make a significant contribution to our understanding of the developing fetal heart in both normal • and anomalous cases, to interdisciplinary management team consultation, to parental counseling, and to professional training.
  • 173. • These features may work to extend the benefits of prenatal cardiac screening to poorly-served areas. • The introduction of ‘virtual planes’ to fetal cardiac scanning has helped sonographers obtain views of the fetal heart not generally accessible with a standard two-dimensional (2D) approach.
  • 174. • It is perhaps too early to evaluate whether 3D/4D cardiac scanning will improve the accuracy of fetal echocardiography programs. • However, there is no doubt that 3D/4D ultrasonography gives us another look at the fetal heart. The purpose of this review is to summarize the recent technological advances in 3D/4D fetal echocardiography , demonstrating their application through normal and anomalous cases.
  • 175. 3D/4D TECHNIQUES AND THEIR APPLICATION TO FETAL CARDIAC SCANNING • Spatio-temporal image correlation (STIC) • STIC acquisition is an indirect motion-gated offline scanning mode1–4. The automated volume acquisition is made possible by the array in the transducer performing a slow single sweep, recording a single 3D data set consisting of many 2D frames one behind the other. • The volume of interest (VOI) is acquired over a period of about 7.5 to 30 s at a sweep angle of approximately 20–40◦ (depending on the size of the fetus) and frame rate of about 150 frames per second. A 10-second, 25◦acquisition would contain 1500 B-mode images4. Following acquisition the ultrasound system applies • mathematical algorithms to process the volume data and detect systolic peaks, which are used to calculate the fetal heart rate.
  • 177. • The B-mode images are arranged in order according to their spatial and temporal domain, correlated to the internal trigger, the systolic peaks that define the heart cycle4 (Figure 1).
  • 178. • The resultant 40 consecutive volumes are a reconstructed complete heart cycle that displays in an endless loop. • This cine-like file of a beating fetal heart can be manipulated to display any acquired scanning plane at any stage in the cardiac cycle (Figure 2). • While a complex process to describe, this reconstruction takes place directly following the scan in a matter of seconds;
  • 180. • the STIC acquisition can be reviewed with the patient still present and repeated if necessary, and saved to the scanning machine or a network. Optimal STIC acquisition technique for examination of the fetal heart is thoroughly. • In post-processing, various methodologies have been proposed to optimize the acquisition to demonstrate the classic planes of fetal echocardiography (Figure 3), as well as ‘virtual planes’ that are generally inaccessible in 2D cardiac scanning.
  • 182. • These views once obtained are likewise stored in the patient’s file, in addition to the original volume, either as static images or 4D motion files. Any of the stored information can be shared for expert review, interdisciplinary consultation, parental counseling, or teaching. • STIC is an acquisition modality that can be combined with other applications by selecting the appropriate setting before acquisition (B-flow, color and power Doppler, tissue Doppler, high-definition flow Doppler) or with post processing visualization modalities (3D volume rendering, inversion mode, tomographic ultrasound imaging).
  • 183. • By moving the point the operator manipulates the volume to display any plane within the volume; if temporal information was acquired, the same plane can be displayed at any stage of the scanned cycle. • From a good STIC acquisition the operator can scroll through the acquired volume to obtain sequentially each of the classic five planes6 of fetal echocardiography, and any plane may be viewed at any time-point throughout the reconstructed cardiac cycle loop. The cycle can be run or stopped frame-by-frame to allow examination of all phases of the cardiac cycle, for example opening and closing of the atrioventricular valves.
  • 184. • By comparing the A- and B-frames of the MPR display, the operator can view complex cardiac anatomy in corresponding transverse and longitudinal planes simultaneously. So, for example, an anomalous vessel that might be disregarded in cross-section is confirmed in the longitudinal plane. • 3D rendering is another analysis capability of an acquired volume. It is familiar from static 3D applications, such as imaging the fetal face in surface rendering mode. In fetal echocardiography it is readily applied to 4D scanning.
  • 185. • The operator places a bounding box around the region of interest within the volume (after arriving at the desired plane and time) to show a slice of the volume whose depth reflects the thickness of the slice. • For example, with the A-frame showing a good four chamber view, the operator places the bounding box tightly around the interventricular septum. The rendered image in the D-frame will show an ‘en face’ view of the septum. The operator can determine whether the plane will be displayed from the left or right, i.e. the septum from within the left or the right ventricle; the thickness of • the slice will determine the depth of the final image, for example to show texture of the trabeculations within the right ventricle (Figure 4).
  • 187. • TUI is a more recent application that extends the capabilities of MPR and rendering modes. This multislice analysis mode resembles a magnetic resonance imaging or computer-assisted tomography display. Nine parallel slices are displayed simultaneously from the plane of interest (the ‘zero’ plane), giving sequential views from −4 to +4. The thickness of the slices, i.e. the distance between one plane and the next, can be adjusted by the operator. The upper left frame of the display shows the position of each plane within the region of interest, relative to the reference plane. This application has the advantage of displaying sequential parallel planes simultaneously, giving amore complete picture of the fetal heart (Figure 5).
  • 189. • 3D/4D with color Doppler, 3D power Doppler (3DPD) and 3D high definition power flow Doppler Color and power Doppler have been extensively applied to fetal echocardiography; one could hardly imagine performing a complete fetal echo scan today without color Doppler. Color or power Doppler, and the most recent development, high definition flow Doppler, can be combined with static 3D direct volume non-gated scanning to obtain a 3D volume file with color Doppler information or 3DPD (one-color) volume files. • Color Doppler can be used more effectively in 3D/4D ultrasonography when combined with STIC acquisition12 in fetal echocardiography, resulting in a volume file that reconstructs the cardiac cycle, as above, with color flow information.
  • 190. • This joins the Doppler flow to cardiac events2 and provides all the advantages of analysis (MPR, rendering, TUI) with color. This combination of modalities is very sensitive for detecting intracardiac Doppler flow through the cardiac cycle, for example mild tricuspid regurgitation that occurs very early in systole or very briefly can be clearly seen. • Extreme care must be taken when working with Doppler applications in post-processing, however, to avoid misinterpretation of flow direction as the volume is rotated.
  • 191. • 3DPD is directionless, one-color Doppler that is most effectively joined with static 3D scanning2. 3DPD uses Doppler shift technology to reconstruct the blood vessels in the VOI, isolated from the rest of the volume. Using the ‘glass body’ mode in post- processing, surrounding tissue is eliminated and the vascular portion of the scan is available in its entirety for evaluation. The operator can scroll spatially to any plane in the volume (but not temporally: in this case, color Doppler with STIC is more effective, see above).
  • 192. • 3DPD can reconstruct the vascular tree of the fetal abdomen and thorax14,15, relieving the operator of the necessity of reconstructing amental picture of the idiosyncratic course of an anomalous vessel from a series of 2D planes. • This has been shown to aid our • understanding of the normal and anomalous anatomy and pathophysiology of vascular lesions16 (Figure 6).
  • 194. • High-definition power flow Doppler, the newest development in color Doppler applications, uses high resolution and a small sample volume to produce images with two-color directional information with less ‘blooming’ of color for more realistic representation of vessel size. It depicts flow at a lower velocity than does color or power Doppler, and has the advantage of showing flow direction. It can be combined with static 3D or 4D gated acquisition (STIC) and the glass-body mode, to produce high-resolution images of the vascular tree with bidirectional color coding (Figure 7).
  • 196. • This technique is particularly sensitive for imaging small vessels. High resolution bidirectional power flow Doppler combines the flow information provided by color Doppler with the anatomic acuity associated with power Doppler. Owing to this modality’s sensitivity systolic and diastolic flow are observed at the same time, for example, when used with STIC acquisition the ductus venosus is shown to remain filled both in systole and in diastole.
  • 197. • B-flow • B-flow is an ‘old-new’ technology that images blood flow without relying on Doppler shift. B-flow is an outgrowth of B-mode imaging that, with the advent of faster frame rates and computer processing, allows the direct depiction of blood cell reflectors. It avoids some of the pitfalls of Doppler flow studies, such as aliasing and signal dropout at orthogonal scanning angles. The resulting image is a live gray-scale depiction of blood flow and part of the surrounding lumen, creating sensitive ‘digital casts’ of blood vessels and cardiac chambers (Figure 8).
  • 198. • This also makes B-flow more sensitive for volume measurement. When applied to 3D fetal echocardiography B-flow modality is a direct volume non-gated scanning method able to show blood flow in the heart and great vessels in real-time, without color Doppler flow information
  • 200. SCREENING EXAMINATION OF THE FETAL HEART WITH 3D/4D ULTRASOUND • Guidelines for the performance of fetal heart examinations have been published by the International Society of Ultrasound in Obstetrics and Gynecology (ISUOG).These guidelines for ‘basic’ and ‘extended basic’ fetal cardiac scanning are amenable to 3D/4D applications, and 3D/4D can enhance both basic and extended basic fetal cardiac scans, as well as evaluation of congenital anomalies. Many research teams have applied 3D ultrasound and STIC acquisition to fetal echocardiography, and various techniques have been put forward to optimize the use of this modality. A well-executed STIC acquisition5 contains all the necessary planes for evaluation of the five classic transverse planes of fetal echocardiography.
  • 201. • The operator can examine the fetal upper abdomen and stomach, then scroll cephalad to obtain the familiar four chamber view, the five-chamber view, the bifurcation of the pulmonary arteries, and finally the three-vessel and trachea view. Slight adjustment along the x- or y-axis may be necessary to optimize the images. Performed properly, this methodology will provide the examiner with all the necessary planes to conform with the guidelines. However, it must be remembered that STIC acquisition that has been degraded by maternal or fetal movements, including fetal breathing movements, will contain artifacts within the scan volume.
  • 202. POTENTIAL PITFALLS OF 3D/4D ECHOCARDIOGRAPHY • 3D/4D fetal echocardiography scanning is prone to artifacts similar to those encountered in 2D ultrasonography, and some that are specific to 3D/4D acquisition and post-processing.
  • 203. STIC acquisition quality • The quality of a STIC acquisition may be adversely affected by fetal body or ‘breathing’ movements; quality is improved by scanning with the fetus in a quiet state, and using the shortest scan time possible. When reviewing a STIC acquisition, the B-frame will reveal artifacts introduced by fetal breathing movements (Figure 9). If the B-frame appears sound, the volume is usually acceptable, and can be used for further investigation. It must be stressed again that the quality of the original acquisition will affect all further stages of post- processing and evaluation.
  • 205. ACCURACY • Several studies have compared imaging yield between 2D and 3D/4D fetal echocardiography, others have examined the feasibility of 3D/4D and STIC in screening programs, while others have described the application of various 3D/4D modalities to the diagnosis or evaluation of fetal cardiovascular anomalies. However, no large study has examined the contribution of 3D/4D ultrasonography to the accuracy of fetal echocardiography screening programs.
  • 206. • In coming years, studies will direct 3D/4D capabilities to the evaluation of fetal cardiac functional parameters. This may provide insights into the physiological effects of fetal structural or functional cardiac defects, or maternal diseases such as diabetes, on the developing fetus. To the best of our knowledge, no large study has been performed to date to examine whether the addition of 3D/4D methods to fetal echocardiography screening programs increases the detection rate of cardiac defects. This technology has reached the stage when its reproducibility and added value in screening accuracy should be tested in large prospective studies, not only by teams or in centers that have made 3D/4D their specialty, but among the generality of professionals performing fetal echocardiography.
  • 207. REFERENCES • 1. DeVore GR, Falkensammer P, Sklansky MS, Platt LD. Spatiotemporal image correlation (STIC): new technology for evaluation of the fetal heart. Ultrasound Obstet Gynecol 2003;22: 380–387. • 2. Deng J. Terminology of three-dimensional and four-dimensional ultrasound imaging of the fetal heart and other moving body parts.Ultrasound Obstet Gynecol 2003; 22: 336–344. • 3. Goncalves LF, Lee W, Chaiworapongsa T, Espinoza J,Schoen ML, Falkensammer P, Treadwell M, Romero R. Fourdimensional ultrasonography of the fetal heart with spatiotemporal image correlation. Am J Obstet Gynecol 2003; 189:1792–1802. • 4. Falkensammer P. Spatio-temporal image correlation for volume ultrasound. Studies of the fetal heart. GE Healthcare: Zipf, Austria, 2005. • 5. Goncalves LF, Lee W, Espinoza J, Romero R. Examination of the fetal heart by four-dimensional (4D) ultrasound with spatiotemporal image correlation (STIC). Ultrasound Obstet Gynecol 2006; 27: 336–348.
  • 209. • Three dimensional (3D) ultrasound (USG) and 4D i.e. real • time 3D are a natural development of the imaging technology • and were first demonstrated nearly 15 years ago, but are • becoming a clinical reality only now. Methods for 3D • reconstruction of CT and MRI images have achieved an • advanced state of development. 3D applications in ultrasound • have lagged behind CT and MRI, because ultrasound data is • much more difficult to render in 3D. Only in the past few • years has the computing power of ultrasound equipment • reached a level adequate enough for the complex signal • processing tasks needed to render ultrasound data in three • dimensions. The clinical application of 3D ultrasound is likely • to advance rapidly, as improved 3D rendering technology • becomes more widely available
  • 210. • The advantages of 3D and 4D ultrasound in certain areas are unequivocal. Most centres already apply its use in the workup of fetal anomalies involving the face, limbs,thorax, spine and the central nervous system. The use of this technology in applying color doppler, in guiding needles for different puncture procedures as well in evaluating • the fetal heart are currently under close research scrutiny.
  • 211. • 3D ultrasound helps the bonding between the parents and their future offspring, and consultants understand fetal pathology better and can plan postnatal interventions better. The multiplanar presentation and niche mode are quite useful to determine the extension – inside or outside the organs, of nodules, cysts or tumors. The volume measurement is better assessed with 3D and we can perform studies that follow growth in order to decide medical or surgical treatment. The VOCAL(R) makes it possible to obtain a proper after-treatment follow-up of focal disorders in these small organs. Neovascularization is clearly viewed with 3D USG and probably can suggest malignant origin of a neoplasm. 3D USG offers a more comprehensive image of anatomical structures and pathological conditions and also permits observation of the exact spatial relationships
  • 212. • More studies are needed to demonstrate specificity and sensitivity of 3D and 4D USG. There are limitations to adequate visualization of fetal anatomy with 3D/4D technology. If there is inadequate amniotic fluid surrounding the fetus, or if the fetus has its face in the posterior position in the uterus, there will be difficulty visualizing structures and the face.
  • 213. • 3D allows a simultaneous display of multiple sequential parallel planes of the fetal structures, but there is some uncertainty if an isolated image in one of the multislice images represents the exact level of a fetal structure. Another problem is the creation of false expectations and overall the medical value is limited. Pregnant women will ask for a picture of their fetus like those they have seen in advertisements and put pressure on the scanning centres. Such is the demand in the United States that technician operated 4D ultrasounds are readily available in scanning booths in shopping malls, enabling parents to purchase a video of their moving fetus. This creates problems later on when women, having already had such USG, do not realise that they need a targeted anomaly scan
  • 214. • Endometrial thickness, endometrial pattern, pulsatility index (PI) and resistance index (RI) of uterine vessels, endometrial volume, vascularization index (VI), flow index (FI) and vascularization flow index (VFI) of endometrial and subendometrial regions have been studied by 3D with power dopplers on the day of oocyte retrieval in patients undergoing the first IVF cycle. Uterine RI, endometrial VI and VFI were significantly lower in the pregnant group than in the nonpregnant group. There was a nonsignificant trend of higher implantation and pregnancy rates in patients with absent endometrial or subendometrial blood flow. The number of embryos replaced and endometrial VI were the only two predictive factors for pregnancy.
  • 215. • Endometrial and subendometrial blood flows measured by 3D power Doppler ultrasound were not good predictors of pregnancy if they were measured at one time-point during IVF treatment. A similar study noted that endometrial volume decreased significantly after hCG injection in women who conceived, but not in those who did not.
  • 216. • Along with crown-rump length (CRL), the size (diameter) of embryonic structures such as gestational sac (GS) and yolk sac (YS) may have prognostic value for embryonic development. First trimester volume calculations of these structures using transvaginal 3D USG technic have been done. Volumetry of GS proved to be a sensitive predictor for pregnancy outcome and can be a good supplement to CRL measurements. However, no statistically significant difference was found when YS volumes of normal and abnormal pregnancies were compared. Specificity, sensitivity, positive and negative predictive values of GS volumes and CRL were similar. Mean YS/GS ratios also had good predictive values (P <0.05)
  • 217. • 4D was successfully used to perform amniocentesis, CVS,cordocentesis, and intrauterine transfusion. Using 4D USG guidance, most procedures were performed within 5 minutes and with a 100% success rate, even in cases involving severe oligohydramnios, thin placenta and narrow umbilical veins. Moreover, there were no serious complications during or after any procedure. This appeared to contribute to the accuracy of needle placement by eliminating the lateralization phenomenon when a fixed needle guide attachment was used. • Needle tip visualization was seen in each orthogonal plane inmost freehand 4D amniocentesis cases
  • 218. • Presently, both 2D and 4D methods are required for the assessment of early fetal motor development and motor behavior. Several movement patterns, such as sideway bending, hiccup, breathing movements, mouth opening and facial movements could be observed only by 2D USG .Isolated hand movement and subtypes of hand movements were easily recognized by 4D USG. • All subtypes of hand to head movement can be seen from 13 weeks of gestation with fluctuating incidence. Facial activities and different forms of expression are easily recognized. 4D USG is superior over real time 2D USG for qualitative, but inferior for quantitative analysis of hand movements. 4D USG makes it possible to determine the exact direction of the fetal hand, but the exact number of each type of hand movements can still not be determined.4D USG is superior to 2D USG in the evaluation of complex facial activity and expression.
  • 219. Among facial activities observed by 4D USG, simultaneous eyelid and mouth movements dominate between 30 and 33 weeks of gestation. Pure mouth movements such as mouth opening, tongue expulsion, yawning and pouting are present, but at a significantly lower incidence. Facial expressions such as smiling and scowling can be precisely observed using 4DUSG 12. There were no movements observed in fetal life that were not present in neonatal life; the Moro reflex was present only in neonates
  • 220. • Inclusion of 3D and 4D ultrasound imaging in the examination of cleft lip and/or palate, allows easier and more rapid screening and more precise evaluation of the different cleft constituents . 3D USG can be a reliable technic for visualizing most fetal cranial sutures and fontanels. By performing a sagittal and a transverse scan, most of the sutures and fontanels can be made visible during the second half of pregnancy. Visualization depends on gestational age Gray-scale and color Doppler dynamic 3D displays and multiplanar views used to assess cardiac gating and cardiac morphology demonstrate clinically useful 4D images of the fetal heart. The reconstruction of 3D and multiplanar views provided additional views not obtainable by 2D imaging
  • 221. • Approximately one third of clinical rectoceles do not show a sonographic defect, and the presence of a defect is associated with age, not parity . While 3D pelvic floor imaging is a field that is still in its infancy, it is already clear that the method has opened up entirely new opportunities for the observation of functional anatomy.
  • 222. • The exact applicability of 3D and 4D USG is yet to be ascertained. The American Institute of Ultrasound in Medicine has convened a panel of physicians and scientists with interest and expertise in 3D USG to discuss the current diagnostic benefits and technical limitations in obstetrics and gynecology and to consider the utility and role of this type of imaging in clinical practice now and in the future
  • 223. References • 1. Lees W. Ultrasound imaging in three and four dimensions. Seminars in Ultrasound, CT & MR. 2001;22:85-105. • 2. Timor-Tritsch IE, Han E, Platt LD. Three-dimensional ultrasound experience in obstetrics. Curr Opin Obstet Gynecol 2002;14:569-75. • 3. Maymon R, Herman A. Ariely S et al. Three-dimensional vaginal sonography in obstetrics and gynaecology. Hum Reprod Update2000; 6:475-84. • 4. Fernandez LJ, Aguilar A, Pardi S. Three-dimensional ultrasound in small parts: Is it just a nice picture? Ultrasound Quarterly2004;20:119- 25. • 5. Leung KY, Ngai CSW, Chan BC et al. Three-dimensional extended imaging: a new display modality for three-dimensional ultrasound examination. Ultrasound Obstet Gynecol. 2005; 26:244-51. • 6. Ng EHY, Chan CCW, Tang OS et al. The role of endometrial and sub endometrial blood flows measured by three-dimensional power Doppler ultrasound in the prediction of pregnancy during IVF treatment. Hum Reprod 2006; 21:164-70.
  • 226. To assist clinicians in assigning gestational age based on ultrasound biometry. • To determine whether ultrasound dating provides more accurate gestational age assessment than menstrual dating with or without the use of ultrasound. • To provide maternity health careproviders and researchers with evidence-based guidelines for the assignment of gestational age. • To determine which ultrasound biometric parameters are superior when gestational age is uncertain. • To determine whether ultrasound gestational age assessment is cost effective.
  • 227. • Accurate assignment of gestational age may reduce post-dates labour induction and may improve obstetric care through allowing the optimal timing of necessary interventions and the avoidance of unnecessary ones. More accurate dating allows for optimal performance of prenatal screening tests for aneuploidy. A national algorithm for the assignment of gestational age may reduce practice variations across Canada for clinicians and researchers. Potential harms include the possible reassignment of dates when significant fetal pathology (such as fetal growth restriction or macrosomia) result in a discrepancy between ultrasound biometric and clinical gestational age. Such reassignment may lead to the omission of appropriate—or the performance of inappropriate—fetal interventions.
  • 228. • 1. When performed with quality and precision, ultrasound alone is more accurate than a “certain” menstrual date for determining gestational age in the first and second trimesters (≤ 23 weeks) in spontaneous conceptions, and it is the best method for estimating the delivery date. • 2. In the absence of better assessment of gestational age, routine ultrasound in the first or second trimester reduces inductions for post-term pregnancies.
  • 229. • 3. Ideally, every pregnant woman should be offered a first-trimester dating ultrasound; however, if the availability of obstetrical ultrasound is limited, it is reasonable to use a second-trimester scan to assess gestational age. • 4. Notwithstanding Summary Statements 1, 2, and 3, women vary greatly in their awareness of their internal functions, including ovulation, and this self-knowledge can sometimes be very accurate.
  • 230. • The accurate dating of pregnancy is critically important for pregnancy management from the first trimester to delivery, and is particularly necessary for determining viability in premature labour and in post-dates deliveries.Prior to the widespread use of ultrasound, caregivers relied on a combination of history and physical examination to clinically determine gestational age. Ultrasound gave clinicians a method to measure the fetus and therefore to estimate gestational age. Much of our current clinical practice is based on studies from the 1980s and 1990s. As new information emerges in fields, such as reproductive biology, perinatal epidemiology, and medical imaging, our current clinical practice is being challenged. “Certain” menstrual dating, for example, is less certain than previously thought.
  • 231. • When ultrasound is performed with quality and precision, there is evidence to suggest that dating a pregnancy using ultrasound measurements is clinically superior to using menstrual dating with or without ultrasound, and this has been advocated and adopted in other jurisdictions.
  • 232. • 1. First-trimester crown-rump length is the best parameter for determining gestational age and should be used whenever appropriate. • 2. If there is more than one first-trimester scan with a mean sac diameter or crown-rump length measurement, the earliest ultrasound with a crown-rump length equivalent to at least 7 weeks (or 10 mm) should be used to determine the gestational age. Recommendations
  • 233. • 3. Between the 12th and 14th weeks, crown-rump length and biparietal diameter are similar in accuracy. It is recommended that crown-rump length be used up to 84 mm, and the biparietal diameter be used for measurements > 84 mm. • 4. Although transvaginal ultrasound may better visualize early embryonic structures than a transabdominal approach, it is not more accurate in determining gestational age. Crown-rump length measurement from either transabdominal or transvaginal ultrasound may be used to determine gestational age.
  • 234. • 5. If a second- or third-trimester scan is used to determine gestational age, a combination of multiple biometric parameters(biparietal diameter, head circumference, abdominal circumference, and femur length) should be used to determine gestational age, rather than a single parameter. • 6. When the assignment of gestational age is based on a third trimester ultrasound, it is difficult to confirm an accurate due date. Follow-up of interval growth is suggested 2 to 3 weeks following the ultrasound.
  • 235. GESTATIONAL AGE ESTIMATES USING CLINICAL DATING • The clinical estimate of gestational age typically relies on clinical history (menstrual cycle length, regularity, and recall of the first day of the last menstrual period), followed by confirmation by physical examination or other signs and symptoms.
  • 236. Dating Based on Menstrual History • Dating by certain menstrual history is inexpensive and • readily available. Typically, the EDD is based on a 280- • day gestation from the first day of the LMP. Certain • menstrual dating criteria assume regular cycles, ovulation • at the midpoint of the cycle, fertilization on the middle • day of the cycle, correct recall of the onset of the LMP, • and the woman having been free of oral contraceptives • for several months prior.
  • 237. • Women vary greatly in their • awareness of their internal functions, including ovulation. • Their self-knowledge of ovulation can sometimes be very • accurate; however, the only truly certain clinical history • is one in which the dates of ovulation, fertilization, • and implantation are precisely known, as in ART, in • which records include the date of oocyte retrieval, and • other methods of timed ovulation and fertilization. • Unfortunately, without timed ovulation and fertilization • as in ART and other timed methods, clinical history is • often not reliable.10 Campbell et al. demonstrated that • 45% of pregnant women are uncertain of menstrual • dates as a result of poor recall, irregular cycles, bleeding • in early pregnancy, or oral contraceptive use within 2 • months of conception
  • 238. • Even if menstrual history is correct, the exact time • of ovulation, fertilization, and implantation cannot be • known. Women may undergo several “waves” of follicular • development during a normal menstrual cycle, which • may mean ovulatory inconsistency during any given • cycle.12,13 Sperm may survive for 5 to 7 days in the female • reproductive tract, a “known” conception date is therefore • not completely reliable.14 Recent studies suggest the • ovulation-to-implantation duration can vary by as much as • 11 days, and this may affect fetal size and growth.15 Even • in women who are certain of menstrual dating, delayed • ovulation is an important cause of perceived prolonged • pregnancy and is more likely to occur than early ovulation.16 • Some authors have suggested that 282 days should be used • instead of 280 to improve dating accuracy, since it is more • likely that women will ovulate later rather than earlier than • predicted.9 All of these factors conspire to make it difficult • to accurately predict gestational age based on menstrual • history.
  • 239. Dating Based on Clinical Examination • The size of the uterus, estimated through pelvic or • abdominal examination, can be roughly correlated with • gestational age; however, factors that affect uterine size • (such as fibroids) and maternal body characteristics (such • as obesity) will affect such an estimate. The uterus is • approximately the size of a grapefruit at 10 to 12 weeks. • At 20 weeks the fundus reaches the umbilicus. After 20 • weeks the symphysis fundal height, in centimetres, should • correlate with the week of gestation.7,17 Fetal heart tones • are audible at 11 to 12 weeks with electronic Doppler • devices, and this audibility can also assist in the clinical • assignment of gestational age.
  • 240. Gestational Age Estimation Based on Ultrasound Findings
  • 241. • Ultrasound biometric measurements determine • gestational age based on the assumption that the size of • the embryo or fetus is consistent with its age. Biological • variation in size is less during the first trimester than in • the third trimester. Ultrasound estimation of gestational • age in the first trimester is therefore more accurate than • later in pregnancy.18 Full descriptions of each parameter • and published ranges of accuracy are outlined in Table 2.
  • 243. • The determination of gestational age in the first trimester • uses the mean gestational sac diameter and/or the crown– • rump length. During the first 3 to 5 menstrual weeks an • intrauterine pregnancy is first signaled by the presence • of a gestational sac.19 The gestational sac represents the • chorionic cavity, and its echogenic rim represents the • implanting chorionic villi and associated decidual tissue.20 • The smallest gestational sac size that can be clearly • distinguished by high frequency transvaginal transducers • is 2 to 3 mm, which corresponds to a gestational age of • about 32 to 33 days.21 The MSD is a commonly used, • standardized, way to estimate gestational age during early • pregnancy. It is less reliable when the MSD exceeds 14 mm • or when the embryo can be identified.22 The growth of • the MSD is approximately 1 mm per day.23 CRL has lower • interobservor variability than MSD, and may thus be better • for dating a pregnancy
  • 244. • Yolk Sac • When the yolk sac appears in the gestational sac it provides • confirmation of an intrauterine pregnancy and may be • initially visible as early as the start of the 5th week or as • late as the 6th week. It grows to a maximal size of 6 mm • by 10 weeks and gradually migrates to the periphery of • the chorionic cavity. At the end of the first trimester it • becomes undetectable. Although the presence of the yolk • sac is helpful in determining the presence of an intrauterine • pregnancy, direct measurement of this structure is not • useful in determining gestational age
  • 245. • Crown-Rump Length • Direct measurement of the CRL provides the most • accurate estimate of gestational age once the embryo is • clearly seen. Ideally, either the best CRL or the average • of several satisfactory measurements should be used.26 • The CRL measurement is reported to be accurate for • dating to within 3 to 8 days.22,27–39 The MSD should not • be used to estimate gestational age once the CRL can be • measured
  • 246. • The narrowest confidence interval appears to be • between 7 and 60 mm for CRL.3,29,30,40 The slope of the • embryonic growth curve is small before this time and it • can be difficult to clearly identify a very early fetus; thus, • it is this committee’s expert opinion that reliability and • measurability is best when the CRL is at least 10 mm. If • more than one scan is performed in the first trimester, the • earliest scan with a CRL of at least 10 mm should be used. • To avoid performing extra ultrasounds, it is acceptable to • time the dating scan to coincide with nuchal translucency • screening (if available). • Several studies have evaluated CRL and BPD between • 12 and 14 weeks, with conflicting results. The majority • suggest there is no clinically important difference among • confidence intervals, suggesting that either CRL or BPD • should be used at this gestational age.41–44 The 84 mm • threshold for CRL for estimating gestational age, as • suggested by the ISUOG, seems reasonable
  • 247. • Recommendations • 1. First-trimester crown-rump length is the • best parameter for determining gestational • age and should be used whenever • appropriate. (I-A) • 2. If there is more than one first-trimester scan • with a mean sac diameter or crown-rump length • measurement, the earliest ultrasound with a crownrump • length equivalent to at least 7 weeks (or • 10 mm) should be used to determine the gestational • age.
  • 248. • 3. Between the 12th and 14th weeks, crown- rump • length and biparietal diameter are similar in accuracy. • It is recommended that crown-rump length be used • up to 84 mm, and the biparietal diameter be used for • measurements > 84 mm.
  • 249. • Recommendation • 4. Although transvaginal ultrasound may better • visualize early embryonic structures than a • transabdominal approach, it is not more accurate • in determining gestational age. Crown-rump length • measurement from either transabdominal or • transvaginal ultrasound may be used to determine • gestational age.
  • 250. Transabdominal Versus Transvaginal Ultrasonography • Transvaginal ultrasound is typically used to evaluate • early first trimester pregnancy structures, such as the • gestational sac, yolk sac, and embryo. Original studies • comparing transabdominal and transvaginal techniques in • early pregnancy demonstrated that TV was the superior • method.45–47 Perhaps because of better technology, more • recent studies have not found the same result. Grisolia • et al. concluded that the accuracy of TV ultrasound • has not been shown to be superior to TA ultrasound in • dating pregnancies.31 Other authors have found that TA is • comparable to TV in determining gestational age if CRL is • measurable after 6 weeks.
  • 251. • Crown-Rump Length in Pregnancies Conceived • by Assisted Reproductive Technology • When the conception date is known absolutely, as with • timed ovulation/fertilization during ART, the EDD • should be calculated based on the fertilization date. • Studies have demonstrated that the CRL measurements • in IVF pregnancies are those to be expected in naturally • conceived pregnancies, suggesting that study results can be • extrapolated between the 2 populations
  • 252. Signs of Fetal Maturity • Identification of certain US findings suggest that a fetus • has reached the third trimester and may correlate with • fetal lung maturity and gestational age. These parameters • are the epiphyseal ossification centres of the distal femur, • proximal tibia, and proximal humerus. The measurement of • these ossification centres does not precisely correlate with • gestational age; however, their presence may be helpful late • in pregnancy when the gestational age is not known. The • presence of distal femoral epiphysis has a PPV of 96% for • indicating a pregnancy of at least 32 weeks, the proximal • tibial epiphysis has a PPV of 83% for indicating a pregnancy • of at least 37 weeks, and the proximal humeral epiphysis • has a PPV of 100% for indicating a pregnancy of at least • 38 weeks
  • 253. WHAT IS THE BEST METHOD FOR ASSIGNING GESTATIONAL AGE? • Currently, most centres in Canada use a combined • approach in which US is used to confirm reliable • menstrual dating. If there is an unreliable menstrual • history, the US prediction of EDD is used. Clinical • judgement is used to resolve conflicting data. However, • centres vary in terms of confidence intervals and • biometry charts used. • Many studies evaluating menstrual dating, compared with • US dating, in the first and second trimesters have found US • dating superior for predicting the actual date of delivery.92–98 • No study has shown that it is inferior to menstrual dating. • Menstrual dating underestimates the US-based EDD by • an average of 2 to 3 days.95 Ultrasound dating alone was • significantly better in predicting the actual date of delivery • than any of the dating policies using menstrual dates alone • or in combination with US
  • 254. • Many studies document that the use of US dates reduces • the rate of post-dates pregnancy by about 70% even in • the face of certain menstrual history.92,96,97,99,100 The most • recent Cochrane systematic review found reduced rates • of induction for post-term pregnancy (OR 0.59; 95% CI • 0.42 to 0.83) among women who underwent routine US • in early pregnancy (< 24 weeks) and concluded that early • pregnancy US enables better gestational age assessment, as • well as conferring other benefits
  • 255. • Using US-based gestational age assignment would also • result in improved performance of prenatal screening • programs. Using US estimates exclusively would increase • sensitivity for Down syndrome anywhere from 9% to 16%, • and/or decrease false-positive rates (for a set sensitivity) • by 2.6%.102,103 There might be a very slight increase in the • screening positive rate for open neural tube defects, but • this is more than offset by the decrease in false-positive • rates for Down syndrome. The common practice of • using certain menstrual dates confirmed by US is inferior • to using US alone.104 In the context of serum screening, • first and early second-trimester US parameters perform • similarly.
  • 256. Important notes • 1. When performed with quality and precision, • ultrasound alone is more accurate than a “certain” • menstrual date for determining gestational age • in the first and second trimesters (≤ 23 weeks) in • spontaneous conceptions, and it is the best method • for estimating the delivery date. (II) • 2. In the absence of better assessment of gestational • age, routine ultrasound in the first or second • trimester reduces inductions for post-term • pregnancies
  • 257. • 3. Ideally, every pregnant woman should be offered • a first trimester dating ultrasound; however, if the • availability of obstetrical ultrasound is limited, it is • reasonable to use a second trimester scan to assess • gestational age. (I) • 4. Notwithstanding Summary Statements 1, 2, and • 3, women vary greatly in their awareness of their • internal functions, including ovulation, and this selfknowledge • can sometimes be very accurate.
  • 258. SHOULD ROUTINE FIRST TRIMESTER DATING ULTRASOUNDS BE OFFERED TO ALL PREGNANT WOMEN?
  • 259. • A routine first trimester US has many advantages: early • identification of gross anomalies and multiple gestations, • more precise dating, improved performance of prenatal • screening, and an opportunity to perform nuchal • translucency as part of prenatal genetic screening. In many • jurisdictions, a dating US is performed routinely in all • women, regardless of menstrual history. The availability, • quality, and health care cost of obstetrical US is a significant • factor in local patterns of practice.2 Crowther et al. found • routine early US (< 17 weeks) provided more precise • estimates of gestational age than later US (18 to 22 weeks), • reduced the need to adjust the EDD in mid-gestation, and • decreased maternal anxiety
  • 260. • The balance of the literature supports using first trimester • US to reduce the incidence of induction for post-dates • pregnancy. Although no comprehensive cost • benefit analysis has been done on routine early US for • dating, the current literature suggests significant benefits • are present. Ideally, where it is readily available, a first • trimester US for dating should be performed. Where • nuchal translucency is available, this scan can serve both • functions. When a first trimester US cannot be obtained, • the available evidence suggests the second trimester US • can be used for similar benefits