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Sample Chapter Differential Diagnosis in Obstetric and Gynaecologic Ultrasound 3e by Bisset To Order Call Sms at +91 8527622422

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  • 1. P A R T I Obstetrics Early Pregnancy, 02 Fetal Well-Being and Growth, 24 Structural Fetal Abnormalities, 78 Fetal Face and Neck, 119 Fetal Thorax, 140 Fetal Echocardiography, 150 Fetal Abdomen and Pelvis, 169 Fetal Genitourinary System, 200 Fetal Musculoskeletal System, 220
  • 2. 2 C H A P T E R 1 Early Pregnancy MENSTRUAL AGE VERSUS GESTATIONAL AGE Menstrual age refers to the first day of the last normal menstrual period preceding pregnancy. The menstrual age is used clinically for dating pregnancy as it is an easily identifiable landmark. Gestational age refers to age from conception and usually lags behind the menstrual age by 2weeks. THE FIRST TRIMESTER The first trimester is defined as the 13weeks fol- lowing the first day of the last menstrual period. The first clue that the patient might be pregnant is the appearance of a small cyst eccentrically located within a single layer of the endome- trium; this is soon followed by the appearance of a double bleb sign, the yolk and then an echo- genic cylinder that is the embryonic pole. There is an echogenic rim around the early GS that is the decidual reaction. The amniotic membrane is seen to surround the early embryo; the YS is out- side the amniotic cavity and is gradually pushed to the periphery as the amniotic cavity expands. These early findings are depicted in Figure 1-1. ROLE OF ULTRASOUND IN THE FIRST TRIMESTER1 • Toidentifysite(s)ofpregnancy,e.g.intrauterine, interstitial or ectopic • To detect early pregnancy failure 1US should not be used solely as a diagnostic test to confirm the presence of uncomplicated pregnancy. • To predict outcome in the presence of a live embryo • To assess gestational age, uncertain dates or LMP discrepancy • To determine the number of embryos and assess chorionicity and amnionicity • To evaluate retained products of conception • To diagnose gestational trophoblastic disease • To diagnose some fetal anomalies With TVS, there is improved detection rate of fetal anomaly in the first trimester. However, caution is needed in interpreting certain findings in the first trimester such as cystic hygroma, choroid plexus cysts, pyelactasis and echogenic bowel, which may resolve spontaneously. A significant false-negative rate for fetal anomaly has also been recorded in the first trimester of pregnancy. • To assess associated maternal abnormalities, e.g. ovarian cysts, uterine leiomyomas and retained IUCD • US-guided chorionic villus sampling • To assess therapeutic abortion PREDICTORS OF EARLY PREGNANCY FAILURE Pregnancy failure in the first trimester is a com- mon problem, as approximately a quarter of pregnancies fail during this period. Lack of Cardiac Activity Absent cardiac activity is taken to indicate death but it should be remembered that in very small
  • 3. A B C D E F G H FIGURE 1-1 Ultrasound features of early pregnancy. The earliest evidence of an IUP is the appearance of the GS, seen as a small cyst in a single layer of the endometrium (A); soon a tiny two-compartment bleb appears inside (B); this is the double bleb sign. Occasionally, a small amount of fluid might be seen outside the GS; this early bleed might not be significant but does warrant a follow-up for confirming viability (C). By about 5–6weeks, a small well-defined internal cyst, the YS, and a tiny bar of tissue, the embryonic pole, appear in the GS (D); at this time, embryonic cardiac flicker might also become apparent. An early sign of healthy pregnancy is the echogenic rim that is the decidualized endometrium (E); the absence of this echogenic rim should raise concern of an abnormal pregnancy (F, a blighted ovum). The YS, vitelline duct and amni- otic membranes become evident as well as a recognizable embryo with a large head and small limb buds (G, H); the YS is outside the amniotic membrane and as the amniotic cavity forms and expands, this is pushed by the amnion against the chorion; this is seen very well in image H. (Image H, courtesy of Dr Allen G. Worral, USA.)
  • 4. CHAPTER 1 Early Pregnancy4 embryos (<4mm) cardiac flicker might not be appreciated and ultrasound should be repeated after a few (2–3) days to confirm this impression. An embryonic length of 5mm is a threshold value in ultrasound at which cardiac activity should be visible in all cases (Figure 1-2J, O–Q). Yolk Sac Characteristics The YS functions as a haematopoietic organ and facilitates nutrition transfer in early pregnancy gestation. An abnormal Yolk Sac is associated with embryonic death and poor pregnancy out- come. Absence of a YS on TVS when GS size is 8mm or more is said to be 100% sensitive for anembryonic gestation but has a 9% specificity and a positive predictive value of 65%. Out of these, 22% subsequently develop a viable preg- nancy. However, the presence or absence of a YS cannot be used to determine if a pregnancy is normal when the GS is smaller than 18mm. Cal- cification is associated with a poor prognosis. An abnormally shaped YS and lack of growth of the YS are further signs of pregnancy failure. Unusu- ally large or small YS (Figure 1-2C–F) has been associated with embryonic death. Nevertheless, transient abnormalities of YS shape may some- times occur in normal pregnancies. Gestational Sac Features Just like embryonic length threshold values, there are values for other structures that help in deciding whether to wait or diagnose abnor- mality. On TVS, an MSD of ≥18 mm should always have a visible YS, and a mean sac diam- eter of >20 mm should always have a visible embryo. If the sac diameter has not reached the threshold value, it would be prudent to wait a few days; if the sac diameter exceeds threshold values without the associated find- ings, an abnormal pregnancy can be diagnosed (Figure 1-2A and B). An irregular GS, thin or absent echogenic endo- metrium (<2mm) around it (decidual reaction), absent double decidual line sign are portends of poor outcome. Small Sac Size: Discordance between MSD and CRL There is a large range of normal GS size. The peak average difference between MSD and CRL is 14.4mm at 8week menstrual age, which progressively diminishes to less than 1mm by 12weeks menstrual age. Close follow-up is nec- essary with borderline findings as patients can go on to develop a normal pregnancy. Abnormal Amnion A collapsing amnion, an amnion with irregular margins and an amnion with no visible embryo indicate pregnancy failure. An enlarged amni- otic cavity or a YS diameter more than 2 standard deviations above the mean when compared with mean GS diameter is associ- ated with poor outcome. A small amniotic cav- ity with early oligohydramnios is a worrying sign but should be diagnosed only when the threshold of MSD-CRL <4 mm is crossed (Fig- ure 1-2L and M). FIRST TRIMESTER ANATOMY THAT MAY MIMIC FETAL ANOMALY Fetal Rhombencephalon The rhomboid fossa of the normally developing rhombencephalon can appear as a small (3–4mm) ‘cystic’ structure in the posterior aspect of the cranium, between 8 and 10weeks menstrual age (Figure 1-3C). It should not be confused with Dandy-Walker malformation, a cystic posterior fossa abnormality. See image: Fig 3-15, page 112. Telencephalic and Mesencephalic Vesicles The brain develops from the cranial part of the neural tube. During the fourth week, the fore- brain (prosencephalon), midbrain (mesencepha- lon) and the hindbrain (rhombencephalon) form as primary vesicles. During the fifth week, the forebrain divides into the telencephalon and
  • 5. 5CHAPTER 1 Early Pregnancy A B C D E F FIGURE 1-2 Ultrasound features in early failed pregnancy. (A, B) A large GS (18–20m) without YS or embryonic pole and a poor echogenic rim is a feature of early anembryonic pregnancy (blighted ovum). An abnormally large YS (>7mm) is often associated with an abnormal outcome and in both cases (C, D) pregnancy failed to progress. Small echogenic YSs (E, F, arrows) are also associated with poor outcome in many cases but a close follow-up in all cases of abnormal YS size is recommended because a few can go on to normal pregnancy. Continued
  • 6. CHAPTER 1 Early Pregnancy6 G H I K J FIGURE 1-2, cont’d Subchorionic haemorrhage, white arrow, (G–I) can range from an extensive collection almost all around the GS (G) to a collection at one end (I); if the collection surrounds more than half the diameter of the sac or extends behind the placental implantation site the prognosis is worse but follow-up should be done as the outcome is unpredictable and many early pregnancies with early ominous looking collections go on to progress and many pregnancies with relatively trivial collec- tions fail to thrive. Cardiac flicker should be visible from very early on and in this 8 weeks pregnancy (J) with recent slight bleed- ing it was not demonstrable; this is a black and white rendition of a Doppler image showing lack of cardiac activity and flow. This was a case of missed abortion. The patient in image (K) had a history of recent bleeding and on ultrasound a distorted compressed GS was noted low down in the region of the body; this was an abortion in progress and the sac was expelled within the next few hours, with no sac visible on a follow-up ultrasound after 24h.
  • 7. 7CHAPTER 1 Early Pregnancy L M N O P Q FIGURE 1-2, cont’d First trimester oligohydramnios, diagnosed when the sac is tight around the embryo has a generally poor prognosis but caution must be used when diagnosing this. In some normal pregnancies (L) the MSD-CRL value falls below 10mm. The threshold for diagnosing first trimester oligohydramnios is ≤4mm; image M shows a 12-week fetus with a large abdominal cyst and complete anhydramnios with no measurable pocket amniotic fluid seen. (N) Eight weeks missed abortion with oligohydramnios. (O) Relatively normal looking embryo with absent cardiac activity; there is a large extra-amniotic space (arrow). (P, Q) Distorted featureless embryo with absent cardiac activity and a large sac. (Image N, courtesy of Dr Jaydeep Gandhi, India; image Q, courtesy of Dr Gunjan Puri, India.)
  • 8. CHAPTER 1 Early Pregnancy8 diencephalon and the hindbrain divides partially into the metencephalon and myelencephalon. The telencephalic and mesencephalic vesicles appear at about 7weeks gestation and can be detected prenatally. Physiologic Gut Herniation This appears at about 8weeks and may persist until 12weeks in 20% of normal fetuses. The umbilical cord may be the site of cysts, varying from 2 to 7mm, in under 1% of normal pregnan- cies (Figure 1-3A). TRANSIENT FIRST TRIMESTER FETAL ANOMALIES With TVS, there is improved detection rate of fetal anomalies in the first trimester. Caution is needed in interpreting certain findings (vide infra). Increased Nuchal Translucency Increased first trimester nuchal oedema/translu- cency (NT) may be a transient phenomenon. How- ever, persisting nuchal oedema may need close follow-up as it is an important ultrasonographic A B C FIGURE 1-3 Normal first trimester structures that can mimic fetal anomalies. (A) Physiological gut herniation (white arrow); this is seen as an echogenic nodule projecting out of the abdominal wall, longitudinal section on the right and transverse section on the left. (B) Limb buds (open arrows) that can appear as small echogenic nodules on the ventral surface of the body. (C) Rhombencephalon appearing as a prominent cyst in the fetal brain (dashed arrow).
  • 9. 9CHAPTER 1 Early Pregnancy marker of fetal chromosomal abnormality. NT in the first trimester is associated with aneuploidy particularly trisomy 13, 18 and 21. An increased NT at 11–14weeks gestational age is a common finding in Down syndrome. NT is normally less than 2.5mm; an increased measurement greater than 2.5mm may indicate the presence of Down syndrome or other chromosomal anomaly (Figure 1-4A–E). The presence of normal karyotype in the presence of increased NT is a strong indication for detailed ultrasound examination for nonkaryo- type defects such as Noonan syndrome, Joubert syndrome and congenital heart defects. The pres- ence of an isolated increased NT is associated with 12.5% prevalence of chromosomal aberrations. Very detailed protocols are available on how to acquire accurate and reproducible NT mea- surement (Box 1-1). Nuchal Cystic Hygroma One review of 72 fetuses with cystic hygroma diag- nosed at 10–14weeks gestation found the mean size of 7.9mm. Just over half had chromosomal abnormalities of which the majority had Down syndrome. The outcome of pregnancy is usually unfavourable (miscarriage, elective termination, and serious structural abnormalities). The overall prognosis of fetal cystic hygroma (Figure 1-4F) detected during the first trimester is poor, and thus sonographic evaluation of fetal nuchal translu- cency thickness in the first trimester is crucial. Axillary Cystic Hygroma Sonographic diagnosis of fetal axillary cystic hygroma has been reported rarely, usually late in gestation. Axillary hygromas are usually small, transient, nonloculated cysts. Some are associ- ated with chromosomal abnormalities. An asso- ciation has been reported with trisomy 21 and 18. Early fetal axillary cystic hygromas are usu- ally different from postnatal axillary cysts in terms of prevalence, structure, and appearance. It also may be a normal variant in the develop- ment of the fetal lymphatic system. Choroid Plexus Cysts This is found in 3.6% normal fetuses; investiga- tors are divided on the question of amniocentesis in isolated CPC but most agree that the presence of additional US abnormalities is an indication for amniocentesis. Abnormal karyotype is found in 1–2.4% of fetuses with isolated CPC. Hydronephrosis Isolated mild pyelactasis (<3/4mm) without progressive change is not associated with sig- nificant pathology and is found in 3.2% of fetuses. Mild pyelactasis is characterized by a small amount of fluid in the renal pelvis and is affected by maternal hydration. However, mild pyelactasis may be a sign of early pathological state. The appropriate threshold for initiating further investigation particularly in the first trimester is controversial but a close watch is essential. Pericardial Effusion Generally when a fetal pericardial effusion is observed it is along one portion of the ventricle or near an atrioventricular valve, but does not surround the heart. A pericardial effusion sur- rounding the heart is considered abnormal even when small. Pleural Effusion Pleural effusion is considered abnormal at any gestational age and even when transient the fetus needs to be evaluated for chromosomal abnor- mality, Turner syndrome, immune hydrops feta- lis, cardiac abnormalities, diaphragmatic hernia, lymphangiectasia and intrauterine infections. Sonographic appearances are those of anechoic fluid collection that conform to fetal chest associ- ated with flattening/inversion of the diaphragm and bulging of the thoracic wall. Chylous effu- sions are indistinguishable from serous pleural effusion in the fetus.
  • 10. CHAPTER 1 Early Pregnancy10 C D E F BBBAA FIGURE 1-4 Nuchal translucency; normal measurement (A, B), increased NT (C, D), markedly increased (E); in this patient, the oedema is generalized and is all around the body (space suit appearance). There is posterior cystic hygroma forma- tion in (F); this has a very high association with aneuploidy, especially Turner syndrome. (Images B, D, and E, courtesy of Dr Allan J. Worral, USA; image F, courtesy of Dr Latha Nataranjan, India.)
  • 11. 11CHAPTER 1 Early Pregnancy Echogenic Bowel Fetal echogenic bowel should be investigated and followed up carefully as it is considered as one of the soft markers for aneuploidy, IUGR, infec- tions and cystic fibrosis. INTRAUTERINE FLUID COLLECTIONS THAT MAY MIMIC A GS A variety of conditions causing fluid collections within the uterine cavity may, in the appropri- ate clinical setting, mimic a GS. Intrauterine fluid collections lack the double ring margin of an IUP and in many of the causes listed below will lack a trophoblastic reaction. • Endometrial bleeding • Retained products of conception • Incomplete abortion • Pseudogestational sac of EP • Endometrial carcinoma • Cervical stenosis/cervical obstruction due to a carcinoma or previous surgery • Endometritis • Endometrial arterial aneurysm – this life- threatening condition has been reported only once; on close inspection it was found to be pulsatile on US, while a duplex arterial wave- form was detected. EMPTY GS A GS is classified as empty when no fetal parts are identified on abdominal scanning in a sac that exceeds 30mm in diameter or with no YS in a sac that exceeds 20mm in diameter. Most • The gestational period must be 11–13weeks and 6days. • The fetal CRL should be between 45 and 84mm. • The magnification of the image should be such that the fetal head and thorax occupy the whole screen. • A mid-sagittal view of the face should be obtained.This is defined by the presence of the echogenic tip of the nose and rectangular shape of the palate anteriorly, the translu- cent diencephalon in the centre and the nuchal membrane posteriorly. Minor deviations from the exact midline plane would cause nonvisualization of the tip of the nose and visibility of the zygomatic process of the maxilla. • The fetus should be in a neutral position, with the head in line with the spine. When the fetal neck is hyperex- tended the measurement can be falsely increased and when the neck is flexed, the measurement can be falsely decreased. • Care must be taken to distinguish between fetal skin and amnion. • The widest part of the translucency must always be measured. • Measurements should be taken with the inner border of the horizontal line of the callipers placed on the line that defines the nuchal translucency thickness – the crossbar of the calliper should be such that it is hardly visible as it merges with the white line of the border, not in the nuchal fluid. • In magnifying the image (pre- or postfreeze zoom), it is important to turn the gain down.This avoids the mistake of placing the calliper on the fuzzy edge of the line which causes an underestimate of the nuchal measurement. • During the scan more than one measurement must be taken and the maximum one that meets all the above criteria should be recorded in the database. • A new approach for the measurement of NT which improves the accuracy of measurements, is with the use of a semiautomated technique. The operator places a box in the nuchal area and the machine automatically selects the best measurement, which uses an algorithm that draws a line through the centre of the nuchal mem- brane and another line at the edge of the soft tissue overlying the cervical spine. The measurement obtained by this method is similar to that obtained manually and it is therefore applicable to the software of the Fetal Medicine Foundation. • The umbilical cord may be round the fetal neck in about 5% of cases and this finding may produce a falsely increased NT. In such cases, the measurements of NT above and below the cord are different and, in the calcu- lation of risk, it is more appropriate to use the average of the two measurements. BOX 1-1 Protocol for Measurement of Nuchal Translucency Reproduced with permission from Fetal Medicine Foundation.Available at www.fetalmedicine.com.
  • 12. CHAPTER 1 Early Pregnancy12 empty sacs are abnormal in shape (Figures 1-1F and 1-2A and B). Normal IUP 5–7weeks menstrual age This is less likely with TVS as GS is seen as early as 32days and is seen in all pregnancies with hCG levels of 1000mIU/mL Blighted ovum This term applies to arrested development of a fertilized ovum. Most blighted ova are of an abnormal karyotype Pseudogestational sac of EP The double decidual sign is absent in a pseudogesta- tional sac POSITIVE βhCG WITHOUT IUP Human chorionic gonadotropin (hCG) is a glyco- protein hormone produced by trophoblastic tissues. As trophoblastic tissue is an essential part of preg- nancy; identification of hCG is frequently sought to confirm the presence of pregnancy. However, a false-positive hCG assay may arise in conditions other than pregnancy as hCG may be elaborated by the pituitary, exogenous sources, and both tro- phoblastic and nontrophoblastic neoplasia, result- ing in false-positive laboratory assays for hCG. • Early IUP <5weeks gestation • Recent complete or incomplete abortion • EP • βhCG-producing ovarian tumour – germ cell tumour, primary ovarian choriocarcinoma • Theca lutein cyst associated with pharmaco- logical stimulation with βhCG • Exogenous administration of hCG: hCG is used by some as an aid in weight loss by intra- muscular or oral administration. Following cessation of hCG therapy for 24h the hCG assay usually turns negative on a repeat assay. • Pituitary hCG: Stimulated by gonadotropin- releasing hormone; suppressed by gonadotro- pin-releasing hormone agonist and oestrogen/ progestin therapy. Can also be detected in postmenopausal women due to increased GnRH secretion. • Trophoblastic neoplasm: Consists of pregnancy, gestational trophoblastic neoplasia, and pla- cental site trophoblastic tumours. ULTRASOUND FEATURES OF EARLY IUP Gestation Sac A GS is surrounded by an echogenic asymmet- rical ring that should be visible at 5weeksMA on transabdominal US scan, while on TVS a GS is seen at 32days. A normal sac growth is 0.7– 1.75mm/day (mean=1.33) from 5 to 11weeks. In patients with early pregnancy with a question- able GS a 10MHz intravaginal probe improves the diagnostic confidence. Double Decidual Sac A DDS is useful at 4–6weeks gestational age; it consists of two concentric rings of tissue sur- rounding a portion of an intrauterine GS. The sign develops as a result of protrusion of the GS into the uterus. Yolk Sac At 6weeksMA, a YS and amnion should be visible on transabdominal US. On TVS, a YS is seen in every pregnancy between 36 and 40days; the GS is between 6 and 9mm. YS is seen in 100% normal pregnancies with βhCG level of 7200mIU/mL. Intradecidual Sign This is when the GS is not sufficiently large to impress, protrude into or deform the uterine cen- tral echo complex yet is completely embedded within the decidua. This sign precedes the double decidual sign. This sign does not appear to be sensitive or specific in the diagnosis of IUP. Embryo with Heartbeat Embryo with a heartbeat is expected in all preg- nancies >40days and a GS >9mm on TVS.
  • 13. 13CHAPTER 1 Early Pregnancy RISK GROUPS FOR EP EP rates have increased steadily from 4.5 per 1000 pregnancies in 1970 to 16.8 per 1000 preg- nancies in 1987. All women of reproductive age are at risk of EP. Higher Risk Groups: EP • Delayed transit of zygote ø Previous tubal pregnancy (10-fold increase) ø Previous tubal surgery ø Previous salpingitis particularly chlamydia ø Infertility – shared tubal abnormalities with EP • Infertility ø Ovulation induction ø In vitro Fertilization multiple pregnancy contributory factor ø Gamete intrafollicular transfer – contributory factors include the hydrostatic forces gener- ated during transfer ø Intrauterine contraceptive devices ø History of PID ø Increasing maternal age and parity ULTRASOUND FINDINGS IN EP EP is not always easy to diagnose; the classic triad of missed period, pain and abnormal vaginal bleeding is frequently absent and adnexal mass or cervical tenderness cannot be demonstrated in many patients. Correlation with ultrasound and serum βhCG help in making the correct diagnosis in many patients. Ultrasound is fairly conclusive in the follow- ing situations. • The demonstration of a live pregnancy out- side the uterus. With cardiac flicker and/or the conclusive demonstration of a YS. • The demonstration of a thick ring-like struc- ture with an echogenic rim and an extra- ovarian location is fairly specific. Beware of the corpus luteum that can mimic an ectopic, but the corpus luteum is ovarian in location while an EP is almost always extraovarian. • The demonstration of a live IUP excludes most cases of ectopic pregnancy, although a con- current ectopic and IUP can still be possible (heterotopic pregnancy); this situation is more likely to be met in patients undergoing infertil- ity treatment. The presence of a complex adnexal mass, absent IUP and rising serum βhCG levels make the diag- nosis of EP likely. Free peritoneal fluid, especially if complex and associated with an adnexal nonovarian mass, increases the likelihood of an EP. The likelihood increases if the amount of fluid is large (reaches upper abdomen). US is more sensitive than culdocentesis in detecting haemoperitoneum. The presence of echogenic fluid, which correlates with haemo- peritoneum, is highly suggestive of EP espe- cially when a large quantity of echogenic fluid is detected in the presence of an adnexal mass. Pseudogestational Sac This refers to the collection of a small amount of fluid within the decidualized endometrial canal. This is differentiated from a true GS by its cen- tral location (true sac is in one layer of the endo- metrium) and fusiform or tear drop shape with an inferiorly pointing beak (true sac is usually rounded). A pseudosac will not show a double- line sign, YS or an embryonic pole. Tubal Ring This refers to a thick-walled cystic structure in the adnexa quite separate from the uterus and ovary and is considered a reliable sign of EP. The tubal ring can mimic a corpus luteum cyst when the ovary is not well seen. A corpus luteum cyst is usually thinner, contains clear fluid and appears less echogenic than the endo- metrium. Confusion with a haemorrhagic ovar- ian cyst may arise when surrounding fluid is seen.
  • 14. CHAPTER 1 Early Pregnancy14 Quantitative βhCG An empty uterus in an at-risk woman in associa- tion with a hCG greater than 1800IU/L is highly suggestive of the presence of EP. This level of hCG is highly suggestive of EP but is not diag- nostic. It is reasonable to closely follow up rather than treat early stable cases of EP. Other Biochemical Aids to US Diagnosis Progesterone is produced by the corpus luteum during the early second trimester, until the placenta takes over production of progesterone. A serum progesterone of <5ng/mL is 99.8% predictive of a nonviable pregnancy either EP or IUP. Progester- one levels measuring at least 25ng/mL excludes 97.5% of EPs. The levels of progesterone are independent of gestational age so that a single test can be diag- nostic without the need for serial examinations. Endometrial Thickness 0.5–1.7cm Endometrial changes in the form of a decidual cast occur in 50% of patients and may be indis- tinguishable from IUP. There is no significant dif- ference in endometrial thickness between women with EP and those with spontaneous abortion. A thin endometrium seen on TVS cannot be used to exclude the diagnosis of EP. Doppler Sonography in EP High-velocity and low-impedance flow is seen in both IUP and EP. Colour Doppler often shows a complete or partial ‘ring of fire’ sign in an adnexal mass; this has a low-resistance, high- diastolic component on spectral Doppler. Cor- pus luteum has similar flow characteristics but this is intraovarian in location while an ectopic is almost always extraovarian. Spontaneous Resolution of EP In some patients, an EP resolves spontaneously but the exact incidence is unknown. The features of EP are depicted in Figure 1-5. Endometrial Three-Layer Pattern A well-defined spherical structure forming three hyperechoic layers separated by two hypoechoic layers within the endometrium have been described with EP. However, this sign is con- troversial and has been described in a variety of conditions besides being a normal appear- ance too. The differential diagnosis of the sign includes early IUP and successful implantation in women undergoing in vitro fertilization. It has also been described with trophoblastic regres- sion: symptomatic pregnant patients, clinically stable, serum levels of βhCG levels below a dis- criminatory zone, who lack US evidence of either EP or IUP and when symptoms and serological evidence of pregnancy resolve spontaneously. DIFFERENTIAL DIAGNOSIS OF EP • Any adnexal mass • All causes of fluid in the cul-de-sac • Corpus luteum cysts with/without septa • Torsion of ovarian cyst/neoplasm • Endometriosis • Tubo-ovarian abscess • Torsion/degeneration of a fibroid • Ovarian neoplasm • Haemorrhagic ovarian cyst • Uterine leiomyoma • Haemorrhagic subserosal fibroid • Appendix abscess • Diverticular abscess ULTRASOUND PARAMETERS FOR MEASUREMENT OF GESTATIONAL AGE Post-LMP Approximate Age (Weeks) 5–6 GS volume 7–12 CRL 12–15 BPD, FL, head circumference 24 After 24weeks, there is variation in the rate of growth depending upon genetic and environmental factors and ultrasound dating becomes progressively less accurate
  • 15. 15CHAPTER 1 Early Pregnancy A B E F G H DC FIGURE 1-5 Spectrum of ultrasound findings in EP. The most suggestive finding is of a thick-walled echogenic ring-like structure that is extraovarian (A, B). On Doppler, there is often a hypervascular area surrounding this, the ‘ring of fire’ sign (C); a YS and an embryo can sometimes be recognizable confirming the diagnosis (D) and a cardiac flicker can be picked up (E). Beware of a small collection in the endometrial canal that can mimic an intrauterine GS (F); in fact, this is called the pseudosac of EP. The ectopic can lead to bleeding into the peritoneum and a complex ascites ensues, and echogenic specks, septations and clumps in the ascetic fluid can form (G, H). The white arrow in all images points to the ring-like structure representing the ectopic GS.
  • 16. CHAPTER 1 Early Pregnancy16 GS Size GS can be visualized from 4weeks on TVS and a week later on transabdominal scans. The sac is rarely spherical, so a single diameter is likely to be inaccurate and the average of the three diam- eters (AP, transverse and craniocaudal) is used. The inner-to-inner border is used to read off the sac size against standard charts. Crown–Rump Length This is the most accurate means of dating a preg- nancy. Fetal attitude, especially considerable flex- ion can reduce the reading and the examiner should wait for a more neutral fetal spine curvature before making the measurement. CRL is not affected by most environmental and racial factors. Biparietal Diameter This is generally used in the second and third trimes- ters; the accuracy decreases as pregnancy advances. Femur Length The FL may be measured from 12weeks onwards. It compliments BPD measurement and should be used in all cases. In fact, any long bone can be measured but the FL is easiest to identify and measure, making it the most popular long bone. OTHER FETAL MEASUREMENTS Abdominal Circumference This is a bit more difficult to measure than the BPD or FL but is useful in assessing the weight of the baby, growth appropriateness or dispar- ity between fetal parameters, IUGR, over growth conditions, etc. Head Circumference This is a very useful measurement especially when the fetal head shape exhibits undue narrowing (dolichocephaly) or undue broadening; both conditions are normal variants but can lead to a misleadingly small or large BPD. Fetal Weight Analysis of fetal weight may be performed using standard fetal measurements (AC, HC, FL, BPD, etc.), either singly or in combination. Adding parameters increases accuracy slightly but fetal weight measurement tends to be accurate only within ±10% at best. Fetal Foot Length There are limitations to the use of fetal foot length for gestation age assessment particularly in fetuses with growth abnormalities. The Transverse Cerebellar Diameter The transverse cerebellar diameter (TCD) is con- sidered as a reliable parameter for estimating the duration of gestation. In IUGR, restriction of the cerebellum is usually spared, making TCD a reli- able indicator of gestational age even when other parameters fall off the appropriate growth curve. Throughout pregnancy, TCD measurements allow for the estimation of gestational age that is independent of the shape of the fetal head and offers potential for evaluation of abnormal fetal growth and anomalous development of the central nervous system. CAUSES OF INACCURACY IN ESTIMATING GESTATIONAL AGE FROM MENSTRUAL HISTORY • LMP date not accurately known • Cycle is irregular • Cycle is not 28days long • Bleeding in early pregnancy may mimic a men- strual period • Contraceptive pill recently used as a form of contraception • Postdelivery breast feeding
  • 17. 17CHAPTER 1 Early Pregnancy ADVANTAGES OF ULTRASOUND ESTIMATION OF GESTATIONAL AGE • Allows planning for delivery, including deci- sions for induction of labour and efforts at prolonging pregnancy in cases where the appro- priate period has been exceeded or not reached. • Is vital for the correct interpretation of screen- ing blood tests such as the triple or quad screen for Down syndrome and other conditions. • Is imperative for diagnosing fetal growth abnormalities. CORPUS LUTEUM IN EARLY PREGNANCY The corpus luteum (CL) is identified in the first tri- mester on TVS in most pregnancies. This physiolog- ical structure produces progesterone, which sustains pregnancy until the placenta is formed. At around 7weeks gestation, the functioning CL is no longer necessary because the placenta assumes hormonal function. Consequently, it decreases in size during 8–16weeks gestation and is subsequently main- tained passively for the rest of the term of pregnancy: • Varied US appearances with a mean diameter of 1.9±0.6cm (range 0.8–5.5cm) • Hypoechoic – 34% • Cystic with thick circumferential wall and anechoic centre – 27% • Cystwithscatteredechoesorinternaldebris–23% • Thin-walled simple cyst – 15% • No CL identified – 2% • Circumferential flow partial or all CL on colour flow Doppler – 92% • Flow on pulsed Doppler in 92% with a mean resistive index of 0.49±0.08 (range 0.29–0.91) THE CERVIX IN PREGNANCY Normal Cervix in Pregnancy It is usually difficult to distinguish the cervix from the lower uterine segment in the nongravid state and the first trimester. From midtrimes- ter onwards, the amniotic sac clearly defines the internal os. US has advantages over digital examination; the internal os can be visualized by sonography and hence early changes of cer- vical incompetence can be detected; moreover, there is a decreased risk of infection and cervical irritation. Cervical Length Cervical length is the distance between the internal and external os. The first trimester cervical length is >5 cm. The cervical length decreases to <34 mm at 28 weeks gestation. In patients with multiple gestation, there is sig- nificantly shorter cervical length. Normograms have been developed for twins and triplets that help to identify patients at high risk for pre- term labour. Preterm Labour There is an inverse relationship between US cervical length and the risk of preterm labour. Length <25mm at 24weeks' gestation indicates a fourfold increased risk of preterm labour. Fun- nelling/wedging of the internal os with prolapse of fetal membrane is indicative of the onset of preterm labour. Funnelling of over 60% of the length of the cervical canal is also associated with preterm labour. Incompetent Cervix Cervical incompetence is defined as cervi- cal dilatation without uterine contractions. In patients with a history of pregnancy loss, it is prudent to establish a baseline cervical length measurement before the gestation age when the previous loss occurred with follow-up scans 1–2 weeks depending upon the findings or recent examination or symptoms. TVS com- bined with transfundal pressure or scanning patient in a standing position can illicit early changes.
  • 18. CHAPTER 1 Early Pregnancy18 Dynamic Changing Cervix This dramatic event can be seen during US exam- ination. The cervix shows dynamic changes with varying degree of funnelling of the internal os associated with vigorous closing and opening of the cervix. These changes occur in the absence of uterine contractions. Although most patients with a spontaneously changing cervix deliver preterm, it is not a sign of imminent delivery and with conservative management delivery may be delayed in some. Cervical Cerclage Sonographic guidance can be used to assist place- ment of cervical cerclage as a prophylaxis to pre- term labour in cervical incompetence. Following placement of cervical cerclage, measurements of the canal are made from the internal os to the level of cerclage. Shortening of the upper cervical length <1cm is associated with preterm delivery. The Cervix at Term Several studies using US to evaluate the ripeness and inducibility of cervix have been published and a scoring system has been proposed. Param- eters such as cervical length, cervical diameter and the appearance of the internal os are scored. Using these indices it has been shown that the presence of funnelling and a short cervical length is associated with a shorter duration of induced labour. US has been shown to correlate well with digital examination; however, the firmness of the cervix, which is an important sign of the ripeness of the cervix can only be assessed digi- tally. US technique is useful in patients in whom digital examination is contraindicated such as in patients with premature rupture of membranes and unexplained vaginal bleeding. FALSE-POSITIVE FINDINGS OF INCOMPETENT CERVIX • Uterine contraction – differentiation by the observation of a thickened myometrium associated with uterine contractions, palpa- tion of the uterus, placement of tocodyna- mometer and questioning the patient may disclose the presence of uterine contractions • Narrowed lower uterine segment can mimic funnelling – clarified by observing the cervix over time • Overdistended urinary bladder impression on the lower uterine segment may produce the impression of funnelling of the cervix • Cystic lesions such as nabothian cysts and vaginal cyst can mimic a dilated internal os INCOMPETENT CERVIX: RISK FACTORS • DES exposure in utero associated with cervical hypoplasia • Previous cone biopsy of the cervix • Prior cervical laceration • Prior cervical trauma – cauterization, dilatation, curettage etc. • Ostrogen therapy ABORTION There is 10–25% pregnancy loss rate of all clini- cally diagnosed pregnancies. The majority of the losses occur before the seventh week of gestation usually due to abnormal karyotype of which 52% are trisomies, 20% triploidy and 15% monosomy. Complete Abortion There is complete loss of products of conception with a closed cervix and a thin endometrium on US. Incomplete Spontaneous Abortion There are retained products of conception with continued bleeding associated with a patulous cervix. The retained products may represent pla- cental tissue or fetal tissue. US findings include GS/fluid collection, GS with a dead fetus, endo- metrial thickness >5mm in the majority but thickness may vary from 2 to 5mm; in 14%, thickness may be 2mm or less. Complications
  • 19. 19CHAPTER 1 Early Pregnancy include endometritis, septicaemia, and diffuse intravascular coagulation. Inevitable Abortion The GS becomes detached from its implantation site within the uterus so that abortion becomes inevitable and usually occurs within a few hours. Presentation is usually with PV bleeding <7days, persistent painful uterine contractions, a dilated cervix and ruptured membranes. US findings include a GS low within the uterus, GS surrounded by an anechoic zone of blood and a dilated cervix. Missed Abortion This usually occurs between 8 and 14weeks gesta- tion. There is a dead conceptus within the uterus usually associated with a brownish vaginal dis- charge with a closed cervix. US features include no cardiac activity in the embryo of appropriate size, gestation inappropriate for menstrual age, GS >25mm with no embryo, GS >20mm with- out a YS, misshapen GS, debris within the GS, lack of a double decidual sac, a low sac position (Figure 1-2K) and a subchorionic fluid collection (Figure 1-2G–I). Threatened Abortion This is first trimester PV bleeding associated with a live fetus and closed cervix. The incidence is 20–25% of all clinically apparent pregnancies with a 50% pregnancy loss rate. Fetal viability depends on the detection of fetal heartbeat and movement. Early fetal bradycardia, relative fetal inactivity and the presence of a large subchori- onic haematoma are poor prognostic signs. FETAL ANOMALIES DETECTABLE ON ULTRASOUND IN THE FIRST TRIMESTER Head and Neck • Cystic hygroma • Nuchal translucency • Anencephaly • Large cranial cysts • Exencephaly • Encephalocele • Acrania • Choroid plexus cysts • Dandy–Walker malformation Spine • Neural tube defects • Kyphoscoliosis Ventral • Omphalocele • Gastroschisis • Ectopia cordis • Lateral fold defect Extremities • Short limb dysplasia Heart • Atrioventricular canal defect • Complete heart block Genitourinary • Hydronephrosis • Megacystis (Figure 1-2M) • Cystic dysplastic kidneys Placenta, Umbilical Cord and YS • Partial mole • Umbilical cord cysts • Short cord associated with ventral fold defect • Large YS Multiple Gestation • Monoamniotic twins • Twin–twin transfusion syndrome • Conjoined twins
  • 20. CHAPTER 1 Early Pregnancy20 NB. Most first trimester anomalies are more clearly visualized using TVS. Many serious anom- alies may have a normal sonogram in the first trimester of pregnancy – anencephaly becomes obvious after ossification of the calvarium at or after 12 weeks of menstrual age. FURTHER READING Menstrual Age versus Gestational Age Borrell A, Robinson JN, Santolaya-Forgas J. Report on the 11- to 13+6-week ultrasound evaluation as a screening test for trisomy 21 in singleton pregnancies. Am J Perinatol 2009;26(10):703–10 [Epub 2009 Jun 29. Review]. Dulay AT, Copel JA. First-trimester ultrasound: current uses and applications. Semin Ultrasound CT MR 2008;29(2):121–31 [Review]. Levine D. Ectopic pregnancy. Radiology 2007;245(2): 385–97 [Review]. Levi CC, Dashefsky SM, Holt SC, et al. Ultrasound of the first trimester of pregnancy. Ultrasound Q 1993;11: 95–123. Nyberg DA, Hyett J, Johnson JA, Souter V. First-trimester screening. Radiol Clin North Am 2006;44(6):837–61 [Review]. Sonek J. First trimester ultrasonography in screening and detection of fetal anomalies. Am J Med Genet C Semin Med Genet 2007;145C(1):45–61 [Review]. Thieme GA, Manco-Johnson ML. A pictorial review of normal obstetric ultrasound. Ultrasound Q 2000;15: 106–34. Predictors of Early Pregnancy Failure Bennall GL, Bromley B, Lieberman E, et al. Subchorionic hemorrhage in first-trimester pregnancies: prediction of pregnancy outcome with sonography. Radiology 1996;200:803–6. Carp HJ, Meroni PL, Shoenfeld Y. Autoantibodies as pre- dictors of pregnancy complications. Rheumatology (Oxford) 2008;47(Suppl. 3):iii6–8 [Review]. Doubilet PM, Benson CB, Chow JS. Long-term progno- sis of pregnancies complicated by slow embryonic heart rates in early first trimester. J Ultrasound Med 1999;18:337–41. Goffinet F. Primary predictors of preterm labour. Brit J Obstet Gynaecol 2005;112(Suppl. 1):38–47 [Review]. Grill S, Rusterholz C, Zanetti-Dällenbach R, et al. Poten- tial markers of preeclampsia – a review. Reprod Biol Endocrinol 2009;7:70 [Review]. Harrow MM. Enlarged amniotic cavity: a new sono- graphic sign of early embryonic death. Am J Roent- genol 1992;158:359–62. Jaffe R, Dorgan A, Abramowicz JS. Color Dop- pler imaging of uteroplacental circulation in the first-trimester: value in predicting pregnancy fail- ure or complication. Am J Roentgenol 1995;164: 1255–8. Levi CS, Lyons EA, Cehng XH, et al. Endovaginal US: demonstration of cardiac activity in embryos less than 5mm in CRL. Radiology 1990;176:71–4. Levi SC, Sidney M, Dashefsky SC, et al. Ultrasound in the first trimester. Ultrasound Q 1993;11:95–123. Lindsay DJ, Lovett IS, Lyons EA, et al. Yolk sac diameter and shape on endovaginal US: prediction of preg- nancy outcome in first trimester. Radiology 1992;183: 115–8. Mara E, Foster GS. Spontaneous regression of a yolk sac associated with embryonic death. J Ultrasound Med 2000;19:655–6. McKenna KM, Feldstein VA, Goldstein RB, et al. The empty amnion: a sign of early pregnancy failure. J Ultrasound Med 1995;14:117–21. Ong CY, Liao AW, Spencer K, et al. First trimester mater- nal serum free beta human chorionic gonadotrophin and pregnancy associated plasma protein A as predic- tors of pregnancy complications. Brit J Obstet Gynae- col 2000;107(10):1265–70. Rowling SE, Coleman BC, Langer JE. First-trimester US parameters of failed pregnancy. Radiology 1997;203: 211–7. Stampone C, Nicotra M, Mullinelli C, et al. Transvaginal sonography of the yolk sac in normal and abnormal pregnancy. J Clin Ultrasound 1996;24:3–9. First Trimester Anatomy That May Mimic Fetal Anomaly Borrell A. Promises and pitfalls of first trimester sono- graphic markers in the detection of fetal aneuploidy. Prenat Diagn 2009;29(1):62–8 [Review]. Cyr DR, Mack LA, Nyberg DA, et al. Fetal rhomben- cepalon: normal ultrasound findings. Radiology 1988;166:691–2. Schmidt W, Yarkoni S, Crelin ES, et al. Sonographic visualization of physiologic anterior abdominal wall hernia in the first trimester. Obstet Gynecol 1987;69:911–5. Skibo LK, Lyons EA, Levi CS. First trimester umbilical cord cysts. Radiology 1992;192:719–22. Timor-Tritech IE, Monteaqudo A, Warrent WB. Transvaginal ultrasonographic definition of the central nervous system in the first and early sec- ond trimester. Am J Obstet Gynecol 1991;164: 497–503. Transient First Trimester Fetal Anomalies Babcook CJ, Silvera M, Drake C, et al. Effect of maternal hydration on mild fetal pyelactasis. J Ultrasound Med 1998;17:539–44.
  • 21. 21CHAPTER 1 Early Pregnancy Beke A, Joó JG, Csaba A, et al. Incidence of chromo- somal abnormalities in the presence of fetal sub- cutaneous oedema, such as nuchal oedema, cystic hygroma and non-immune hydrops. Fetal Diagn Ther 2009;25(1):83–92 [Epub 2009 Feb 13]. Borrell A. Promises and pitfalls of first trimester sono- graphic markers in the detection of fetal aneuploidy. Prenat Diagn 2009;29(1):62–8 [Review]. Itoh H, Ihara Y, Sagawa N, et al. Nuchal-fold thicken- ing in Down syndrome fetuses: transient appearance and spontaneous resolution in the second trimester. J Perinat Med 1993;21(2):139–45. Kesrouani AK, Guibourdenche J, Muller F, et al. Etiology and outcome of fetal echogenic bowel. Ten years of experience. Fetal Diagn Ther 2003;18(4):240–6. Knutsen-Larson S, Flanagan JD, Van Eerden P, et al. The first-trimester screen in clinical practice. S D Med 2009;62(10):389, 392–3 [Review]. Raniga S, Desai PD, Parikh H. Ultrasonographic soft markers of aneuploidy in second trimester: are we lost? MedGenMed 2006;8(1):9. Reichler A, Bronshtein M. Early prenatal diagnosis of axil- lary cystic hygroma. J Ultrasound Med 1995;14(8): 581–4. Reynders C, Pauker SP, Benacerraf BR. First trimester isolated nuchal lucency: significance and outcome. J Ultrasound Med 1997;16:101–5. Shields LE, Uhrich SB, Easterling TR, et al. Isolated fetal choroid plexus cysts and karyotype analysis: is it nec- essary? J Ultrasound Med 1996;15:389–94. Shimizu T, Hashimoto K, Shimizu M, et al. Bilateral pleural effusion in the first trimester: a predictor of chromosomal abnormality and embryonic death? Am J Obstet Gynecol 1997;177(2):470–1. Witters I, Fryns JR. Fetal nuchal translucency thickness. Genet Couns 2007;18(1):1–7 [Review]. Intrauterine Fluid Collections That May Mimic a GS Atri M, Bret PM, Tulandi T. Spontaneous resolution of ectopic pregnancy: initial appearances and evalu- ation of transvaginal US. Radiology 1993;186(1): 83–6. Jain KA, Grescovich EO. Sonographic spectrum of pelvic vascular malformations in women. J Clin Ultrasound 1999;27:523–30. Empty GS Angiolucci M, Murru R, Melis G, Carcassi C, Mais V. Association between different morphological types and abnormal karyotypes in early pregnancy loss. Ultrasound Obstet Gynecol 2011 Feb;37(2):219-25. doi: 10.1002/uog.7681. Epub 2010 May 11. Benacerraf BR, Shipp TD, Bromley B. Does the 10-MHz transvaginal transducer improve the diagnostic cer- tainty that an intra-uterine fluid collection is a true gestation sac? J Clin Ultrasound 1999;27:374–7. Dewbury K, Meire H, Cosgrove D. Ultrasound in obstetrics & gynecology. Edinburgh: Churchill Livingston; 2001. Laing FC, Brown DL, Price JF, et al. Intradecidual sign: is it effective in diagnosis of early intrauterine preg- nancy? Radiology 1997;204:655–60. Olson TG, Barnes AA, King JK. Elevated hCG outside of pregnancy – diagnostic considerations and labora- tory evaluation. Obstet Gynecol Survey 2007;62(10): 669–74. Perriera L, Reeves MF. Ultrasound criteria for diagnosis of early pregnancy failure and ectopic pregnancy. Semin Reprod Med 2008;26(5):373–82 [Epub 2008 Sep 29. Review. Erratum in: Semin Reprod Med 2009;27(1):103]. Snyder JA, Haymond S, Parvin CA, et al. Diagnostic con- siderations in the measurement of human chorionic gonadotropin in aging women. Clin Chem 2005; 51(10):1830–5. Risk Groups for EP Chung K, Allen R. The use of serial human chorionic gonadotropin levels to establish a viable or a nonvi- able pregnancy. Semin Reprod Med 2008;26(5):383– 90 [Epub 2008 Sep 29. Review]. Coupet E. Ectopic pregnancy: the surgical epidemic. J Natl Med Assoc 1989;81:567–72. Nama V, Manyonda I. Tubal ectopic pregnancy: diag- nosis and management. Arch Gynecol Obstet 2009 Apr;279(4):443–53 [Epub 2008 Jul 30. Review]. Zacur HA. Expectant management of ectopic pregnancy. Radiology 1993;186:1112. Ultrasound Findings in EP Atri M. Ectopic pregnancy evaluation with endo- vaginal color Doppler flow imaging. Radiology 1993;187(1):19–22. Atri M, Bret PM, Tulandi T. Spontaneous resolution of ectopic pregnancy: initial appearances and evaluation of transvaginal US. Radiology 1993;186:83–6. Barnhart KT. Clinical practice. Ectopic pregnancy. N Engl J Med 2009;361(4):379–87. Brown DL. Diagnosis of ectopic pregnancy with endovagi- nal color Doppler US. Radiology 1993;1187(1):20–2. Brown DL, Doubilet PM. Transvaginal sonography for diagnosing ectopic pregnancy: positive criteria and performance characteristics. J Ultrasound Med 1994;13:259–66. Chandrasekhar C. Ectopic pregnancy: a pictorial review. Clin Imaging 2008;32(6):468–73 [Review]. Chen PC, Sickler GK, Dubinsky TJ, et al. Sonographic detection of echogenic fluid and correlation with cul- diocentesis in evaluation of ectopic pregnancy. Am J Roentgenol 1998;170:1299–302. Fellorito JS, Taylor RJW, Quadanc-Case C, et al. Ecto- pic pregnancy evaluation with endovaginal color flow imaging. Radiology 1992;183:407–11.
  • 22. CHAPTER 1 Early Pregnancy22 Hertzberg BS, Kliewer MA, Bowie JD. Adnexal ring sign and hemoperitoneum caused by hemorrhagic ovarian cyst: pitfalls in the sonographic diagnosis of ectopic pregnancy. Am J Roentgenol 1999;173:1301–2. Levi CS, Lyons EA, Zheng XH, et al. Endovaginal US demonstration of cardiac activity in embryos of less than 5.0mm in crown-rump length. Radiology 1990;176:71. Lin EP, Bhatt S, Dogra VS. Diagnostic clues to ectopic pregnancy. Radiographics 2008;28(6):1661–71 [Review]. Mehta TS, Levine D, Beckwith B. Treatment of ectopic pregnancy: is human chorionic gonadotrophin level of 2000IU/ml a reasonable threshold? Radiology 1997;205:569–73. Mehta TS, Levine D, McArdle CR. Lack of endometrial thickness in predicting the presence of an ectopic pregnancy. J Ultrasound Med 1999;18:117–22. Molloy D, Deambrosis W, Keeping D, et al. Multi- sited (heterotopic) pregnancy after in vitro fertiliza- tion and gamete intrafallopian transfer. Fertil Steril 1990;53:1068. Nyberg DA, Hughes MP, Mack LA, Wang KY. Extra- uterine findings of ectopic pregnancy at transvagi- nal US: importance of echogenic fluid. Radiology 1991;178:823–6. Russell S, Filly RA, Damanto N. Sonographic diagnosis of ectopic pregnancy with EV probes; what really has changed? J Ultrasound Med 1993;12:145. Stein MW, Ricci ZJ, Novak L, et al. Sonographic compar- ison of the tubal ring of ectopic pregnancy with the corpus luteum. J Ultrasound Med 2004;23(1):57–62. Wachsberg RH. Pitfalls in the sonographic diagnosis of ectopic pregnancy. Ultrasound Q 2000;16:89–96. Wachsberg RH. Ectopic pregnancy: recent develop- ments and changing concepts. Ultrasound Q 1998;14:247–53. Wachsberg RH, Karimi S. Sonographic endometrial three- layer pattern in symptomatic first trimester pregnancy: not diagnostic of ectopic pregnancy. J Clin Ultrasound 1998;26:199–201. Differential Diagnosis of EP Dujardin M, Schiettecatte A, Verdries D, et al. Cystic lesions of the female reproductive system: a review. JBR-BTR 2010;93(2):56–61 [Review]. Hertzberg BS, Kliewer MA, Bowie JD. Adnexal ring sign and hemoperitoneum caused by hemorrhagic ovarian cyst: pitfall in the sonographic diagnosis of ectopic pregnancy. Am J Roentgenol 1999;173:1301–2. Parvery HR, Markland N. Pitfalls in transvaginal sono- graphic diagnoses of ectopic pregnancy. J Ultrasound Med 1993;3:139–44. Russell SA, Filly RA, Damato N. Sonographic diagnosis of ectopic pregnancy with endovaginal probes: what really has changed? J Ultrasound Med 1993;3:145–51. Ultrasound Parameters for Measurement of Gestational Age Danon D, Melamed N, Bardin R, et al. Accuracy of ultra- sonographic fetal weight estimation in twin pregnan- cies. Obstet Gynecol 2008;112(4):759–64. Fetal Measurements Working Party. Clinical applications of ultrasound fetal measurements. London: British Institute of Radiology/British Medical Ultrasound Society. Frank P, Hadlock FP. Sonographic estimation of fetal age and weight. Radiol Clin North Am 1990;28:39–51. Goldstein I, Reece EA, Pilu G, et al. Cerebellar measure- ments with ultrasonography in the evaluation of fetal growth and development. Am J Obstet Gynecol 1987;156(5):1065–9. Gottlieb AG, Galan HL. Nontraditional sonographic pearls in estimating gestational age. Semin Perinatol 2008;32(3):154–60 [Review]. Hadlock FP. Ultrasonography in Obstetrics and Gyne- cology. 3rd ed. Philadelphia: WB Saunders; 1994. p. 129–43. Hadlock FP, Deter RL, Harrist RB, et al. Fetal HC: relationship to menstrual age. Am J Roentgenol 1982;138:647–53. Koster MP, Van Leeuwen-Spruijt M, Wortelboer EJ, et al. Lack of standardization in determining gestational age for prenatal screening. Ultrasound Obstet Gyne- col 2008;32(5):607–11. Kurjack A, Crvenkovic G, Salihagic A, et al. Assess- ment of normal early pregnancy by transvaginal color Doppler ultrasonography. J Clin Ultrasound 1993;21(1):3–8. Robinson HD, Fleming JEE. A critical evaluation of sonar crown-rump length measurements. Br J Obstet Gyn- aecol 1975;82:702–10. Lee W, Comstock CH, Kirk JS, et al. Birth weight predic- tion by three-dimensional ultrasonographic volumes of the fetal thigh and abdomen. J Ultrasound Med 1997;16:799–805. Pinette MG, Pan Y, Pinette SG, et al. Estimation of fetal weight: mean value from multiple formulae. J Ultra- sound Med 1999;18:813–7. Meirowitz NB, Ananth CV, Smulian JC, et al. Foot length in fetuses with abnormal growth. J Ultrasound Med 2000;19:201–5. Corpus Luteum in Early Pregnancy Devaseelan P, Fogarty PP, Regan L. Human chorionic gonadotrophin for threatened miscarriage. Cochrane Database Syst Rev 2010;5:CD007422 [Review]. Devoto L, Fuentes A, Kohen P, et al. The human corpus luteum: life cycle and function in natural cycles. Fertil Steril 2009;92(3):1067–79 [Epub 2008 Sep 14. Review]. Durfee SM, Frates MC. Sonographic spectrum of the cor- pus luteum in early pregnancy: gray scale, color and pulsed Doppler. J Clin Ultrasound 1999;27:55–9.
  • 23. 23CHAPTER 1 Early Pregnancy The Cervix in Pregnancy Chao AS, Chao A, Hsieh PC. Ultrasound assessment of cervical length in pregnancy. Taiwan J Obstet Gyne- col 2008;47(3):291–5 [Review]. Crane JM, Hutchens D. Transvaginal sonographic mea- surement of cervical length to predict preterm birth in asymptomatic women at increased risk: a system- atic review. Ultrasound Obstet Gynecol 2008;31(5): 579–87 [Review]. Hertzberg BS, Kliewer MA, Farrell TA, DeLong DM. Spontaneously changing gravid uterus: clinical impli- cations and prognostic features. Radiology 1995;196: 721–4. Kushnir O, Izquierdo L, Smith J, et al. Transvaginal sonographic measurement of cervical length: evalu- ation of twin pregnancy. J Reprod Med 1995;40: 380–2. Ludmin J, Abbott J, Wong G, et al. Vaginal sonography of the cervix in the management of triplet gestation. Am J Obstet Gynecol 1995;172:407. Imseis H, Albert T, Iams J. Identifying twin gestations at low risk for preterm birth with a transvaginal sono- graphic measurement at 24–26weeks gestation. Am J Obstet Gynecol 1997;177:1149–55. Michaels W, Schreiber F, Ager J, et al. Ultrasound sur- veillance of the cervix in twin gestation: management of cervical incompetence. Obstet Gynecol 1991;78: 739–49. Wong G, Levine D. Sonographic assessment of the cervix in pregnancy. Semin Ultrasound CT MRI 1998;19: 370–80. Abortion Achivon R, Achron A, Yagel S. First trimester for trans- vaginal sonographic diagnosis of Dandy–Walker mal- formation. J Ultrasound Med 1993;21:62–4. Allison JL, Schust DJ. Recurrent first trimester preg- nancy loss: revised definitions and novel causes. Curr Opin Endocrinol Diabetes Obes 2009;16(6):446–50 [Review]. Bennett JC, Burlbaw J, Drake CK, et al. Diagnoses of ectopia cordis at 12weeks gestation using transab- dominal ultrasonography with color flow Doppler. J Ultrasound Med 1991;10:695–6. Cicero S, Sacchini C, Rembouskos G, et al. Sonographic markers of fetal aneuploidy – a review. Placenta 2003;24(Suppl. B):S88–98. Cullen MT, Green J, Whetham J, et al. Transvaginal ultrasonographic detection of congenital anomalies in the first trimester. Am J Obstet Gynecol 1990;163: 466–76. Goldstein RD, Filley RA. Prenatal diagnoses of anen- cephaly: spectrum of sonographic appearances and distinction from the amniotic band syndrome. Am J Roentgenol 1988;51:547–50. Timor-Tritsch IE, Monteaqudo A, Peisner DB. High fre- quency transvaginal sonographic examination for the potential malformation assessment of the 9week to 14week fetus. J Clin Ultrasound 1992;20:231–8. Van Zalen-Sprock RM, van Vugt JM, van Geijn HP. First and early second trimester diagnosis of anoma- lies of the central nervous system. J Ultrasound Med 1995;14:603–10.