Obstetrical Ultrasound

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Obstetrical Ultrasound• Introduced in the late 1950’s ultrasonography is a safe, non- invasive, accurate and cost-effective means to investigate the fetus• Computer generated system that uses sound waves integrated through real time scanners placed in contact with a gel medium to the maternal abdomen• The information from different reflections are reconstructed to provide a continuous picture of the moving fetus on the monitor screen

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Obstetrical Ultrasound

  1. 1. Obstetrical Ultrasound By La Lura White M.D. Maternal Fetal Medicine
  2. 2. Obstetrical Ultrasound• Introduced in the late 1950’s ultrasonography is a safe, non- invasive, accurate and cost-effective means to investigate the fetus• Computer generated system that uses sound waves integrated through real time scanners placed in contact with a gel medium to the maternal abdomen• The information from different reflections are reconstructed to provide a continuous picture of the moving fetus on the monitor screen
  3. 3. Obstetrical Ultrasound• Indications:• Unsure last menstrual period• Vaginal bleeding during pregnancy• Uterine size not equal to expected for dates• Use of ovulation-inducing drugs confirm early pregnancy• Obstetric complications in a prior pregnancy: ectopic, preterm delivery• Screen for fetal anomaly: abnormal serum screens, certain drug exposure in early pregnancy, maternal diabetes. Rhisoimmunization• Postdate fetus• Twins (monochorionic)• Intrauterine growth restriction (IUGR)RADIUS study (1993) did not support routine US screening
  4. 4. Obstetrical Ultrasound• 1st. Trimester (less than 12 weeks)• Gestational sac location / size / shape• Embryo• Yolk sac• Amnion• Fetal cardiac activity• Placental position/Umbilical cord• Amnionitic fluid• Fetal morphology>11 weeks)• Cranium• Heart• Stomach/Bladder/Cord insertion/presence of limbs, hands and feet
  5. 5. Obstetrical Ultrasound• Pre and peri-ovulation (1-2 weeks): ovarian follicle matures and ovulation• Conceptus (3-5 weeks): Corpus luteum, fertilization, morula, blastocyst, bila minar embryo• Embryonic (6-10 weeks): Trilaminar C- shaped embryo• Fetal Phase: (11-12 weeks):
  6. 6. Obstetrical Ultrasound (TVU)Gestational sac: seen at 4 weeks, fluidfilled with echogenic border, grow at least0.6 mm daily.15Yolk sac: 33 days (4.7 wk)Embryonic echoes: 38 days (5.4 w) withembryo at 6 wkIn a normal pregnancy, the embryo shouldbe visible if the gestational sac is 25 mmor larger in diameter.
  7. 7. Obstetrical Ultrasound• An intrauterine gestational sac should be visualized by transvaginal ultrasound with β-hCG values between 1000 and 2000 IU and abdominal exam 5500-6500 IU• Visible heart activity: 43 days (6.1w)• Normal heart rate at 6 weeks: 90-110 bpm• At 9 weeks:140-170 bpm.• At 8-9 weeks if nl heartbeat: no bleeding 3%loss bleeding 13% loss• At 5-8 weeks a bradycardia (<90 bpm) is associated with a high risk of miscarriage.
  8. 8. Obstetrical Ultrasound• CRL(Crown Rump Length):• Longest length excluding limbs and yolk sac• Made between 7 to 13 weeks• 3 days: 7-10 weeks• 5 days: 10-14 weeks• Fetal CRL in centimeters plus 6.5 equals gestational age in weeks
  9. 9. Obstetrical Ultrasound• Ultrasound findings in a pregnancy destined to abort include:• A poorly-defined, irregular gestational sac• A large yolk sac (6 mm or greater in size)• Low site of sac location in the uterus• Empty gestational sac at 8 weeks gestational age (the blighted ovum).
  10. 10. Obstetrical Ultrasound• First Trimester Screening• In 2007, the American College of Ob Gyn endorsed offering aneuploidy screening to all gravidas• Performed between 11 and 13 weeks 6 days (fetal crown–rump length 42–79 mm).• Fetal nuchal translucency and maternal blood, β-hCG and pregnancy-associated plasma protein A (PAPP-A).• This test can detect approximately 60-85% of fetuses with Down syndrome, with a 5% false positive rate.2• Abnormal screen can increase the risk of genetic, other aneuploidiesand other cardiac anomalies
  11. 11. Obstetrical Ultrasound• Nuchal translucency:• Translucent space between the back of the neck and the overlying skin• The scan is obtained with the fetus in sagittal section and a neutral position .• The fetal head (neither hyperflexed nor extended, either of which can influence the nuchal translucency thickness).• The fetal image is enlarged to fill 75% of the screen, and the maximum thickness is measured, from leading edge to leading edge. (inner to inner measurement)• It is important to distinguish the nuchallucency from the underlying amnionic membrane.• > 6 mm considered abnormal
  12. 12. Obstetrical Ultrasound• 2nd Trimester Ultrasound (13 weeks-24 weeks)• Fetal survey:• Fetal number• Viability• Presentation• Fetal biometry• Amnionitic fluid• Placenta• Cervix• Fetal Anatomic screening
  13. 13. Obstetrical Ultrasound• Cervical length• Endovaginal probe, examine in dorsal lithotomy position with empty bladder• Normal cervix should have a length of 2.5cm or more from 10 weeks gestation until 36 week• The width of the cervical canal at the level of the internal os should be less than 4mm• Document any evidence of funneling• Optimal gestational age for cervical length assessment is after 16 to 20 weeks gestation• Assessment 20-24 weeks best time evaluation PTD
  14. 14. Obstetrical Ultrasound• Transvaginal probe• Full bladder• Cervical Length: internal os to external os
  15. 15. Obstetrical Ultrasound • Funneling (percentage): internal os to end of funneling over total cervical length)
  16. 16. Obstetrical Ultrasound• BPD:• Greatest accuracy between 12-28 weeks (better>14 wks.)• The plane for measurement of head circumference (HC) and bi-parietal diameter (BPD)must include:• Cavum septum pellucidum• Thalamus• Choroid plexus in the atrium of the lateral ventricles.• Measure outer table of the proximal skull to the inner table of the distal• HC:• Measure the longest AP length• (BPD + OFD) X 1.62
  17. 17. Obstetrical Ultrasound• Abdominalcircumference• Determined on transverse view atthe level of thejunction of the umbilical vein, portal sinus,and fetal stomach• Measured from the outer diameter to outer diameter• Multiply mean diameter by 3.14• Assessing fetal weight/IUGR/macrosomia
  18. 18. Obstetrical Ultrasound• Femur Length (FL):• Aligning the transducer with the lower end of the fetal spine and rotating toward the ventral aspect of the fetus• Can measure from 10 weeks onward• Measurement origin to distal end of shaft and shows two blunted ends• Do not include femoral head or distal epiphysis• Femur image is at an angle of less than 30 degrees to the horizontal.• It increases from about 1.5 cm at 14 weeks to about 7.8 cm at term.• Humerus• Measured similarly
  19. 19. Obstetrical Ultrasound• Amnionitic Fluid• AFI: measure four quadrants of largest verticle pocket• 5-20 cm. nl, 6-8 cm. borderline,<5 cm oligohydramnios• Polyhydramnios is defined as an amniotic fluid volume in excess of 2000 mL. A single pocket of fluid that is 8 cm or larger
  20. 20. Obstetrical Ultrasound Grade 0• Placenta:• Determining its upper and lower edges r/o placenta previa• With increasing gestational age, the placenta increases in echogenicity because of increased Grade 1 fibrosis and calcium content.• This feature of placental maturation has led to a grading of placentas from immature (grade 0) to mature (grade 3).• Placentolmegaly Grade 3 Diabetes, fetal hydrops, Rhisoimmunization• Small placenta:• Severe IUGR (symmetrical/asymmetrical)
  21. 21. Obstetrical Ultrasound • Abnormal placentas • Placenta Previa • found in approximately 5% of second-trimester scans • If detected at 15–19 weeks, it persists in 12% of patients. • If it is detected at 24–27 weeks, it may persist in up to 50%. • VasaPrevia:membranous insertion of cord where exposed vessels cross internal os
  22. 22. Obstetrical Ultrasound• Fetal anatomy:• Head• Atrium of lateral ventricles• Choroid plexus assessment• Cerebellum• Cisterna magna• Nuchal fold
  23. 23. Obstetrical Ultrasound• The atrium of lateral ventricles should be less than 10mm in diameter (best measured at the occipital horn).• The choroid plexii should be homogenous.• Small, and sometimes multiple, choroid plexus cysts are a common finding on high resolution equipment.• They are of doubtful significance as an isolated finding.
  24. 24. Obstetrical UltrasoundThe cerebellar diameter should approximately equal the weeks of gestation.(Ex: 19weeks=19mm)Cisterna magna: < 10mmNuchal fold: (outer edge of occipital bone to skin surface )<6mm (between 17-20weeks).
  25. 25. • Face:• Profile• Nasal bone• Nose• Lips
  26. 26. Obstetrical Ultrasound• Thorax• Lung volumes• Diaphphram• r/o CCAM• Congenital diaphragmatic hernia
  27. 27. Obstetrical Ultrasound• Fetal Circulation• Blood from the placenta is carried to the fetus by the umbilical vein• About half of this enters the fetal ductusvenosus and is carried to the inferior vena cava• The other half enters the liver proper from the inferior border of the liver.• The branch of the umbilical vein that supplies the right lobe of the liver first joins with the portal vein.• The blood then moves to the right atrium of the heart.• In the fetus, there is an opening between the right and left atrium (the foramen ovale), and most of the blood flows through this hole directly into the left atrium from the right atrium, thus bypassing pulmonary circulation.• The continuation of this blood flow is into the left ventricle, and from there it is pumped through the aorta into the body
  28. 28. Obstetrical Ultrasound– Some of the blood entering the right atrium does not pass directly to the left atrium through the foramen ovale, but enters the right ventricle and is pumped into the pulmonary artery.– In the fetus, there is a connection between the pulmonary artery and the aorta, called the ductusarteriosus, which directs most of this blood away from the lungs
  29. 29. Obstetrical Ultrasound• Cardiac Anatomy• Four-Chamber View of the Heart• The ultrasound beam is directed perpendicular to the midchest plane at the level of the heart.• These chambers consist of the right and left atrial and both ventricular chambers• Corresponding valves between themhttp://www.fetal.com/FetalEcho/04%20Standard.html
  30. 30. Obstetrical Ultrasound• The heart is approximately one-third the area of the chest, inclined to the left 45 degrees to the midline.• The AP midline passes through the left atrium and the right ventricle• The midline (AP) and the cardiac axis (arrowhead on dashed line) intersect and form the angle shown• Look for asymmetry in chamber size, defects in the septum or displacement of the heart• Detection rate 60-75% for anomalies with 4 chamber view, higher with outflow tracts
  31. 31. Obstetrical Ultrasound• Sweep the transducer beam in a transverse plane from the level of the four chamber view towards the fetal neck• Right Outflow Tract Left Outflow Tract• Right outflow track comes Comes off left ventricle off right ventricle and bifurcates continues into aortic arch continues into pulmonary artery and then to descending aorta
  32. 32. Obstetrical Ultrasound• Detect Fetal Heart Rate• M-mode
  33. 33. Obstetrical Ultrasound • Abdomen/Stomach (presence, size, and situs) • Liver
  34. 34. • Cord Insertion:• Ensure the abdominal wall around the cord insertion is intact• No bowel has herniated into the cord.• 3-vessel
  35. 35. Obstetrical Ultrasound• Kidneys/Bladder• Kidneys• Confirm the presence and position of both kidneys.• Look for the anechoic renal pelvis.• The renal pelvis TS diameter should be less than 5mm.
  36. 36. Obstetrical Ultrasound• Abnormal• Renal:• urethral atresia: large fetal bladder (bl), urinary ascites (asc), and hydronephrotic kidneys• Posterior urethral valves with keyhole bladder
  37. 37. Obstetrical Ultrasound• Spine:• Coronal or Sagital of entire spine:• cervical• Thoracic• Lumbar• Sacral• Transverse assessment of entire spine
  38. 38. Obstetrical Ultrasound Upper Extremities Normal AbnormalFist clenched Phocomelia
  39. 39. Obstetrical Ultrasound• Lower Extremities:
  40. 40. Obstetrical Ultrasound• Abnormal Ultrasounds• Omphalocele• Gastrochesis
  41. 41. Obstetrical Ultrasound• Doppler Ultrasound• Blood flow characteristics in the fetal blood vessels can be assessed with Doppler flow velocity waveforms‘• Diminished flow, particularly in the diastolic phase of a pulse cycle is associated with compromise in the fetus.• Various ratios of the systolic to diastolic flow are used as a measure of this compromise.• The blood vessels commonly interrogated include the umbilical artery, the aorta, the middle cerebral artery, ductusvenosus (DV) and umbilical vein (UV)• Abnormal uterine artery Doppler velocimetry and pre-eclampsia, intra- uterine growth retardation and adverse pregnancy outcomes.
  42. 42. Doppler Ultrasound• Ductusvenosus leads directly into the vena cava to allows some blood rich in oxygen and nutrients to be pumped out of the body without passing through the capillary beds in the kidney.• Abnormalwaveforms in the ductusvenosus may be key to predicting right heart failure in the hypoxic fetus and an important indicator of imminent fetal demise (Kiserud 1991).• Reversed flow in the ductusvenosus is an ominous sign.
  43. 43. Doppler Ultrasound • The umbilical artery is evaluated measuring the blood flow velocity at peak systole (maximal contraction of the heart) and peak diastole (maximal relaxation of the heart) • These values are computed into different ratios like S/D or RI
  44. 44. Doppler Ultrasound • Predict fetuses at risk for anemia or hydrops especially Rhalloimmunized pregnancies • >1.5 MOM or ratios can be used
  45. 45. Obstetrical Ultrasound• Three-Dimensional Ultrasound3D• Display multiple longitudinal, transverse, and coronal images.• Images may improve the accuracy of anomaly detection of the fetal face, ears, and distal extremities
  46. 46. Obstetrical Ultrasound• Abnormal 3D Images Cleft lip Cyclopia
  47. 47. Obstetrical Ultrasound• 4D Ultrasounds that adds the element of time to the 3D process.• Offers live images• Fetal changes like movement, kicking, reach with hands and facial expressions can be seen
  48. 48. Obstetrical Ultrasound
  49. 49. Obstetrical Ultrasound• We invite you to visit our website:• www.secondopinion2.com• info@secondopinion2.com

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