Obstetrics Flashcards
At what hCG level should you expect to visualize an intrauterine gestational sac?
2000 IU
What is the optimal gestational age for the First Trimester Screen?
11 weeks 0 days to 13 weeks 6 days
What is the optimal crown rump length for the First Trimester Screen?
45-84 mm
What 4 elements comprise the First Trimester Screen?
- Fetal nuchal translucency
- Maternal age
- PAPP-A
- BhCG
Which chromosome abnormalities are assessed with the First Trimester Screen?
Trisomy 13 (Patau syndrome) Trisomy 18 (Edwards syndrome) Trisomy 21 (Down syndrome)
What are the 2 components of the serum biochemistry for the First Trimester Screen?
- Free beta hCG
- PAPP-A
What is measured during a Triple Screen? Quadruple Screen?
- AFP, unconjugated estriol, and beta-hCG
- Quad screen includes inhibin A
What findings are diagnostic of pregnancy failure (4) (NEJM 2013)?
- Crown-rump length of >= 7 mm and no heartbeat
- Mean sac diameter of >= 25 mm and no embryo
- Absence of embryo with heartbeat >= 2 wk after a scan that showed a gestational sac without a yolk sac
- Absence of embryo with heartbeat >= 11 days after a scan that showed a gestational sac with a yolk sac.
* If criteria not met, then repeat US in 7-10 days if stable
* Can follow bhCG levels too
When is the best time to do a routine anatomy scan?
18-20 weeks, favour closer to 20 weeks
At what cervical length would the obstetrician consider cerclage?
Less than 25 mm
Close follow up 25-30 mm
Greater than 30 mm is normal
How do you measure the biparietal distance?
Outer table to inner table at the level of the thalami and cavum septum pellucidum.
How do you measure the abdominal circumference?
Abdo circumference should be determined at the skin line on a true transverse view at the level of the fetal liver, just below the heart, using the landmark of the umbilical portion of the left portal vein at its junction with the portal sinus and right portal vein.
What is a normal amniotic fluid index (AFI)?
Take the largest AP fluid pocket in each quadrant; and add the four measurements together.
Normal is between 7 and 25 cm
(US Requisites)
What makes up the Biophysical Profile (BPP)?
Five tests are combined: four are of the fetus (assessing acute hypoxia) evaluating cardiac function, breathing, gross body movement, and overall tone, and one is of the amniotic fluid (assessing chronic hypoxia). The non stress test uses an external monitor to analyze cardiac function. The other four are evaluated by US. Scored from 0 to 10.
What is considered small for gestational age (SGA)?
Less than the 10th percentile for birth weight
What is the value of the BPP score?
The fetus with a BPP score of 7 or more can be considered “safe” in most cases for up to a week.
When should you be able to see a gestational sac? An embryo? A yolk sac?
- Gestational sac usually can be seen at 5 weeks GA on TVUS
- Embryo routinely seen at about 6 weeks GA on TVUS
- Yolk sac often identified at 5.5 weeks GA on TVUS
When can cardiac motion be detected?
- Transabdominally, heart motion is detected in all embryos with a CRL larger than 9 mm (6.9 weeks).
- Transvaginally, heart motion is detected in all normal embryos larger than 5 mm (6.2 weeks). In most cases it can be detected even earlier.
When does bowel normally return to the abdominal cavity in a normal fetus?
by 12 weeks
What is the classic clinical triad for hydatiform mole?
1) enlarged uterus
2) hyperemesis
3) Beta hCG markedly elevated (often >100,000 mIU/L)
T or F. A partial mole is usually triploid.
True
Choroid plexus cysts should raise suspicion for which disease?
Trisomy 18. Other findings include: cardiac anomalies, clenched hands (especially with overlapping index finger), a small or absent nasal bone, and a cleft lip/palate.
What are typical US findings of trisomy 21?
Minor markers for trisomy 21 include nuchal fold thickening and echogenic spots in the bowel or heart. Other markers include clinodactyly, not clenched hands as seen here.
Major anomalies in trisomy 21 include cardiac defects, as well as duodenal atresia and esophageal atresia.
What are typical US findings of trisomy 13?
- The hallmark brain finding in T13 is holoprosencephaly.
- Fetuses with T13 are more likely to have a midline or bilateral cleft lip/palate, rather than the unilateral cleft lip/palate.
- The typical hand finding for T13 is polydactyly, not clenched hand with overlying index finger.
- Rocker-bottom or clubbed feet
- Cardiac defects are common (50%). Hypoplastic left heart or ventriculoseptal defect
- Abdo findings: enlarged and echogenic kidneys with or without hydro, omphalocele, bladder extrophy, and echogenic bowel
- Single umbilical artery and papillary muscle calc have also been reported.