Prenatal Diagnosis Flashcards
Describe the differences between screening tests and diagnostic tests.
• Screening:
- assess risk
- quick
- high NPV
- low FPs
•Diagnostic:
- can run in or out
- longer
- usually definitive
In general, prenatal screening is not for patients ____________.
who do not want to know; who would not accept results; who would not change anything for the family or for the medical management
We don’t make management decisions on ___________ results.
screening
Maternal blood tests for cell-free fetal DNA is considered a ______________.
screening test
To ensure their safety, ultrasounds have sensors telling you if ____________.
you’ve been in one place too long (which could theoretically heat fluids)
The most important use of the first-trimester ultrasound is ________________.
to determine the due date
_______________ (which can be determined by vaginal ultrasound) is predictive of preterm delivery.
Cervical length
The gestational sac is only measured during ____________.
the first trimester (when the fetus is too small to be meaningfully measured)
The best indicator of gestational age and growth during the second trimester is _________.
the averaged percentiles of multiple measurements (femur, skull, etc.)
Generally, NTDs present with elevated ________.
AFP
Trisomy 18 presents with what abnormal serum analytes?
Decreased levels of everything: AFP, hCG, inhibin A, and PAPP
Trisomy 21 presents with low _________ and elevated ___________.
AFP; hCG and inhibin A
Currently, the best screening test for Down syndrome is _______________.
cell-free DNA
Where is AFP made?
In the fetal liver
In general, ultrasounds can more accurately determine age when ____________.
they’re done earlier in the pregnanccy
Elevated AFP can also be ________________.
things other than NTDs
multiple gestations, hemorrhage, gastroschisis, or placental abnormalities
Nuchal thickening can indicate _____________.
Down syndrome
What can chorionic villus testing indicate?
DNA and metabolic abnormalities
Notably, it cannot detect AFP so NTDs will not be seen.
What is used to gauge the age of the fetus?
Prior to 12 weeks, crown-rump length is used. After 12 weeks the fetus bends and the spine is less reliable so parietal distance is used.
What is PUBS used for?
Because of the high complication rate (1%), it is used only for suspicion of fetal anemia or infection.
