Prenatal Diagnosis Flashcards

1
Q

Describe the differences between screening tests and diagnostic tests.

A

• Screening:

  • assess risk
  • quick
  • high NPV
  • low FPs

•Diagnostic:

  • can run in or out
  • longer
  • usually definitive
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2
Q

In general, prenatal screening is not for patients ____________.

A

who do not want to know; who would not accept results; who would not change anything for the family or for the medical management

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3
Q

We don’t make management decisions on ___________ results.

A

screening

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4
Q

Maternal blood tests for cell-free fetal DNA is considered a ______________.

A

screening test

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5
Q

To ensure their safety, ultrasounds have sensors telling you if ____________.

A

you’ve been in one place too long (which could theoretically heat fluids)

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6
Q

The most important use of the first-trimester ultrasound is ________________.

A

to determine the due date

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7
Q

_______________ (which can be determined by vaginal ultrasound) is predictive of preterm delivery.

A

Cervical length

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8
Q

The gestational sac is only measured during ____________.

A

the first trimester (when the fetus is too small to be meaningfully measured)

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9
Q

The best indicator of gestational age and growth during the second trimester is _________.

A

the averaged percentiles of multiple measurements (femur, skull, etc.)

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10
Q

Generally, NTDs present with elevated ________.

A

AFP

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11
Q

Trisomy 18 presents with what abnormal serum analytes?

A

Decreased levels of everything: AFP, hCG, inhibin A, and PAPP

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12
Q

Trisomy 21 presents with low _________ and elevated ___________.

A

AFP and PAPP; hCG and inhibin A

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13
Q

Currently, the best screening test for Down syndrome is _______________.

A

cell-free DNA

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14
Q

Where is AFP made?

A

In the fetal liver

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15
Q

In general, ultrasounds can more accurately determine age when ____________.

A

they’re done earlier in the pregnanccy

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16
Q

Elevated AFP can also be ________________.

things other than NTDs

A

multiple gestations, hemorrhage, gastroschisis, or placental abnormalities

17
Q

Nuchal thickening can indicate _____________.

A

Down syndrome

18
Q

What can chorionic villus testing indicate?

A

DNA and metabolic abnormalities

Notably, it cannot detect AFP so NTDs will not be seen.

19
Q

What is used to gauge the age of the fetus?

A

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.

20
Q

What is PUBS used for?

A

Because of the high complication rate (1%), it is used only for suspicion of fetal anemia or infection.