Maternal Serum Screening

Question 1

What are the real implications of the results from a screening test?

Answer 1

Positive Test = risk increased
Negative Test = risk decreased

Question 2

Positive Predictive Value

Answer 2

The likelihood a pregnancy is affected when screening indicates a positive or high-risk result

Question 3

Negative Predictive Value

Answer 3

The likelihood a pregnancy is unaffected when screening indicates a negative or low risk result

Question 4

What does the First Trimester Screen test screen for?

Answer 4

Down syndrome
trisomy 18

Question 5

What is a normal NT (nuchal translucency) measurement?

Answer 5

< 3.0 mm

Question 5

What are the implications of an increased NT?

Answer 5

Increased NT is an independent risk factor for increased risk of aneuploidy, even if analytes are normal.

Question 6

All of hte anlytes are produced by the placenta in FTS except for…

Answer 6

AFP

Question 7

What are the 2 main analytes tested during FTS and what is their typical pattern?

Answer 7

Pregnancy-associated plasma protein A (PAPP-A): Rises throughout pregnancy
Human chorionic gonadotropin (hCG): rises rapidly until 10 weeks gestation then declines

Question 8

How long is normal, healthy pregnancy?

Answer 8

40 weeks

Question 9

What levels of PAPP-A & hCG are associated with trisomy 18?

Answer 9

both are decreased
(all analytes are low in trisomy 18)

hCG is also low during 2nd trimester screen for trisomy 18

Question 10

What levels of PAPP-A & hCG are associated with Down syndrome?

Answer 10

hCG tends to be increased and PAPP-A tends to be decreased

hCG is also high in 2nd trimester for Downs

Question 11

What value for MoM is considered normal?

Answer 11

1

Question 12

What risk does poorly controlled diabetes pose to a fetus?

Answer 12

open neural tube defects

Question 13

When is AFP ordered and what does its level tell us?

Answer 13

Second trimester
Increased AFP is associated with ONTD

Question 14

Most analytes are made by the placenta, where is AFP made though?

Answer 14

the yolk sac, fetal GI tract, and fetal liver

Question 15

When is the Quad Screen ordered and what conditions is it screening for?

Answer 15

2nd trimester
Downs, trisomy 18, ONTD

Question 16

What pattern on the Quad Screen is indicative of Downs?

Answer 16

b-HCG = high
uE3 = low
Inhibin-A = high
AFP = low

Question 17

What pattern on the Quad Screen is indicative of trisomy 18?

Answer 17

b-HCG = low
uE3 = low
AFP = low

Question 18

Other than ONTD, what can abnormal AFP levels be indicative of?

Answer 18

anencephaly

Question 19

Why is accurate gestational dating so important?

Answer 19

So that the lab knows which levels of analytes to expect for comparison, otherwise results are not reliable.

Question 20

Which conditions are associated with very low levels of uE3?

Answer 20

• Smith-Lemli-Opitz syndrome (SLO)
• steroidsulfatase deficiency (X-linked ichthyosis).

Usually discussed only when the MoM is < 0.3

this was on the midterm

Question 21

Increased AFP can be associated with what condition other than ONTD?

Answer 21

ventral wall defects

Can see MoM values >7

Question 22

In the setting of a normal ultrasound, what can be an explanation for increased AFP?

Answer 22

Bleeding in pregnancy

Question 23

What is associated with very high levels of AFP? (MoM > 10)

Answer 23

congenital Finnish nephrosis

MoM is usually more like 20-30

Question 24

Very high or very low analytes may be an indication of …

Answer 24

placental insufficiency