Deck 17: Prenatal Diagnosis and Screening

Question 1

During which weeks of pregnancy is chorionic villus sampling generally performed?

A) 6 to 8 weeks
B) 10 to 12 weeks
C) 16 to 18 weeks
D) 20 to 22 weeks
E) 24 to 26 weeks

Answer 1

10 to 12 weeks

Question 2

What is one disadvantage of chorionic villus sampling compared to amniocentesis?

A) It is done later in pregnancy
B) It is more invasive
C) It is associated with a high rate of complications
D) It is associated with a higher rate of ambiguous results
E) It must be done on an inpatient basis

Answer 2

It is associated with a higher rate of ambiguous results

Question 3

The results of a second trimester screen for your patient are the following: Low levels of unconjugated estriol
Low levels of maternal serum α-fetoprotein
High levels of free $\beta$ -human chorionic gonadotropin
With what fetal disorder are these results consistent?

A) Trisomy 13
B) Trisomy 18
C) Trisomy 21
D) Neural tube defect
E) Not enough information is provided

Answer 3

Trisomy 21

Question 4

Why is an accurate estimate of gestational age necessary before maternal serum α-fetoprotein (MSAFP) is measured?

A) It is only expressed early in pregnancy
B) It is only expressed in the second trimester of pregnancy
C) One must relate the MSAFP measurement to gestational age because the MSAFP levels change during the pregnancy
D) If it is too late in the pregnancy to do more invasive testing, it's not worth doing MSAFP measurements
E) Because it takes several days to do the MSAFP testing, it can be skipped and invasive testing if the pregnancy is beyond 16 weeks can be done

Question 5

Which of the following is associated with an increased level of maternal serum α-fetoprotein?

A) Down syndrome
B) Edward syndrome
C) Neural tube defect
D) Advanced maternal age
E) Cleft palate

Question 6

For the majority of metabolic disorders, what is the recurrence risk in a family that has had an affected child?

A) The general population risk
B) 25%
C) 33%
D) 50%
E) 100%

Question 7

Nutritional supplementation of pregnant women with which of the following reduces the risk of neural tube defects in the fetus?

A) Vitamin A
B) Iron
C) Calcium
D) Folic acid
E) Vitamin K

Question 8

What is the leading indication for prenatal testing in the United States?

A) A previous child with Down syndrome
B) Spotting during pregnancy
C) Advanced maternal age
D) A previous child with any autosomal dominant genetic disorder
E) A previous child with any autosomal recessive disorder

Question 9

Which of the following is a procedure that is used for prenatal genetic testing?

A) Maternal serum testing
B) Fetal serum testing
C) Ultrasound
D) Chorionic villus sampling
E) Nuchal translucency

Question 10

Why not lower the cutoff on maternal serum α-fetoprotein screens so that near complete ascertainment of neural tube defects via the screen would be had?

A) It would be too expensive
B) There would be too many false positives
C) It would decrease the sensitivity for Down syndrome detection
D) MSAFP levels that low cannot be measured
E) It would no longer be possible to discriminate between the common trisomies via maternal serum screening

Question 11

What concern should arise when confined placental mosaicism is found for trisomy 15?

A) Trisomy 15 in the fetus
B) Uniparental disomy for chromosome 15 in the fetus
C) Placental insufficiency
D) Pseudomosaicism for trisomy 15
E) A or D

Question 12

Which of the following is NOT a component of first-trimester screening for aneuploidies?

A) Measurement of pregnancy-associated plasma protein A (PAPP-A) in maternal serum
B) Measurement of human chorionic gonadotropin
C) Nuchal translucency measurements
D) Maternal serum α-fetoprotein
E) Precise ultrasound examination

Question 13

Which of the following are prenatal screens that might indicate a need for further testing?

A) Maternal serum testing
B) Chorionic villus sampling
C) Amniocentesis
D) Placental biopsy
E) Fundal height

Question 14

Which of the following is an advantage of prenatal biochemical testing for metabolic disorders compared to genetic testing?

A) Can be done earlier in pregnancy
B) The test is less invasive
C) It detects an effect caused by any mutant allele for the gene of interest
D) A smaller sample is required
E) There's no risk of maternal contamination