Regarding chromosomal aberrations in spontaneous miscarriages...

A 24-year-old woman has had three first-trimester spontaneous miscarriages.
Which of the following statements concerning chromosomal aberrations in miscarriages is true?
a. 45,X is more prevalent in chromosomally abnormal term babies than in abortus products
b. Approximately 20% of first-trimester spontaneous abortions have chromosomal abnormalities
c. Trisomy 21 is the most common trisomy in abortuses
d. Despite the relatively high frequency of Down syndrome at term, most Down fetuses abort spontaneously
e. Stillbirths have twice the incidence of chromosomal abnormalities as live births

Answer:
d. Despite the relatively high frequency of Down syndrome at term, most Down fetuses abort spontaneously

Discussion: Chromosomal abnormalities are found in approximately 50% of spontaneous abortions,
5% of stillbirths, and 0.5% of live born babies.
In spontaneous losses, trisomy 16 is the most common trisomy, with 45,X the most common single abnormality found. At term, trisomy 16 is never seen and 45,X is seen in approximately 1 in 2000 births. It is estimated that 99% of 45,X and 75% of trisomy 21 conceptuses are lost before term.