216 Obstetrics and Gynecology Board Review •••
❍ What is the only etiologic factor conclusively linked to an increased risk of trisomy?
Advanced maternal age.
❍ Chromosome analysis on your patient’s husband revealed the following: 45,XY, der(14;21)(q10;q10).^
What would you discuss with this couple?
He is a carrier of a balanced 14:21 translocation. There is an increased risk of offspring with Down syndrome,
recurrent pregnancy loss, decreased fertility, or uniparental disomy (UPD). Carriers of this translocation do not
typically have developmental or phenotypic abnormalities.❍ Your patient reports that her brother has a son with trisomy 21 and she is concerned about her risk to have
a child with Down syndrome. What would you discuss with her?
Her risk of Down syndrome would be greater than her age-related risk. Trisomy 21 is typically a sporadic
occurrence (and is not inherited in families; however, you do not have documentation that it is a true trisomy;
therefore, peripheral blood chromosomes need to be offered to rule out a familial translocation).
❍ What meiotic process is the major cause of aneuploidy?
Nondisjunction.
❍ What percentage of fetuses with 45,X (Turner syndrome) spontaneously abort?
99%.