602 Obstetrics and Gynecology Board Review •••
❍ What is the prevalence of major chromosomal abnormalities being present in either partner of a couple with
two or more pregnancy losses?
Four to eight percent of couples with recurrent pregnancy loss one or the other partner may have a chromosomal
abnormality, usually a balanced translocation.
❍ What is the most common single type of karyotypic abnormality present in SAB?
Aneuploidy especially trisomies.
❍ What percentage of first-trimester SABs have karyotypic abnormalities?
50%.
❍ What percentage of second trimester?
30%.
❍ What percentage of stillbirths?
3%.
❍ What are the most common types of abnormal karyotypes found?
Trisomy (50%), monosomy 45,X (20%), triploidy (10%), and structural abnormalities (5%).
❍ What is the most common single chromosomal abnormality?
45,X.
❍ What is the occurrence of uterine anomalies in those with repeated abortion?
10% to 15%.
❍ What is the most common uterine anomaly?
Septate uterus.
❍ What is the etiology of uterine anomalies?
Müllerian ducts fusion defects that occur between 6 and 10 weeks in fetal development
❍ Is the prevalence of urinary tract anomalies increased in patients with all uterine malformations?
Only for those with unicornuate/bicornuate uterus or uterus didelphys, NOT in those with septate uterus.
❍ What is the approximate incidence of SAB associated with the unicornuate uterus?
34%.
❍ What is the SAB rate for those with a bicornuate uterus?
Only slightly higher than the normal population
❍ What is the SAB rate for those with a septate uterus?
21% to 44%.