Fetal death rates in mothers of children with trisomy 21 (Down syndrome).

Abstract

Women under 25 years at the birth of a child with trisomy 21 (Down syndrome) appear to have an increased risk of having another child with a trisomy. If the risk of recurrence is due solely to an increased production of trisomic conceptions, women with an affected child should have a rate of spontaneous abortion higher than average, since the majority of aneuploid conceptuses are expected to be aborted. We examined fetal loss rates among the other pregnancies of 545 women delivered of a child with trisomy 21 and compared the observed loss rates with those which would be expected were the relative risk for these women for an aneuploid recognized pregnancy the same as their relative risk for an aneuploid livebirth as reported by others. Overall loss rates in their prior pregnancies were greatest for women who were 20-24 years old at the time of birth of the proband. Moreover, the observed rate of fetal loss for this group of women (33.8%) was at least as high as that predicted from their relative risk for a trisomic livebirth. By contrast, the observed fetal loss rates for women 25-39 years of age at the proband's birth did not differ from the rates predicted on the assumption that their risk for a trisomic recognized pregnancy was not increased, as the livebirth data suggested. The results of this study suggest that women under 25 years at the birth of a child with trisomy 21 have a significantly higher rate of fetal loss in their prior pregnancies than women delivered of the trisomic child at older ages.