Maternal-age effect in aneuploidy: does altered embryonic selection play a role?

The age of mothers of children with trisomy 21 (47,+21) is elevated no matter if the extra chromosome is of maternal or paternal origin, and it has been postulated that decreasing maternal selection against affected conceptuses with advancing age might explain this observation. Since the absence of sufficient data on 47,+21 abortuses precludes a direct test of this hypothesis, we have taken an indirect approach. Pooled data from spontaneous abortions and live births with autosomal trisomies, XXY and XXX, were examined to determine the natural history of these aneuploid conceptuses and its relation to maternal age. The results are consistent with decreasing embryonic selection in older women.