Women with a reduced ovarian complement may have an increased risk for a child with Down syndrome

Advanced maternal age is the only well-established risk factor for trisomy 21 Down syndrome (DS), but the basis of the maternal-age effect is not know n. In a population-based, case-control study of DS, women who reported surg ical removal of all or part of an ovary or congenital absence of one ovary were significantly more likely to have delivered a child with DS than were women who did not report a reduced ovarian complement (odds ratio 9.61; 35% confidence interval 1.18-446.3). Because others have observed that women w ho have had an ovary removed exhibit elevated levels of FSH and similar hal lmarks of advanced maternal age, our finding suggests that the physiologica l status of the ovary is key to the maternal-age effect. In addition, it su ggests that women With a reduced ovarian complement should be offered prena tal diagnosis.