Double and triple trisomy in spontaneous abortions: an older maternal age and earlier gestational age than seen in single trisomies

Abstract

It is estimated that as much as 60% of first trimester pregnancy losses are chromosomally abnormal and that single trisomies comprise the majority of these. In comparison, double trisomies are rare and estimated to occur in only 0.21 to 2.8% of karyotyped spontaneous abortions. Pregnancy losses with double trisomies are reported to occur at an earlier gestational age and at an older maternal age than single trisomic losses. From 1992 through 1998 our cytogenetics laboratory successfully cultured 1757 specimens from products of conception. An abnormal karyotype was revealed in 803 (46%) cases including 433 (62%) single trisomies, 20 (2.5%) double trisomies and 6 (0.7%) triple trisomies. Chromosomes 16, 21 and 22 were most frequently observed in the single trisomies, chromosomes 21 and 14 in double trisomies and chromosome 16 in triple trisomies. While the mean gestational age for pregnancy losses with a single trisomy was 12.3 weeks, double and triple trisomy pregnancies were lost at an earlier gestational age, 8.6 weeks. Mean maternal age for the double and triple trisomies was 38.8, in comparison to the single trisomies in which mean maternal age was 37.3 years. Our data supports that previously reported in the literature for double trisomy. Recurrence risk following a single trisomic pregnancy is approximately 1%. Case control studies are needed to determine recurrence risk following double or triple trisomic pregnancies. A significantly greater recurrence risk than that for single trisomy would have implications for genetic counseling.