Chromosome studies of embryos from induced abortions in pregnant women age 35 and over.

Chromosome studies of embryos were done in abortions induced at the early stage of pregnancy in women 35 years of age and older who had no signs of threatened or spontaneous abortions and were considered to have oocytes of an advanced age. Karyotypes were successfully determined in 256 cases and the results were as follows: a) 2 of 123 cases in 35- to 39-year-old women showed an incidence of chromosomal anomalies as high as 1.6%; 7 of 117 cases in 40- to 44-year-old mothers an incidence of 6.0%; and 4 of 16 mothers in the 45- to 49-year-old age group an incidence of 25.0%; b) all chromosomal anomalies were trisomies, mainly trisomy 21 and 18. These results suggest that the incidence of chromosomal anomalies increases in older pregnant women, especially in premenopausal pregnancies, and that non-disjunction may occur during meiosis.