Chromosomal studies on 934 induced abortuses of middle-aged pregnant women.

A total of 934 induced abortuses of middle-aged pregnant women (35–48 years old) were chromosomally surveyed. The mean gestational age was 7.6±2.0 (S.D.) weeks after the first day of the last menstrual period, and the mean maternal age was 39.6±2.7 (S.D.) years. There was a high incidence of chromosomally abnormal fetuses in induced abortions, which markedly increased with the advancing age of the women: 9.6% (40/418) for the 35–39-year-old age group, 20.7% (100/484) for the 40–44-year-old age group, and 43.8% (14/32) for the 45–48-year-old age group, averaging 16.5%.