Chromosome Abnormalities in 1355 Induced Abortuses

A total of 1536 induced abortuses of less than 12 weeks gestation were cultured and 1355 successfully karyotyped. The study was divided into two periods: in the initial period 1224 abortion specimens were randomly collected, but in the later period 312 specimens of less than 8 weeks gestation or from women over 35 years of age were selectively collected. Eighty-six or 6.3% of the 1355 karyotyped specimens had chromosome abnormalities, and these included 61 trisomics, 9 monosomy X, 7 triploids, 5 double aneuploids, 2 tetraploids, one balanced translocation and one mosaic trisomy 22. Chromosomal abnormality rates by five-year maternal age intervals were 3.4 to 3.6% for women under 34 years of age, 9.3% for women aged 35-39 years and 23.0% for women over 40 years. Factors that may influence the prevalence of abnormal karyotypes in induced abortuses and prenatal selection rates of chromosome abnormalities compatible with livebirth are discussed.