Abstract
A cytogenetic investigation was made with induced-aborted conceptuses in order to clarify the frequency of gross chromosome aberrations in the early stage of pregnancy. Samples were limited to those aborted within three months of gestation and were taken only abortions induced for socio-economic reasons. Embryos and the choroinic villi were both examined by the direct method. The fluorescent staining method was used to identify the Y-body for sex determination. Of the 1, 661 cases observed, chromosome analyses were successful in 1, 250 cases (75.3%). The mean maternal age was 28.0 (min. 17-max. 46) years, and the mean gestational age was 8.4±1.39 weeks (mean±S.D.).
Eighty chromosome anomalies were detected (6.4%). The incidence increased as the maternal age advanced. Aneuploidies, polyploidies and structural abnormalities were found in 64 cases (5.1%), 14 cases (1.1%) and 2 cases (0.2%), respectively. In the distribution of trisomies, the maternal age-dependence was distinctive. In monosomies and polyploidies, however, this phenomenon was not observed. The incidence of chromosome anomalies decreased in proportion to the increase in gestational age.
