Reproductive failure and parental chromosome abnormalities.

The effect of ascertaining on estimates of the frequency of parental chromosome abnormalities in couples with a previous history of pregnancy wastage was investigated by comparing three samples which differ in the ascertainment modality but not in the cytogenetical approach. The incidence of chromosome abnormalities was higher in the sample of 441 couples selected essentially on clinical criteria (6%) than in the two samples (659 and 479 couples) selected retrospectively from the files of two cytogenetic laboratories (4.6 and 3.2%). The comparison of these results with similar data, based on large samples reported in the literature, indicated that sample size may be relevant in producing the wide ranges of variation of the frequency of chromosomal abnormalities. Using our data and those from three other samples of greater than 300 couples a reasonable estimate of the overall incidence of chromosomal abnormalities in couples with a previous history of fetal wastage is approximately 5%.