Chromosome studies in selected spontaneous abortions. 1. Conception after oral contraceptives.

Fifty-four abortuses from women who conceived within six months of discontinuing oral contraceptives were collected over a 2(1/2)-year period. Chromosome analysis of the abortuses showed an increase in triploidy which was highly significant statistically when compared with a control series. Triploidy is virtually always lethal early in embryonic life. Tetraploidy was also increased, but the numbers were too small for analysis. The chromosome disorders which are compatible with livebirth (trisomy and X-monosomy) were not increased in the post-oral-contraceptive abortuses. It is suggested that there is a temporary hormonal imbalance in some women after they discontinue oral contraceptives. This could affect the timing of fertilization. Triploidy could arise at the first or second meiotic division of the ovum or at fertilization. Abortuses are a valuable source of information relating to congenital defects.