Contraceptives and the conceptus. I. Chromosome abnormalities of the fetus and neonate related to maternal contraceptive history.

The chromosomes of 3080 products of conception, consisting primarily of newborn infants and medically induced abortions, were examined. These were from 3 major groups of women, those who had used oral contraceptives (primarily the combination types), those who had used nonhormonal contraceptives, and a control group of those who had not used any contraceptives. In the newborn study population, the chromosome abnormality rate was 5.4 per 1000 infants (when cases of proven hereditary involvement are excluded the figure drops to 3.6 per 1000), and in the entire induced-abortion study series it was 7.3 per 1000. These rates are very similar to those obtained in other surveys. The rate of chromosomally abnormal conceptuses increases with increasing maternal age in both the newborn and induced-abortion groups. No statistically significant relationships were found between the observed or age-adjusted rates of chromosome abnormalities and contraceptive history (P greater than .10 in all cases). The findings make it clear that the use of oral contraceptives has no large effect on the risk of having a chromosomally abnormal child although the possibility of a small increase or decrease in this risk, of at most about 10 per 1000, cannot be ruled out because of the small number of abnormalities found.