Role of oral contraception in congenital malformations of offspring.

In a case control study we examined the relationship between congenital malformations in offspring and maternal exposure to oral contraceptives around the time of conception. There were 1 370 with congenital malformations and 2 968 healthy control infants. Maternal oral contraceptive use was unrelated to malformations considered as a whole whether exposure last occurred in the year before conception [odds ratio = 0.9, p=0.25] or during pregnancy [odds ratio = 1.3, p=0.30]. Exposure during pregnancy doubled the risk for some specific diagnoses, including certain cardiovascular defects, but these increases were not statistically significant. Exposure to specific oestrogens or progestogens was also unrelated to the occurrence of malformations. There was a suggestion that women who both smoked more than 20 cigarettes per day and used oral contraceptives during pregnancy were more likely to deliver a malformed infant than were women who neither used oral contraceptives nor smoked during pregnancy.