A prospective study of pregravid oral contraceptive use and risk of hypertensive disorders of pregnancy.

Oral contraceptive use is associated with hypertension, dyslipidemias, and insulin resistance, all of which also characterize hypertensive disorders of pregnancy. In this prospective cohort study, the association of oral contraceptive use before pregnancy and the risk of gestational hypertension and preeclampsia was assessed. Between 1991 and 1995, 3973 nulliparous women who reported their first pregnancy lasting > or = 6 months were studied. Pregravid exposures were collected by biennial mailed questionnaires, and cases were confirmed by medical record review. Recent oral contraceptive use was defined as use within 2 years of pregnancy. Proportional hazards analysis was used to adjust for potential confounding variables. During the 4 years of follow-up, 133 (3.3%) women with gestational hypertension and 62 (1.6%) with preeclampsia were identified. Twenty-five percent of women who did not develop these disorders were recent users of oral contraceptives, compared with 19% (p = 0.11) of women who developed gestational hypertension and 30% (p = 0.38) who developed preeclampsia. Mean duration of prior oral contraceptive use was similar for cases and noncases. Compared with never and past users, the multivariate relative risk among recent users for developing gestational hypertension was 0.7 (95% confidence interval (CI), 0.4-1.0) and for preeclampsia was 1.3 (95% CI, 0.8-2.4). Among recent users who had used oral contraceptives for > or = 8 years, the relative risk for gestational hypertension was 0.6 (95% CI, 0.3-1.2) and for preeclampsia was 2.1 (95% CI, 1.1-4.2). When the analysis was restricted to women who had never smoked, the risk for gestational hypertension was 0.2 (95% CI, 0.1-0.9) and for preeclampsia was 4.1 (95% CI, 1.9-8.7). Thus, recent use of oral contraceptives was associated with a reduced risk for developing gestational hypertension. In contrast, there was a suggestion that recent use was associated with an increased risk of developing preeclampsia, but only among women who had used these agents for > or = 8 years.