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 o f pregnancy. In this prospective cohort study, the association of oval cont raceptive use before pregnancy and the risk of gestational hypertension and preeclampsia was assessed. Between 1991 and 1995, 3973 nulliparous women w ho reported their first pregnancy lasting greater than or equal to 6 months were studied. Pregravid exposures were collected by biennial mailed questi onnaires, and cases were confirmed by medical record review Recent oral con traceptive use was defined as use within 2 years of pregnancy. Proportional hazards analysis as used to adjust for potential confounding variables. Du ring the 4 years of follow-up, 133 (3.3%) women with gestational hypertensi on and 62 (1.6%) with preeclampsia were identified. Twenty-five percent of women who did not develop these disorders were recent users of oral contrac eptives, compared with 19% (p = 0.12) of women who developed gestational hy pertension and 30% (p = 0.38) who developed preeclampsia. Mean duration of prior oral contraceptive use was similar for cases and noncases. Compared w ith 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 greater than or equal to 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 restr icted 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). T hus, recent use of oral contraceptives was associated with a reduced risk f or developing gestational hypertension. In contrast, there was a suggestion that recent use was associated with an increased risk of developing preecl ampsia, but only among women who had used these agents for greater than or equal to 8 years.