Higher prevalence of hypertensive disorders of pregnancy in women who smoke: the Japan environment and children's study.

Smoking during pregnancy is a risk factor for various adverse birth outcomes but lowers the risk of preeclampsia. Cardiovascular adaptations might underlie these associations. We examined the association of maternal smoking with the risk of hypertensive disorders of pregnancy (HDP) in a low-risk population-based cohort of 76,303 pregnant women. This study was a part of the Japan Environment and Children's Study. Smoking status was assessed using questionnaires completed by participants. Information about HDP was assessed using questionnaires completed by doctors. Compared with that for women who did not smoke, women who continued smoking >10 cigarettes per day during pregnancy had a significantly higher risk of developing HDP (odds ratio: 1.58, 95% confidence interval: 1.11-2.25). In multivariate analyses with adjustment for possible confounding factors, the association still remained (odds ratio: 1.51, 95% confidence interval: 1.04-2.19). When we regarded the number of cigarettes as a continuous variable, there was a linear association between the number of cigarettes and risk of HDP, with an odds ratio of 1.02 per cigarette per day (95% confidence interval: 1.00-1.04). Smoking a greater number of cigarettes was associated with a higher risk of HDP after adjustment for possible confounding factors. Cigarette smoking cessation may avoid the complications of HDP. Our findings suggest that, in addition to the risk of small-for-gestational-age children, an increased risk of HDP should be considered in the management of pregnant women who smoke cigarettes.