Preconception blood pressure and risk of gestational hypertension and preeclampsia: a large cohort study in China

Our objective was to examine whether high blood pressure in the preconception period was associated with gestational hypertension and preeclampsia in Chinese women. Data were obtained from the China-US Collaborative Project for Neural Tube Defects Prevention, a large population-based cohort study. We included 45,628 women who were registered before pregnancy in seven counties in South China. Blood pressure was measured during registration by trained health care workers, and other health-related information was recorded prospectively. We used logistic regression to evaluate the associations between preconception blood pressure and the risk of gestational hypertension and preeclampsia, adjusting for potential confounders. The prevalence of hypertension in the preconception study population was 4.57% (2083/45,628). The incidences of gestational hypertension and preeclampsia were 11.95% and 4.08%, respectively, in the hypertension group and 8.60% and 2.28%, respectively, in the nonhypertension group. Compared with the nonhypertension group, the hypertension group showed a significantly increased risk for gestational hypertension [adjusted risk ratio (RR) = 1.40, 95% confidence interval (CI): 1.22-1.60] and preeclampsia [adjusted RR = 1.75, 95% CI: 1.39-2.19]. When participants with normal blood pressure were used as the reference, the adjusted ORs for gestational hypertension were 1.48 (95% CI: 1.37-1.59), 1.70 (95% CI: 1.44-2.01), and 1.29 (95% CI: 1.02-1.64), and for preeclampsia, the adjusted ORs were 1.55 (95% CI: 1.35-1.78), 1.95 (95% CI: 1.46-2.60), and 1.99 (95% CI: 1.39-2.85) for the participants with prehypertension, stage 1 hypertension, and stage 2 hypertension, respectively. Our results support an association between hypertension or higher blood pressure prior to pregnancy and an increased risk of gestational hypertension and preeclampsia.