Maternal Hypertension and Fecundability: A Population-Based Cohort Study.

BACKGROUND The association of hypertension and blood pressure control with fecundability among women is not yet elucidated. The purpose of this study was to evaluate the hypothesis that maternal preconception hypertension would be associated with reduced fecundability and that blood pressure control could reduce excess risk. METHODS Using the National Free Preconception Checkup Projects in Guangdong Province, China, 1422 couples whose female partners had been diagnosed with hypertension and 997 703 reference couples whose female partners were without hypertension were included in this prospective cohort study. Fecundability was measured by time to pregnancy (TTP) and infertility (TTP >12 months). RESULTS Compared with women without hypertension, those with controlled hypertension (time ratio, 1.47 [95% CI, 1.24-1.73]) or uncontrolled hypertension (time ratio, 1.59 [95% CI, 1.34-1.90]) were associated with prolonged TTP and increased risk of infertility (relative risk, 1.19 [95% CI, 1.09-1.31]; relative risk, 1.24 [95% CI, 1.14-1.34]). However, using instrumental variable analyses, there was no significant association between blood pressure control and TTP (time ratio, 0.68 [95% CI, 0.34-1.36]; P=0.270) or infertility (relative risk, 0.97 [95% CI, 0.70-1.34]; P=0.849) among women with hypertension. These results were consistent in the propensity score matching and inverse probability of treatment weighting analyses. CONCLUSIONS Maternal hypertension, with or without controlled blood pressure, was independently associated with prolonged TTP and an increased risk of infertility. These findings may provide insights for the implementation of preconception hypertension screening and the design of future trials.