Blood pressure trajectory and category and risk of hypertensive disorders of pregnancy in nulliparous women

Abstract

Background: Recently updated American College of Cardiology/ American Heart Association (ACC/AHA) guidelines redefine blood pressure categories as stage 1 hypertension (systolic, 130–139 mm Hg or diastolic, 80–89 mm Hg), elevated (systolic, 120–129 mm Hg and diastolic, <80 mm Hg), and normal (<120/<80 mm Hg), but their relevance to an obstetric population is uncertain. Objective: We sought to evaluate the risk of gestational hypertension or preeclampsia based on early pregnancy blood pressure category and trajectory. Study Design: We utilized data from the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be cohort, a prospective observational study of nulliparous women with singleton pregnancies conducted at 8 clinical sites between 2010 and 2014. Women included in this analysis had no known history of prepregnancy hypertension (blood pressure, ≥140/90 mm Hg) or diabetes. We compared the frequency of hypertensive disorders of pregnancy, including preeclampsia and gestational hypertension, among women based on ACC/AHA blood pressure category at a first-trimester study visit and blood pressure trajectory between study visits in the first and second trimesters. Blood pressure trajectories were categorized based on blood pressure difference between visits 1 and 2 as stable (<5 mm Hg difference), upward (≥5 mm Hg), or downward (≤-5 mm Hg). Associations of blood pressure category and trajectory with preeclampsia and gestational hypertension were assessed via univariate analysis and multinomial logistic regression analysis with covariates identified a priori. Results: A total of 8899 women were included in the analysis. Study visit 1 occurred at a mean gestational age of 11.6 ± 1.5 weeks and study visit 2 at a mean gestational age of 19.0 ± 1.6 weeks. First-trimester blood pressure category was significantly associated with both preeclampsia and gestational hypertension, with increasing blood pressure category associated with a higher risk of all hypertensive disorders of pregnancy. Elevated blood pressure was associated with an adjusted relative risk of 1.54 (95% confidence interval, 1.18–2.02) and stage 1 hypertension was associated with adjusted relative risk of 2.16 (95% confidence interval, 1.31–3.57) of any hypertensive disorder of pregnancy. Stage 1 hypertension was associated with the highest risk of preeclampsia with severe features, with an adjusted relative risk of 2.48 (95% confidence interval, 1.38–8.74). Both systolic and diastolic blood pressure trajectories were also significantly associated with the risk of hypertensive disorders of pregnancy independent of blood pressure category (P