Perinatal outcomes in women with elevated blood pressure and stage 1 hypertension

Hypertension was redefined in 2017 with lower diagnostic thresholds; elevated blood pressure is defined as systolic blood pressure of 120 to 129 mm Hg with diastolic blood pressure of <80 mm Hg and stage 1 hypertension as systolic blood pressure of 130 to 139 mm Hg or diastolic blood pressure of 80 to 89 mm Hg. These guidelines did not include pregnant women. There is limited information on stage 1 hypertension and pregnancy outcomes.

This study aimed to determine whether elevated blood pressure and stage 1 hypertension as newly defined by the 2017 American College of Cardiology and the American Heart Association guidelines are associated with an increased risk of hypertensive disorders of pregnancy and other adverse maternal and neonatal outcomes.

In this retrospective cohort study, 18,801 women with singletons from 2013 to 2019 were categorized as normotensive, prehypertensive (elevated blood pressure), stage 1 hypertensive, or chronic hypertensive. Women with ≥2 systolic blood pressures of 120 to 129 mm Hg before 20 weeks' gestation were classified into the elevated blood pressure group. Women with ≥2 systolic blood pressures of 130 to 139 mm Hg or ≥2 diastolic blood pressures of 80 to 89 mm Hg before 20 weeks' gestation were assigned to the stage 1 hypertension group. Women were classified as chronic hypertensives if they had any of the following: ≥2 systolic blood pressure of ≥140 mm Hg or ≥2 diastolic blood pressure of ≥90 mm Hg before 20 weeks' gestation, a history of chronic hypertension, or antihypertensive medication use before 20 weeks' gestation. Women with pregestational diabetes, lupus, or <2 blood pressures before 20 weeks' gestation were excluded. The association of stage 1 hypertension with the risk of developing hypertensive disorders of pregnancy was estimated using multivariate logistic regression controlling for maternal sociodemographic characteristics, gestational weight gain by prepregnancy body mass index, parity, and aspirin use. Secondary outcomes included subgroups of hypertensive disorders (gestational hypertension, preeclampsia, eclampsia, and hemolysis, elevated liver enzymes, and low platelet count syndrome), gestational diabetes, placental abruption, intrauterine growth restriction, preterm birth, neonatal intensive care unit admission, stillbirth and neonatal death, and maternal intensive care unit admission. All outcomes were adjusted for potential confounders.

Of the 18,801 women, 13,478 (71.7%) were normotensive, 2659 (14.1%) had elevated blood pressure, 1384 (7.4%) were stage 1 hypertensive, and 1280 (6.8%) were chronic hypertensive. A dose-response relationship was observed: the risk of hypertensive disorders of pregnancy increased from 4.2% in normotensive women to 6.7% (adjusted odds ratio, 1.50; 95% confidence interval, 1.26-1.79) in women with elevated blood pressure, to 10.9% (adjusted odds ratio, 2.54; 95% confidence interval, 2.09-3.08) in women with stage 1 hypertension, and 28.4% (adjusted odds ratio, 7.14; 95% confidence interval, 6.06-8.40) in women with chronic hypertension. Compared with normotensive women, women with stage 1 hypertension had an increased risk of neonatal intensive care unit admissions (15.8% vs 13.0%; adjusted odds ratio, 1.21; 95% confidence interval, 1.03-1.42), preterm birth at <37 weeks' gestation (7.2% vs 5.2%; adjusted odds ratio, 1.45; 95% confidence interval, 1.16-1.81), and gestational diabetes (14.8% vs 6.8%; adjusted odds ratio, 2.68; 95% confidence interval, 2.27-3.17).

Our study demonstrates that elevated blood pressure and stage 1 hypertension, using the 2017 American College of Cardiology and the American Heart Association guideline definition, are associated with increased maternal and neonatal risk. This group of women warrants further investigation to determine whether pregnancy management can be altered to reduce maternal and neonatal morbidity.