Defining the risk profile of women with stage 1 hypertension: A time to event analysis

BACKGROUND Chronic hypertension complicates up to 5% of pregnancies and is increasing in prevalence. Women with hypertension have increased risks of serious maternal morbidity and mortality in pregnancy including the development of preeclampsia. In 2017, new guidelines reclassified blood pressure into four categories: normal ( 140/>90 mmHg). This new classification doubles the number of reproductive aged women with hypertension. Furthermore, studies have demonstrated that women entering pregnancy with stage 1 hypertension have an increased risk of developing hypertensive disorders of pregnancy compared to their normotensive counterparts but the time course to development of hypertensive disorder of pregnancy in these women remains uncertain. OBJECTIVE We sought to evaluate the risk of developing a hypertensive disorder of pregnancy and the time to development of these disorders in women with stage 1 hypertension compared to both normotensive women and those with stage 2 hypertension. STUDY DESIGN This is a retrospective cohort study of all patients from a single tertiary care center with singleton gestations from 2014 to 2016. Blood pressure at prenatal visits prior to 20 weeks patients classified into 3 groups: normotensive (<130/80 mmHg), stage 1 hypertension (130-139/80-89 mmHg), or stage 2 hypertension (≥ 140/90 or a history of chronic hypertension). The primary outcome, time to development of a hypertensive disorder of pregnancy was compared between groups was compared using Kaplan Meier curves and log-rank test. Cox proportion hazard models were used to adjust for age, race/ethnicity, pregestational diabetes, and body mass index. Multiple secondary obstetric, maternal, and neonatal outcomes were also assessed. RESULTS Of the 3,000 women in our cohort, 2,370 (79.0%) were classified as normotensive, 315 (10.5%) were classified as stage 1 hypertension, and 315 (10.5%) were classified as stage 2 hypertension. The gestational age at diagnosis was significantly earlier in gestation across blood pressure groups (normotensive 38.7 [37.0, 39.7], vs stage 1 hypertension 38.0 [36.4, 39.4], vs stage 2 hypertension 36.4 [33.7, 37.8]; p<0.001). When the analysis was restricted to only those patients diagnosed with preeclampsia with severe features the same findings were observed. Women with stage 1 hypertension exhibited a 2-fold increased risk of developing hypertensive disorders of pregnancy compared to normotensive women. When compared to stage 2 hypertension women with stage 1 hypertension exhibited a more mild phenotype of hypertensive disorders of pregnancy and exhibited significantly less risk of maternal and neonatal morbidities. CONCLUSIONS Women with stage 1 hypertension are at increased risk of developing hypertensive disorders of pregnancy at earlier gestational ages compared to normotensive women, however, their development of a hypertensive disorder of pregnancy is skewed towards milder disease than women with stage 2 hypertension. These new insights into the graded risk profile of obstetric hypertensive disease associated with new blood pressure categories can better inform our antepartum counseling and monitoring and surveillance plans near term and in the postpartum period.