Blood pressure control in pregnant patients with chronic hypertension and diabetes: should <130/80 be the target?

Abstract

Background: The Chronic Hypertension and Pregnancy Study demonstrated that a target blood pressure of <140/90 mm Hg during pregnancy is associated with improved perinatal outcomes. Outside of pregnancy, pharmacologic therapy for patients with diabetes and hypertension is adjusted to a target blood pressure of <130/80 mm Hg. During pregnancy, patients with both diabetes and chronic hypertension may also benefit from tighter control with a target blood pressure <130/80 mm Hg.

Objective: We compared perinatal outcomes in patients with hypertension and diabetes who achieved blood pressure <130/80 vs 130 to 139/80 to 89 mm Hg.

Study design: This was a secondary analysis of a multcenter randomized controlled trial. Participants were included in this secondary analysis if they had diabetes diagnosed prior to pregnancy or at <20 weeks of gestation and at least 2 recorded blood pressure measurements prior to delivery. Average systolic and diastolic blood pressure were calculated using ambulatory antenatal blood pressures. The primary composite outcome was preeclampsia with severe features, indicated preterm birth <35 weeks, or placental abruption. Secondary outcomes were components of the primary outcome, cesarean delivery, fetal or neonatal death, neonatal intensive care unit admission, and small for gestational age. Comparisons were made between those with an average systolic blood pressure <130 mm Hg and average diastolic blood pressure <80 mm Hg and those with an average systolic blood pressure 130 to 139 mm Hg or diastolic blood pressure 80 to 89 mm Hg using Student's t test and chi-squared tests. Multivariable log-binomial regression models were used to evaluate risk ratios between blood pressure groups for dichotomous outcomes while accounting for baseline covariates.

Results: Of 434 participants included, 150 (34.6%) had an average blood pressure less than 130/80 mm Hg. Participants with an average blood pressure less than 130/80 were more likely to be on antihypertensive medications at the start of pregnancy and more likely to have newly diagnosed diabetes mellitus prior to 20 weeks. Participants with an average blood pressure less than 130/80 mm Hg were less likely to have the primary adverse perinatal outcome (19.3% vs 46.5%, adjusted relative risk 0.43, 95% confidence interval 0.30-0.61, P<.01), with decreased risks specifically of preeclampsia with severe features (adjusted relative risk 0.35, 95% confidence interval 0.23-0.54) and indicated preterm birth prior to 35 weeks (adjusted relative risk 0.44, 95% confidence interval 0.24-0.79). The risk of neonatal intensive care unit admission was lower in the lower blood pressure group (adjusted relative risk 0.74, 95% confidence interval 0.59-0.94). No differences were noted in cesarean delivery (adjusted relative risk 1.04, 95% confidence interval 0.90-1.20), fetal or neonatal death (adjusted relative risk 0.59, 95% confidence interval 0.12-2.92). Small for gestational age less than the 10th percentile was lower in the lower blood pressure group (adjusted relative risk 0.37, 95% confidence interval 0.14-0.96).

Conclusion: In those with chronic hypertension and diabetes prior to 20 weeks, achieving an average goal blood pressure of <130/80 mm Hg may be associated with improved perinatal outcomes.

Keywords: antihypertensives; chronic hypertension; diabetes.