High blood pressure at entry into antenatal care and birth outcomes among a cohort of HIV-uninfected women and women living with HIV initiating antiretroviral therapy in South Africa

Abstract

Objective: To examine associations between high blood pressure (BP) when entering antenatal care (ANC) and birth outcomes in a cohort of pregnant HIV- and women living with HIV (WLHIV) initiating antiretroviral treatment (ART).

Study design: Prospective cohort study.

Main outcome measures: Cesarean delivery, preterm birth (<37 weeks' gestation), low birthweight (LBW, <2500 g), small-for-gestational age (SGA, <10th percentile), and large-for-gestational age (LGA, >10th percentile for GA).

Results: Of 1116 women (median GA 20 weeks; WLHIV 53%), 48% (53% WLHIV; 43% HIV-) entered ANC with high BP, defined as elevated (120-129 or < 80 mmHg), stage 1 (>130-139 or 80-89) or stage 2 hypertension (≥140 / or ≥ 90). WLHIV were more likely to have high BP (RR 1.32; 95%CI 1.12-1.57), controlling for pre-pregnancy body mass index and additional confounders. In multivariable analysis, there was no evidence that high BP increased the risk of cesarean delivery (RR 1.10, 95% CI 0.92-1.30), preterm birth (RR 1.15, 95% CI 0.81-1.62), LBW (RR 1.16, 95% CI 0.84-1.60) or SGA (RR 1.02, 0.72-1.44), overall or when stratified by HIV-status. High BP was associated with an increased risk of LGA (RR 1.43; 95% CI 1.00-2.03).

Conclusion: In this setting, half of women had high BP at entry into ANC, with WLHIV at increased risk of high BP. There was no strong evidence that high BP increased the risk of adverse birth outcomes overall, or by HIV-status, with the exception of LGA. WLHIV may be at high risk of high BP during pregnancy and should be monitored closely.

Keywords: Birth outcomes; Blood pressure; HIV; Hypertension; Pregnancy; South Africa.

Figure 1.

Study Population of 1,116 live births among HIV-uninfected and women living with HIV initiating ART in South Africa.

Figure 2.. Association between HIV-infection and high blood pressure at enrollment into antenatal care.

Numbers on top of each bar represent the proportion of individuals in that blood pressure category. Blood pressure categorized as: normal (systolic <120 and diastolic <80 mm Hg), elevated (systolic 120–129 and diastolic <80 mm Hg), stage 1 high (systolic 130–139 or diastolic 80–89 mm Hg) or stage 2 hypertension (systolic ≥140 or diastolic ≥90 mm Hg). High blood pressure was defined as elevated, stage 1 or stage 2 hypertension. Hypertensive blood pressure defined as stage 2 hypertension. Effect estimates are adjusted for estimated pre-pregnancy BMI (restricted cubic spline), SES category, maternal age (linear spline), gravidity (linear spline), and alcohol use.

Figure 3.. Proportion of birth outcomes occurring among women in each blood pressure category at entry into antenatal care category.

Women who experienced more than one birth outcome (e.g. SGA and LBW) are included more than once. Preterm: born <37 weeks’ gestation. LBW: low birthweight <2500 grams. SGA: small for gestational age, <10^th percentile for gestational age.