Hypertensive disorders of pregnancy and perinatal outcomes: two prospective cohort studies of nulliparous women in India and Tanzania

Introduction
Hypertensive disorders of pregnancy (HDP) have been linked with increased risk for maternal and offspring complications in high-income settings. However, in resource-limited settings, studies with robust measurement of HDP, including severity and timing, and perinatal outcomes are limited.

Methods
We analysed data from two prospective cohorts of nulliparous women in India (n=10 570 pregnancies) and Tanzania (n=10 299 pregnancies) who were enrolled in calcium supplementation trials and had blood pressure and proteinuria assessments throughout pregnancy and at the time of labour and delivery. Generalised estimating equations were used to assess the relationship between HDP severity categories (gestational hypertension, preeclampsia without severe features and preeclampsia with severe features) and timing of HDP onset (early-onset <34 weeks vs late-onset ≥34 weeks gestation) with adverse perinatal outcomes.

Results
The cumulative incidence of HDP was 3.7% and 4.5% in the India and Tanzania cohorts, respectively. All HDP severity categories were associated with a significantly higher risk for perinatal death in both cohorts (p values<0.05). Pregnancies complicated by pre-eclampsia with severe features had the largest magnitude of increased risk for perinatal death as compared with pregnancies without an HDP (India RR 8.60; 95% CI 5.90 to 12.53; Tanzania RR 4.05; 95% CI 2.91 to 5.66). In both cohorts, pre-eclampsia with and without severe features, but not gestational hypertension, was associated with increased risks for preterm birth and low birth weight. Pregnancies with early-onset HDP had a high absolute risk of perinatal death (India 25.6% and Tanzania 36.9%), and the risk was markedly increased as compared with late-onset HDP (India RR 4.79; 95% CI 2.68 to 8.54; Tanzania RR 5.79; 95% CI 3.56 to 9.41).

Conclusion
HDP were differentially associated with risks for perinatal outcomes by severity and timing of onset. Interventions that prevent, reduce the severity or delay the onset of HDP may improve perinatal outcomes in resource-limited settings.

Trial registration number ClinicalTrials.gov number, NCT03350516