Ambient temperature during pregnancy and risk of maternal hypertensive disorders: a time-to-event study in Johannesburg, South Africa

BACKGROUND AND AIM: Hypertensive disorders in pregnancy are a leading cause of maternal and perinatal mortality. We evaluate the effects ambient temperature on risk hypertensive throughout pregnancy. METHODS: used birth register data for all singleton births (22-43 weeks’ gestation) recorded at tertiary-level hospital Johannesburg, South Africa, between July 2017-June 2018. Time-to-event analysis was combined with distributed lag non-linear models to examine mean weekly temperature, from conception birth, (i) high blood pressure, hypertension, or gestational (ii) pre-eclampsia, eclampsia, HELLP (hemolysis, elevated liver enzymes, low platelets). Low temperatures were defined as 5th 95th percentiles daily respectively. RESULTS: Of 7986 women included, 844 (10.6%) had disorder which 432 (51.2%) pressure/hypertension/gestational hypertension 412 (48.8%) pre-eclampsia/eclampsia/HELLP. High early associated an increased (23°C vs 18°C) third fourth weeks posed greatest risk, hazard ratios 1.76 (95% CI 1.12-2.78) 1.79 (1.19-2.71), mid-late tended protect against (11°C) during trimester (from 29 however strength statistical significance reduced model adjustments. CONCULSIONS: Our findings support hypothesis that increase severe disorders, likely through effect placental development. This highlights need greater awareness around impacts moderately targeted advice, interventions reduce heat exposure among pregnant women. The potential ameliorating requires further exploration.