Darshnika Lakhoo of the University of the Witwatersrand and colleagues from 11 countries conducted a systematic review and meta-analysis of 198 studies and concluded that hot weather is associated with an increased risk of complications during pregnancy and childbirth for both mother and child. The studies included in the analysis were conducted in 66 countries, mainly high-income (63.3 percent) and temperate climate zones (40.1 percent). The results were published in the journal Nature Medicine.
Hot weather was found to be associated with an increased risk of preterm birth: the odds ratio (OR) was 1.04 (95 percent confidence interval 1.03–1.06) per degree Celsius and 1.26 (95 percent confidence interval 1.08–1.47) during heat waves. High temperatures also increased the likelihood of stillbirth (OR 1.13; 95 percent confidence interval 0.95–1.34), congenital anomalies (OR 1.48; 95 percent confidence interval 1.16–1.88) and gestational diabetes (OR 1.28; 95 percent confidence interval 1.05–1.74). During heat waves, there was an increased risk of any obstetric complication (OR 1.25; 95% CI 1.09–1.42).