The largest systematic review of its kind assesses 198 studies across 66 countries for the impact of heat on maternal, fetal, and neonatal health. This landmark study comes as world leaders prepare for COP29. It provides open-access insights that highlight the urgent need for health-focused climate policies.

 

The study, "Systematic review and meta-analysis of heat exposure impacts on maternal, fetal, and neonatal health," was published in Nature Medicine on 5 November.

 

Researchers at the Planetary Health Research Division in the Faculty of Health Sciences at Wits University were among the authors, including the lead author.

 

Heat exposure increases odds of preterm birth

 

With year-on-year record-breaking global temperatures, the health risks for vulnerable populations—especially pregnant women and newborns—are increasingly concerning.

 

The review found that for every 1°C increase in heat exposure, there was a 4% increase in odds of preterm birth across all the studies. During a heat wave, the odds of preterm birth increased by 26%.

 

Similarly, the review found marked increases in other adverse outcomes such as increased risk for gestational diabetes, stillbirths, congenital anomalies and obstetric complications, with increasing exposure to heat.

 

There is limited research on outcomes like antenatal bleeding and cesarean section risks that may be related to heat exposure and could contribute significantly to morbidity and mortality.

 

Professor Matthew Chersich, Executive Director at Wits Planetary Health Research and co-author of the study says, "Our research provides compelling evidence that heat exposure poses severe health risks for pregnant women and their babies, yet these risks are frequently underestimated."

 

About the study

 

The review provides a comprehensive summary of the published literature to date, quantifying the risks and specific periods of susceptibility associated with heat exposure during pregnancy.

 

Researchers conducted a systematic review, the highest level of evidence reviews, combining the findings of various smaller studies. Various methodologies to summarize the data were used, including vote counting, narrative synthesis, summary of effect estimates and meta-analyses.

 

This review is "living," with updates planned every 18–24 months to ensure that new data from this rapidly growing field is integrated to inform understanding of these critical health risks.

 

The urgency of research in climate-health impacts

 

Despite a growing body of literature, research synthesizing the impacts of heat exposure on maternal and neonatal health has been limited. This review aims to bridge this gap, providing insights into how heat exposure increases the risk of maternal, fetal and neonatal outcomes.

 

Dr. Darshnika Lakhoo in the Planetary Health Research Division and lead author of the study says, "This is a pivotal moment for public health and climate action. Protecting the health of pregnant women and newborns must become a priority in our response to climate change. We hope these findings will catalyze change at the policy level, ensuring at-risk populations receive the support they need."