By PPH Foundation

As climate change drives more frequent, prolonged and intense heat waves across the globe, scientists are increasingly recognising the threat that extreme heat poses to maternal health. For pregnant women, exposure to excessive heat is associated with dehydration, heat stress, preterm labour and pregnancy complications that may increase the risk of postpartum haemorrhage, PPH. Although heat waves do not directly cause PPH, they can trigger physiological changes and obstetric complications that make severe bleeding during and after childbirth more likely. As the climate continues to warm, protecting pregnant women from extreme heat must become an important component of strategies aimed at preventing postpartum haemorrhage and reducing maternal deaths.

Climate change is now recognized by the World Health Organization as one of the greatest threats to human health in the twenty-first century. Pregnant women are among the populations most vulnerable to rising temperatures because pregnancy places additional demands on the cardiovascular and thermoregulatory systems. During pregnancy, women generate more body heat, require increased blood circulation and have a reduced ability to dissipate heat, making them particularly susceptible to heat-related illnesses.

Recent scientific evidence has strengthened concerns about the impact of extreme heat on pregnancy. A comprehensive review published in Nature Medicine in 2024 concluded that exposure to heat waves increases the risks of preterm birth, stillbirth, hypertensive disorders of pregnancy and maternal morbidity. Other studies have shown that prolonged exposure to high temperatures is associated with dehydration, electrolyte imbalance and reduced uteroplacental blood flow, factors that may complicate labour and delivery and contribute to adverse maternal outcomes (Kuehn & Wellenius, 2024).

One important pathway linking heat waves to postpartum haemorrhage is dehydration. During periods of extreme heat, pregnant women lose more fluids through sweating. If these fluids are not adequately replaced, dehydration can reduce circulating blood volume, impair uterine muscle function and contribute to prolonged or dysfunctional labour. Prolonged labour is a recognised risk factor for uterine atony, the leading direct cause of postpartum haemorrhage.

Heat stress may also increase physical exhaustion during labour. Labour requires considerable energy, and women exposed to excessive temperatures may fatigue more quickly, reducing the effectiveness of uterine contractions. Inefficient contractions not only prolong labour but may also compromise the uterus' ability to contract effectively after delivery, increasing the likelihood of excessive bleeding.

Climate change also affects maternal health indirectly by placing enormous pressure on health systems. Heat waves increase electricity demand, raising the risk of power interruptions that can affect maternity theatres, blood storage facilities and cold-chain systems for essential medicines. Water shortages associated with prolonged drought may compromise sanitation and infection prevention in health facilities, while extreme weather events can disrupt transport systems, delaying access to emergency obstetric care when every minute counts.

Evidence from several countries has shown that high ambient temperatures are associated with increased hospital admissions for pregnancy-related complications. A large international study published in The Lancet Planetary Health found that exposure to extreme heat significantly increased adverse maternal and perinatal outcomes, particularly among women living in low-resource settings where adaptive measures are limited. These findings are especially relevant for many African countries, including Kenya, where climate change is increasing the frequency of heat extremes while health systems continue to face resource constraints.

According to Prof. Julius Ogeng'o, Co-Lead of the End Postpartum Haemorrhage Initiative, climate change should now be recognized as an emerging maternal health challenge that demands action beyond the health sector.

"Climate change is no longer only an environmental issue—it is a maternal health issue. Rising temperatures expose pregnant women to physiological stress that may increase the likelihood of pregnancy complications associated with postpartum haemorrhage. Protecting mothers therefore requires climate-responsive health systems that are prepared to manage the growing challenges associated with extreme weather."

He notes that protecting pregnant women begins with awareness and preparedness at both community and health system levels.

"Expectant mothers should be encouraged to stay well hydrated, avoid prolonged exposure to excessive heat where possible, attend all scheduled antenatal care visits and seek immediate medical attention if they experience reduced fetal movements, dizziness, severe headaches or signs of labour during periods of extreme heat. At the same time, health facilities should strengthen emergency preparedness by ensuring reliable power supplies, functional blood storage systems, adequate water supplies and sufficient stocks of medicines used to prevent and manage postpartum haemorrhage."

The World Health Organization continues to recommend evidence-based interventions for preventing postpartum haemorrhage, including the routine administration of uterotonic medicines immediately after birth, timely recognition of excessive bleeding and rapid access to comprehensive emergency obstetric care (World Health Organization, 2023). As climate change increases pressure on health systems, maintaining uninterrupted access to these life-saving interventions becomes even more critical.

Reducing maternal deaths in a changing climate requires looking beyond the delivery room. Climate adaptation strategies should include strengthening maternity services, protecting blood supply systems, improving infrastructure resilience and integrating climate considerations into maternal health planning. While heat waves may be an unavoidable consequence of climate change, the deaths they contribute to, including those from postpartum haemorrhage, are not inevitable. Through early preparation, resilient health systems and evidence-based care, mothers can continue to be protected even as the climate changes.

References

Kuehn, L., & Wellenius, G. A. Climate change and maternal health. Nature Medicine. 2024.

Sun, S., et al. Ambient heat exposure and adverse pregnancy outcomes: A systematic review and meta-analysis. The Lancet Planetary Health. 2023.

World Health Organization. WHO recommendations for the prevention and treatment of postpartum haemorrhage. Geneva: World Health Organization; 2023.

World Health Organization. Climate change and health. Geneva: World Health Organization. 2023.

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