Study finds heat exposure in pregnancy alters maternal biology linked to preterm birth.

The research analysed blood samples from 215 pregnant women in metropolitan Atlanta, matching their residential addresses with maximum temperatures experienced throughout their pregnancies to identify molecular changes associated with both heat exposure and preterm delivery.

Preterm birth, defined as delivery before 37 weeks of pregnancy, is a leading cause of infant illness and death. While previous research has observed increased premature births during hotter weather, the biological mechanisms behind this link remained unknown until now.

Researchers from Emory University’s Rollins School of Public Health and School of Medicine discovered that higher temperatures disrupt several naturally occurring substances in mothers’ blood, including amino acids and vitamins such as methionine, proline, citrulline and pipecolate. These compounds help the body manage stress and produce energy.

The molecular analysis revealed that heat exposure affects the same biological pathways that are disrupted in mothers who deliver prematurely, suggesting that temperature-related strain may directly increase preterm delivery risk.

“As temperatures have increased, we’ve observed an increased association between more babies being born preterm after the weather was hotter, but scientists still don’t know what exactly is happening in the body-and we really need to understand this to develop effective ways to protect mothers and babies.” said Dr Donghai Liang, associate professor of environmental health at Rollins and the study’s lead author.

The research used metabolomic technology to examine small molecules in the blood, described as “molecular fingerprints” that show how the body responds to environmental stressors.

“We used the innovative metabolomic technology to specifically focus on the small molecules, or ‘molecular fingerprints’ as we call it, and learned for the first time that when the weather was hotter, the mothers’ blood shows some measurable changes in several important molecules and pathways that manage how the body deals with stress or makes energy. And these same kinds of changes were also seen in those mothers who gave birth prematurely.” said Liang.

Previous evidence had suggested that hotter weather affected biological factors including oxidative stress, heart and vascular issues, inflammation and premature rupture of membranes. This study was the first to identify the specific molecules and pathways connecting heat exposure with premature birth outcomes, according to the authors.

The findings could have implications for maternal healthcare as climate change drives global temperatures higher. Identifying these metabolic pathways could enable development of early biomarkers to flag high-risk pregnancies.

By identifying these shared metabolic pathways between hotter temperatures and preterm births, this study could open the door to developing early biomarkers that could help identify pregnancies at higher risk and potentially inform prevention strategies or clinical interventions to support healthier pregnancies.” said Liang.

The research team analysed pregnancies that ended in either full-term or preterm live births, comparing the biological markers in mothers’ blood samples with temperature data from their residential locations throughout pregnancy. This approach established a molecular-level connection between environmental heat exposure and pregnancy outcomes, the authors reported.

Structured infection prevention and treatment cuts maternal deaths and severe complications by nearly one-third, a trial in 59 hospitals has found.

The APT-Sepsis intervention, tested on more than 430,000 women in Malawi and Uganda, showed that systematic improvements in hygiene, infection management and sepsis care reduced maternal mortality in low-resource settings.

Maternal sepsis, a life-threatening response to infection that causes organ dysfunction, kills one mother every 30 minutes globally.

The burden falls heaviest on women in low and middle-income countries where healthcare resources are limited.

The Active Prevention and Treatment of Maternal Sepsis programme, developed by researchers at the University of Liverpool, the World Health Organization and the UN’s Special Programme in Human Reproduction, focused on three key areas: improving hand hygiene compliance, strengthening infection prevention practices, and implementing the FAST-M sepsis bundle for rapid treatment.

The FAST-M bundle provides a structured approach to sepsis care: fluids for resuscitation, antibiotics to fight infection, source control to address the infection’s origin, transfer to appropriate facilities when needed, and continuous monitoring of the patient’s condition.

Results showed the intervention’s effectiveness increased over time, achieving a 47 per cent reduction in infection-related deaths and complications by the final month of the trial.#

The programme proved equally effective in both participating countries and required no costly additional resources beyond training and protocol implementation.

David Lissauer is NIHR professor of global maternal and foetal health at the University of Liverpool.

The researcher said: “These results are hugely significant.

“For too long, maternal sepsis has been a leading but neglected cause of preventable maternal deaths worldwide.

“Our findings demonstrate that APT-Sepsis provides a practical, sustainable, and effective solution.

“With a 32 per cent reduction in infection-related maternal deaths and life-threatening complications, this programme has the potential to transform care.

“Policymakers now have compelling evidence to scale up these interventions so that fewer women die from preventable infections during pregnancy and childbirth.

The programme achieved its results by supporting healthcare workers to adopt evidence-based practices within existing health systems.

Staff received training on hand hygiene standards, infection prevention protocols, and early sepsis detection methods.

Jeremy Farrar, assistant director-general at WHO, emphasised the broader implications: “The APT-Sepsis programme is a testament to what can be achieved when science, policy and frontline care come together.

“Reducing maternal infections and deaths by over 30 per cent is not just a clinical success – it’s a call to action for global health systems to prioritise infection prevention in maternal care.

“We must ensure these life-saving practices are scaled and sustained across all settings.”