Hot weather linked to pre-term birth risk

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.