An Emory University study, published Friday by Science Advances, provides the first evidence that exposure to higher temperatures during pregnancy is linked to specific biological changes in mothers that are also associated with preterm birth.

A team of researchers from Emory University's Rollins School of Public Health and School of Medicine conducted a novel molecular analysis of blood samples from 215 pregnant women living in metropolitan Atlanta, whose pregnancies ended in either full-term or pre-term live births (delivery before 37 weeks of pregnancy), and then matched the mothers' residential addresses with the maximum ambient temperature experienced throughout their pregnancies.

This first-of-its-kind analysis found that several naturally occurring substances, such as methionine, proline, citrulline, and pipecolate, are disrupted when temperatures are higher. These amino acids and vitamins play key roles in managing stress and energy in the body, suggesting that heat-related biological strain may increase the risk of preterm delivery.

Previous scientific evidence suggested hotter weather impacted biological factors such as oxidative stress, heart and vascular issues, inflammation, and the premature rupture of membranes. However, this was the first study to pinpoint the potential molecules and pathways associated with heat and premature birth outcomes.

"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.

Preterm birth is a leading cause of infant illness and death, but little is known about the biological reasons behind it, especially in relation to environmental stressors.

"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," Liang says.