High heat during pregnancy may disrupt key molecules, raising risk of preterm birth

New evidence suggests that exposure to high temperatures during pregnancy can trigger subtle but significant biochemical changes in the body – changes that may increase the likelihood of preterm birth.

Scientists have found that heat stress may interfere with amino acids and metabolites crucial for managing oxidative stress, maintaining energy balance, and supporting healthy fetal development. These small molecules act as the body’s regulators, helping mothers cope with physical strain and environmental changes.

Among the key molecules affected are methionine, proline, citrulline, and pipecolate.

Methionine is an essential amino acid that supports cellular repair and antioxidant defences. Elevated levels may signal an altered metabolic response to heat.

Citrulline plays a central role in the urea cycle, helping remove ammonia from the body. Lower levels can indicate compromised metabolic efficiency.

Proline, important for tissue growth and collagen formation, also contributes to the body’s stress response.

Pipecolate, produced in the liver, helps regulate oxidative stress – an imbalance here can heighten vulnerability to inflammation.

These molecules form part of 23 metabolic pathways that appear to shift when temperatures rise. Many of these pathways are directly linked to how the body handles stress, produces energy, and maintains a stable internal environment – all critical during pregnancy.

Disruptions in these systems can make the body more vulnerable, creating conditions that may increase the risk of delivering before 37 weeks.

Earlier research has shown that hotter weather can worsen oxidative stress, inflammation, cardiovascular strain, and hormonal balance. But this new analysis is the first to pinpoint specific molecular fingerprints that connect heat exposure to early biological changes tied to preterm birth.

The study behind these insights, published in Science Advances, analysed blood samples from 215 pregnant women in Atlanta, US. Conducted by researchers at Emory University, the work linked daily maximum temperatures during pregnancy with measurable shifts in key metabolites.

Notably, higher temperatures early in pregnancy were associated with increased methionine, while heat exposure later in pregnancy corresponded with lower citrulline, proline, and pipecolate levels.

The findings come from the Atlanta African American Maternal-Child Cohort, an ongoing project that began in 2014.