High temperature exposure during pregnancy impacts stress molecules: Study

An exposure to high temperatures during pregnancy could be disrupting amino acids and vitamins key to managing stress and energy, thereby increasing the risk of a premature delivery, suggests an analysis of blood samples.

Studies have observed a link between warmer ambient temperatures and preterm births, where a baby is born before 37 weeks of pregnancy.

The analysis, published in the journal Science Advances, looked at small molecules or "molecular fingerprints" in blood samples of 215 pregnant women who were residents of the US metropolitan city of Atlanta, and matched residential addresses with the maximum ambient temperatures experienced throughout their pregnancies.

The first-of-its-kind study by researchers at Emory University found a disruption in levels of naturally occurring substances in blood, such as methionine, proline, citrulline and pipecolate, when ambient temperatures were higher.

Methionine is an essential amino acid, obtained through diet, while citrulline is a metabolite produced as part of the body's urea cycle. Pipecolate is found in the liver and is involved in how the body responds to oxidative stress.

"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," lead author Donghai Liang, associate professor of environmental health at Emory University's school of public health, said.

"And these same kinds of changes were also seen in those mothers who gave birth prematurely," Liang said.

Evidence from previous studies have suggested that warmer weather conditions can impact biological processes such as production of oxidative stress, heart function and inflammation, the researchers said.

However, the analysis is the first to pinpoint potential molecules and pathways associated with heat and premature birth outcomes, they added.

The authors "identified 23 metabolic pathways and four overlapping metabolites, including methionine, proline, citrulline, and pipecolate, associated with both temperature exposure and PTB (preterm birth). These metabolites are involved in amino acid metabolism and oxidative stress regulation."  "Findings highlight the potential of metabolomics to detect early biological alterations linked to environmental risk and adverse birth outcomes," they wrote.

Every 1 degree Celsius increase in the average daily maximum ambient temperature between conception and early pregnancy was found to be associated with higher levels of methionine, while that between conception and late pregnancy was associated with lower levels of citrulline, pipecolate, and proline.

"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 said.

Data for the analysis was taken from the 'Atlanta African American Maternal-Child Cohort' study that started in 2014.