Expectant mothers are commonly advised to relax and avoid stress—often easier said than done during a busy nine months of pregnancy. But a new study led by Tracy Bale, an associate professor of neuroscience in the Department of Animal Biology at the School of Veterinary Medicine, reports that pregnant woman may want to heed this advice and stay stress free.

Together with colleagues, Bale has identified a biological marker of stress in the placentas of mice that appears to impact the brain development of offspring. The same biomarker was found in human placentas and may be part of the mechanism by which maternal stress can increase the risk for neurodevelopmental conditions such as schizophrenia and autism.

Genetics likely play a role in predisposing certain individuals to these conditions, but Bale’s investigations have long probed other sources of risk. Previous studies from her lab have linked factors including a mother’s obesity and stress levels to abnormal outcomes for children. Being male or female also plays a part.

“Neurodevelopmental diseases like autism and schizophrenia have sex biases in their onset and presentation,” says Bale. “It’s possible that males and females start off at different baselines, so insults such as maternal stress impact the developing brain sex-specifically.”

To find a biomarker, or signal of prenatal stress, Bale’s team conducted a search of genes present in the placenta of stressed and unstressed mice during an early stage of pregnancy. One gene, which codes for an enzyme called O-linked-N-acetylglucosamine transferase, or OGT, was suppressed by maternal stress in both males and females compared to unstressed mice, but was much more affected in the males.

When the researchers genetically manipulated levels of placenta OGT, they found mice displayed dramatic differences in the expression patterns of hundreds of genes in the hypothalamus, the portion of the brain responsible for many critical functions including eating, sleeping, and hormone production.

Looking to the future, Bale not only hopes to further study what OGT is doing in the placenta to ultimately affect early brain development, but perhaps also use the protein as a means of assessing an individual’s risk of developing neurodevelopmental disorders such as autism or schizophrenia.

“If we have a marker for stress exposure, we can meld that with what we know about the genetic profiles that predispose individuals to these conditions, and keep a close eye on children who have increased risks,” she says.