Mothers may pass 'stress patterns' to child via vaginal bacteria and placenta

Two animal studies have shown that pregnant women may transmit the damaging effects of stress to their unborn child by way of the bacteria in their vagina and through the placenta.

Stresses felt by mothers during pregnancy have been shown to affect offspring neurodevelopment and increase the risk for disorders such as autism and schizophrenia, but the mechanisms by which it can reprogram the developing brain are not clear.

As a newborn passes through the birth canal, the microbiome of a mother's vagina ends up in the offspring's gut.

In the first study, the team, led by Tracy L. Bale, PhD, Professor of Neuroscience in the Perelman School of Medicine, Department of Psychiatry and the School of Veterinary Medicine Department of Animal Biology at Penn, found that changes in the microbiome produced by stress in pregnant mice altered the microbe population in the newborn's gut and correlated to changes in the developing brain.

Using targeted approaches in mice, the researchers determined that early prenatal stress affected both the maternal and offspring levels of lactobacillus, a lactic acid-producing bacteria associated with brain neurochemistry.

The team then observed changes in gene expression in the hypothalamus in offspring of the mice that correlated with levels of lactobacillus. Many of these genes play a critical role in development and brain function.

In a parallel animal study, Bale and colleagues were looking for predictive biomarkers of maternal stress and found that a specific protein in the placenta, OGT, may have implications for brain development in offspring. The single enzyme is known as O-linked-N-acetylglucosamine transferase or "OGT," which is important in a wide variety of regulatory functions, including development.

The researchers found that placentas associated with male mouse pups had lower levels of OGT than the placentas associated with female pups, and levels of OGT in the placenta were even lower when their moms were stressed.

The studies were presented at the University of Pennsylvania at Neuroscience 2013.