Washington, June 23 (IANS): Stress during the first trimester of pregnancy alters the population of microbes living in a mother's vagina and impact the babies' gut microbiome and brain development, a study shows.

During a vaginal birth, a newborn is exposed to its mother's vaginal microbes, known as microbiota, which colonise the newborn's gut, helping its immune system mature and influencing its metabolism.

"Mom's stress during pregnancy can impact her offspring's development, including the brain, through changes in the vaginal microbiome that are passed on during vaginal birth," said Tracy Bale, senior author and professor of neuroscience in the University of Pennsylvania.

"Babies born by C-section miss out on this initial exposure and are more likely to be exposed to the local environment."

These changes could put the offspring at an increased risk of neurodevelopment disorders such as autism and schizophrenia.

For the study, a group of pregnant mice were periodically exposed to stressors such as predator odours, restraint and novel noises, early in gestation, the equivalent of their 'first trimester.'

The day following birth, the team assessed the microbiota from the mothers' vaginas and from the offsprings' colons.

In addition, the offsprings' brains were examined to measure transport of amino acids, a proxy for brain metabolism and development.

Bale's team found that stress during early pregnancy had surprising long-lasting effects on the mother's vaginal microbiota.

"Many countries are already administering oral application of vaginal lavages to C-section delivered babies to ensure appropriate microbial exposure occurs. Knowledge of how maternal experiences such as stress during pregnancy can alter the vaginal microbiome is critical in determination of at-risk populations," Bale said.

The study appeared in the journal of Endocrinology.