Experts believe mothers who report high stress levels during pregnancy are more likely to have babies who will suffer neurodevelopmental and psychiatric conditions in later life.

A team at the Hebrew University of Jerusalem says perceived prenatal stress (PPS) actually reprograms key molecular pathways in the baby’s body – and has a far more significant effect on girls than boys.

PPS alters the expression of RNA – the tiny molecules that helps make proteins — in the blood of newborn babies, especially girls. That, in turn, affects key enzymes in the brain’s stress-regulation system.

“We found that even before babies take their first breath, the stress their mothers experience can shape how their bodies manage stress themselves,” said Prof. Hermona Soreq, who jointly led the study with PhD student Shani Vaknine Treidel at the university’s Edmond and Lily Safra Center of Brain Science.

The research team says these changes may explain why some children are more vulnerable to developmental or psychiatric challenges – and point to new possibilities for early diagnosis and interventions targeting stress-related health risks.

“This study provides a powerful glimpse into how the maternal environment can leave a lasting biological imprint on the next generation,” said Vaknine Treidel.

“It also underscores the importance of recognizing and supporting mental health during pregnancy — not just for the mother, but for the lifelong health of the child.”

The team used a standard questionnaire to measure perceived stress among women in their third trimester at Klinikum Rechts der Isar Hospital, part of the Technical University of Munich, Germany.

They then analyzed blood from the umbilical of babies born to 120 mothers aged 28 to 45 who recorded some of the highest scores.

The changes they detected in the RNA molecules were sex-specific, they said, and showed more dramatic shifts among newborn girls than boys — which could explain why children exposed to high maternal stress during pregnancy may be more vulnerable to neurodevelopmental and psychiatric conditions later in life.

Using machine learning techniques, the researchers were also able to accurately determine whether or not newborn girls had been exposed to maternal stress based on profiles of small RNA molecules (or tRNA fragments) that govern a neurotransmitter essential for brain function.

This opens the door to new diagnostic tools for detecting prenatal stress effects and possibly even early interventions, the team said.

The research paper was published in the journal Molecular Psychiatry.