Women who suffer stress during their pregnancies are more likely to give birth to children who will suffer from asthma and allergies, according to new research.

Stressed moms-to-be may pass that stress on to their babies in the form of a "social pollutant," according researchers from Harvard Medical School who presented their findings Sunday at the American Thoracic Society’s 2008 International Conference in Toronto.

“While predisposition to asthma may be, in part, set at birth, the factors that may determine this are not strictly genetic," said Dr. Rosalind J. Wright, assistant professor of medicine at Brigham & Women’s Hospital and Harvard Medical School, in a news release.

Researchers studied 387 infants enrolled in the Asthma Coalition on Community, Environment, and Social Stress project in Boston.

They found that stress during pregnancy may also influence the babies’ developing immune systems, increasing fetus exposure to dust and other particles that may lead to asthma, the researchers said. While animal studies have found that the combination of stress and allergen exposure during pregnancy may magnify the effects on the immune system, this is the first human study to examine this directly, the researchers aid.

“This research adds to a growing body of evidence that links maternal stress such as that precipitated by financial problems or relationship issues, to changes in children’s developing immune systems, even during pregnancy,” Wright added. “This further supports the notion that stress can be thought of as a social pollutant that, when ‘breathed’ into the body, may influence the body’s immune response similar to the effects of physical pollutants like allergens, thus adding to their effects.”

Wright said further research is needed in larger test groups to determine the long-term effects of stress in pregnancy.