By Megan Rauscher
Babies born to mothers who are stressed out during pregnancy appear to be increased risk for asthma and allergies, according to a study presented at a medical conference in Toronto.
Stress is like a pollutant that, when "breathed" into the body, may influence not only a mother's immune system, but her unborn baby's as well, Dr. Rosalind Wright, of Brigham and Women's Hospital and Harvard Medical School noted in comments to Reuters Health.
"There is a lot of evidence to support the notion that negative experiences that cause stress get into the body and disrupt immune function," Wright said. This is why people are more likely to catch colds or the flu when they're stressed. And, according to Wright's research, mother's stress during pregnancy can also influence her baby's developing immune system.
Dust mites, pollen, molds, tobacco smoke and other substances in the environment are other identified important factors for asthma and allergies. However, those do not fully explain rising rates of asthma seen in the past, or why there's more asthma in inner city and lower income populations.
This motivated Wright's team to consider stress as another important factor. In a study involving about 1 000 families, they measured pregnant women's stress levels by asking questions covering money and housing problems, relationships and other issues. They also tested the level of dust mite allergens in their homes while pregnant.
The researchers measured levels of IgE - antibodies involved in an allergic response - in umbilical cord blood. Among 387 babies tested thus far, levels were increased among those whose mothers suffered higher level stress compared to mothers with less stress. This was true even when the exposure to dust mites during pregnancy was relatively low.
This suggests that mother's stress during pregnancy magnified the effect of dust exposure on the child's immune system, making it more reactive, Wright explained.
Chronic stress can lead to increased levels of cortisol and adrenalin in the body, both of which interact with the functioning of the immune system, she further explained. "If mom is under chronic stress these changes may be more persistent and can even be transmitted to the baby," Wright said.
"So when the baby is now exposed to increased cortisol from the mother, for example, this may change the way their immune system develops and make them more likely to produce IgE, a potential marker of allergic reactivity, when also exposed to lower levels of dust than would normally stimulate the immune system," Wright added.
Pregnant women need to "try to reduce stress as it may affect their own health as well as their baby," she said.
The children in this study are being followed up to see how many of them develop asthma.
The findings were presented Sunday at the American Thoracic Society's 2008 International Conference in Toronto by Wright's colleague, Dr. Junenette Peters, a postdoctoral fellow at the Harvard School of Public Health.