Stress during pregnancy increases the risk of child developing asthma

New research from the U.S. suggests that women who suffer from stress during pregnancy may increase the risk of their child developing allergies.

Scientists at Harvard Medical School say they have found higher levels of a chemical linked to allergies in the blood of children whose of mothers are stressed.

According to the researchers the levels were high even in those who had not been exposed to recognised allergy triggers such as dust mites.

The researchers conducted a study of 387 babies, and found that babies exposed to stress before birth have an increased tendency to react to allergy triggers and it lends support to the theory that stress may influence the body's immune response.

Dr. Rosalind Wright says it is thought that asthma and allergies are controlled by a complex mix of genetic and environmental factors but it is also suspected that the impact of these factors may in some way be influenced by the environment a foetus is exposed to while still in the uterus.

In order to examine the premise that stress during pregnancy can magnify the effect of foetal exposure to substances which trigger allergies, the Harvard team measured the levels of Immunoglobulin (IgE) - a chemical linked to allergic responses - in the umbilical cord blood of the babies.

As even babies exposed to low levels of dust mites in the uterus displayed elevated levels of IgE, the researchers say that stress was amplifying their allergic response.

Dr. Wright of Brigham & Women's Hospital and Harvard Medical School, says their research adds to a growing body of evidence that links maternal stress, such as that caused by financial problems or relationship issues, to changes in children's developing immune systems, even during pregnancy.

Dr. Wright says it also supports the idea that stress can be thought of as a social pollutant that may influence the body's immune response similar to the effects of physical pollutants like allergens, thus adding to their effects.

The researchers say more research needs to be done to explore the effect of stress from other possible factors which may also influence the allergy risk.

Experts say the link between stress and asthma has long been recognised and the preliminary findings highlight the importance of a healthy and balanced lifestyle during pregnancy.

Dr. Wright says while predisposition to asthma may be, in part, set at birth, the factors that may determine this are not strictly genetic.

Earlier research found that the children of stressed mothers had lower IQs at 18 months and double the risk of hyperactivity and attention deficit hyperactivity disorder at the age of four.

The research was presented at the American Thoracic Society International Conference in Toronto.