MedWire News: Pregnant women with asthma are more likely to give birth to an infant with birth defects if they have an asthma attack during pregnancy, researchers have discovered.

The findings indicate the importance of good asthma control during pregnancy, say Dr Lucie Blais and Dr Amélie Forget, from the University of Montreal in Canada.

The researchers studied the medical charts of 4344 pregnant women with asthma, as well as hospital data on the occurrence of birth defects in their children.

In total, 398 of the children born to the women were found to have at least one birth defect, including 261 with major defects.

The researchers found that women who suffered an asthma attack during the first 3 months of pregnancy were 1.5 times more likely to give birth to a child with birth defects, and 1.3 times more likely to have a child with major defects, than those who did not suffer an asthma attack.

These risks were calculated after the researchers accounted for the presence of other diseases and conditions that might cause physical malformations.

"Asthma exacerbations during the first trimester of pregnancy were found to significantly increase the risk of a congenital malformation," the team summarises in the Journal of Allergy and Clinical Immunology.

Drs Blais and Forget conclude: "This study adds evidence to the necessity of keeping asthma under control during pregnancy to avoid exacerbations."