Female Fetus More Likely to Cause Asthma Symptoms in Moms

A study in the February American Journal of Epidemiology finds that pregnant women who are carrying a female fetus are more likely than those carrying a male fetus to experience more severe asthma symptoms.

Researchers from Yale University evaluated 702 pregnant women with asthma and measured lung function for 10 days at “selected points in their pregnancy.” The researchers found that throughout their pregnancies, women carrying male fetuses had 10% better lung function than women carrying female fetuses. Although the researchers are unsure why the sex of the fetus affects asthma and say more research is necessary, they speculate that testosterone secreted by male fetuses “may relax the mother’s airway tissue”.

Read the full article:

Helen L. Kwon, Kathleen Belanger, Theodore R. Holford, and Michael B. Bracken (2006)
Effect of Fetal Sex on Airway Lability in Pregnant Women with Asthma. American Journal of Epidemiology 163: 217-221.