THURSDAY, Feb. 9, 2006 (HealthDay News) -- Pregnant women with asthma who are carrying a female fetus tend to suffer worse asthma symptoms than asthmatic women carrying a male fetus, a new study finds.
Researchers at the Yale University School of Medicine monitored 702 pregnant women in southern New England and collected information on lung function and other factors that might affect the severity of the women's asthma.
Reporting in the February issue of the American Journal of Epidemiology, they found that asthma symptoms worsened in women with either male or female fetuses until about 30 weeks' gestation. After that point, mothers showed improvement in lung function. However, throughout pregnancy, women carrying male fetuses had about 10 percent better lung function than women carrying female fetuses.
"This difference due to [fetal] sex is potentially important but needs to be placed in context of other factors which have a greater impact on the severity of mother's asthma, including inadequate medical management of asthma symptoms, and whether the mother was a smoker or not," study senior author Michael B. Bracken, a professor of epidemiology, said in a prepared statement.
He and his colleagues speculate that testosterone secreted by the male fetuses may relax the mother's bronchial tissue and inhibit response to histamines. On the other hand, certain sex-specific chemicals excreted by female fetuses may aggravate inflammation in pregnant women. More research is needed to determine the validity of these theories, however, the researchers said.
Asthma is one of the most common diseases associated with pregnancy.
More information
The American Academy of Allergy, Asthma, and Immunology has more about pregnancy and asthma.
