In those women not taking the pill, the study found that increased levels of estrogen were associated with decreased airway inflammation, and that increased levels of progesterone show increased inflation in the airway.
However, those women on birth control, which lessens hormone fluctuations, showed no differences throughout the month.
"This study is a first step in looking at the relationship between hormones and asthma," said Dr. Piush Mandhane, from the University of Alberta in Canada. "Hormones do play a role, and women need to be aware that there's a potential relationship between their asthma symptoms and their menstrual cycles."
The findings may help doctors better manage asthma among pre-menopausal women.