asthma inhalerA new study suggests it may take longer for women with asthma to conceive than it does women without the condition. This research adds to mounting evidence that asthma has a negative effect on fertility. The Centers for Disease Control and Prevention says one in 12 adults in the United States has asthma and women are more likely to have asthma than men are.

The study, published in European Respiratory Journal, details how researchers from Bispebjerg University Hospital in Denmark analyzed data from a questionnaire completed by 15,000 twins, aged up to 41 years. The researchers opted to use twin sisters because they could make direct comparisons between the siblings and because using this group allow the researchers to create a sample representation of the entire population without having to measure genetic and lifestyle information for every participant.

This questionnaire included questions on asthma and fertility. Of the 15,000 participants, 955 reported a history of asthma. Analysis of the data shows that 27 percent of women with asthma experienced a delay in pregnancy compared with only 21.6 percent of women without the respiratory condition.

The risk for delay in conception increases greatly in women with untreated asthma. According to study results, 30.5 percent of untreated asthma group showed delays in pregnancy compared with 23.8 percent of those receiving treatment for the condition.

The risk for postponed pregnancy increases with age with women older than 30 years showing a stronger tendency for delayed conception. In the study 32.2 percent of asthmatic women above the age of 30 showed signs of delayed pregnancy while only 24.9 percent of women under the age of 30 had the problem.

Fortunately, women with asthma ultimately have the same number of children as women without the respiratory condition. The study shows the reason for this: women with asthma tend to have children at a younger age than those without it.

In conclusion, the researchers say they assume inflammation associated with asthma was responsible for the delay in pregnancy. The scientists say that women who control their asthma through medication can reduce this delay. Women with asthma can have healthy pregnancies and happy babies.


  • Gade EJ, Thomsen S, Lindenberg S, Kyvik KO, Lieberoth S, Backer V. Asthma affects time to pregnancy and fertility: a register-based twin study. Eur Respir J. 2013 Nov 14.
  • "Asthma's Impact on the Nation, Data from the CDC National Asthma Control Program." Center for Disease Control and Prevention. PDF file. Retrieved 18 Nov 2013.