If you've got asthma and you're planning a family some time in the future, you may want to move up your timeline a bit: A recent twin study conducted in Denmark revealed that women with asthma, whether treated or not, may not get pregnant as easily as women without the condition.

Researchers at Bispebjerg University Hospital in Copenhagen examined the results of a questionnaire, administered to more than 15,000 twins up to age 41, that included questions about asthma and fertility. While 21.6 percent of the women overall experienced a delay in getting pregnant, 27 percent of those with asthma revealed that they took awhile to conceive. For those twins over age 30, the disparity was even more pronounced—more than 32 percent of over-30 women with asthma experienced a delay in conceiving versus 25 percent of women over 30 who did not have asthma. Women who did not receive treatment for their asthma experienced a significant delay in getting pregnant compared with women who received any kind of treatment for their condition.

The researchers were careful to adjust for maternal age, age at first period, body mass index, and socioeconomic status, but the differences in time to conception remained between those with asthma and those without.

The Inflammation Theory

What does a problem in the respiratory system have to do with reproduction? Some experts believe that because asthma is, at its core, an inflammation of the bronchial tubes, it makes sense that there might be inflammation in other parts of the body such as the fallopian tubes or ovaries. They cite as evidence the fact that women with asthma who take medication get pregnant sooner than those who don't, suggesting that the inflammation tamped down by asthma medication actually is systemic (involves the whole system).

Another possible explanation is that women struggling with asthma simply may not engage in sex as often as others because they aren't feeling well. The Danish study does not say that women with asthma are less likely to conceive, only that it takes them longer to conceive. In fact, at least one study has found that overall fertility rates in women with asthma are the same as those without the condition.

Regardless of when you're planning to start a family, it's imperative that you take steps to manage your asthma now. "While being sure your asthma is well controlled is always important, this study highlights the importance of good control while trying to conceive, and we know that good asthma control during pregnancy is crucial," says Andy Nish, MD, an allergist in Gainesville, Georgia.

Andy Nish, MD, reviewed this article.


Andy Nish, MD, e-mail interview 13 January 2014

National Institutes of Health. "Asthma Affects Time to Pregnancy and Fertility: A Register-Based Twin Study." Web. Accessed 13 January 2014. http://www.ncbi.nlm.nih.gov/pubmed/24232708

Furlow, Bryant, "Respiratory Disease and Fertility are Linked-But Why?" The Lancet
Respiratory Medicine 2(1) (2014), accessed January 15, 2014, doi:10.1016/S2213-2600(13)70241-8.