Pregnancy & Asthma

We all know that estrogen and progesterone are critical players in a woman's reproductive process. But could these hormones also improve her breathing? According to a recent report published in the March issue of Annals of Allergy, Asthma & Immunology, there is strong evidence that estrogen and progesterone may actually improve lung function and asthma. Conversely, during periods when hormonal levels are lower than average—menstruation, pregnancy, and menopause—women with asthma may be at increased risk of asthma attacks.

Below, the report's author, Dr. Catherine L. Haggerty of the University of Pittsburgh, Graduate School of Public Health, offers an explanation for these findings and talks about how this information might help women identify high-risk times for asthma attacks.

Can you describe first the basic premise of your report? What are the effects of hormones on respiratory function?
The report looked at the association between estrogen and progesterone and pulmonary function, and asthma among women.

The data suggests that both estrogen and progesterone may be involved in improving pulmonary function and asthma. So in younger women, during the premenstrual and menstrual phases when these hormone levels are lower, asthmatics have been found to experience an increase in asthma attacks, increased hospitalization, decreased pulmonary function and maybe an increased need for medications such as bronchodilators to treat their asthma systems.

Oral contraceptives, which really dampen and smooth out these fluctuations in hormone levels, have been found to improve pulmonary function in some women as well.

Reports of lung function during pregnancy were a bit more mixed. About a third of pregnant women report that their asthma improves during pregnancy. Another third report no change, and the final third report that it actually worsens. But there are other factors that may be affecting pulmonary function in pregnant women such as increase in gastroesophageal reflux and increase in intra-abdominal pressure and all of these things also affect lung function. So it may be that even if estrogen and progesterone have a positive effect, pulmonary function is affected by so many things in pregnancy that that might be the reason for the differences among women.

There is not as much data on menopausal women. I've done some studies on hormone replacement therapy in menopausal women and found that women who take hormone replacement therapy have better pulmonary function and less pulmonary obstruction than women who do not take hormone replacement therapy even after accounting for other factors that may be associated with pulmonary function such as smoking. So even after taking smoking into account, HRT is still associated with better pulmonary function.

Do we know why estrogen and progesterone may improve lung function?
Asthma is characterized by inflammation and narrowing of the airways. This inflammation may occur as a result of a hyperimmunity. So the immune system might be overly revved up. Progesterone has been shown to suppress the immune system and so in that sense it's protective or helpful. It may reduce the increased inflammation that's occurring.

Additionally, both progesterone and estrogen have been found to reduce constriction of the airways and relax the bronchial smooth muscle in the airways. Progesterone is responsible for relaxing uterine smooth muscle—that's its natural function, and it's been found to impart these effects throughout the whole body—so it also works to relax the muscles in the airways.

Who may experience worsening asthma symptoms?
Premenstrual women may notice a worsening of asthma symptoms just before and during the menstrual cycle. This is the time when estrogen and progesterone are at their lowest levels and it's also the time at which they really drop. So certainly women could see if they notice a pattern in asthma related to the menstrual cycle. This could be something they could discuss with their doctor at that time.

Another time to look for changes would be as women move through and into the menopausal period because at this time estrogen, progesterone also rapidly decline.

What is the percentage of women with asthma who have worsening symptoms during their periods?
The majority of the data suggests about a third of the women, but the range is really about a third to a half of women who are specifically asked if they experience worsening of asthma.

Why is this relationship between lung function and hormones important?
Understanding that in a subset of women, asthma may worsen during times of low hormonal levels, we may be able to better predict who is at risk for more frequent asthma attacks, and when. In some women there may be treatment suggestions that could be made based on this information. I don't think at this time we could make any recommendations. But if women discuss these patterns with their doctor, they may find they benefit from using oral contraceptives to smooth out the fluctuations in hormonal levels. And there may be therapeutic strategies that could be developed in the future, which takes advantage of this relationship.