Women with asthma who relied on rescue medications alone while trying to conceive took longer to get pregnant than women without asthma and asthmatic women taking preventive medications, researchers report.
In an analysis of data from the international Screening for Pregnancy Endpoints (SCOPE) study, no significant difference in time to conception was seen among non-asthmatic women and asthmatic women taking inhaled corticosteroids with and without long-acting β-agonists.
But women with asthma using short-acting beta agonist drugs alone took, on average, about 20% longer to conceive and were 30% more likely to take more than a year to get pregnant compared with women without asthma.
Findings from the analysis, published online as a Research Letter in the European Respiratory Journal, suggest that use of preventive medications may protect against impaired fertility, possibly by reducing systemic inflammation, wrote Luke Grzeskowiak, PhD, of the University of Adelaide in Australia, and colleagues.
Grzeskowiak told MedPage Today that the findings should reassure women with asthma who are trying to conceive: “A lot of women have concerns about the safety of asthma medications leading into pregnancy, and many stop taking them. We know that poorly controlled asthma during pregnancy is bad for both the mother and her baby, but we haven’t known much about how it affects fertility.”
Participants in the SCOPE study were healthy, nulliparous women recruited between November 2004 and February 2011 in Auckland (New Zealand), Adelaide (Australia), Cork (Ireland), and Manchester and London (United Kingdom).
Asthma was self-reported, and asthmatic women were further divided by asthma symptoms and asthma medication use. They were also classified as having former asthma (i.e., doctor-diagnosed asthma, no symptoms in the previous 12 months, and no use of asthma medications) or current asthma (doctor-diagnosed asthma, symptoms in the previous 12 months, or use of asthma reliever or prevention medications).
Women with current asthma were further divided according to use of intermittent reliever medications only (i.e., short-acting β-agonists (SABA) or additional use of reliever medications (i.e., inhaled corticosteroids (ICS) with or without long-acting β-agonists (LABA). This resulted in three asthmatic subgroups: former asthma, SABA, and ICS±LABA.
Self-reported time to pregnancy was defined as the duration of having sex (in months) without contraception before pregnancy. Subfertility was defined as time to pregnancy of more than 12 months.
Close to 20% of the 5,617 study participants reported doctor-diagnosed asthma, and 656 (11.75) were identified as current asthmatics.
Among the main study findings:
- Compared with non-asthmatics, current asthmatics managed with SABAs had adjusted fecundity odds radios (FORs) that were 15% lower (0.85, 95% CI, 0.75-0.96); no difference was observed for former asthmatics or current asthmatics using ICS+LABA
- Point estimates for subfertility were increased among women using SABAs (adjusted OR, 1.30, 95% CI 0.93-1.81), but not for women with previous asthma or current asthma using ICS+LABAs
- Women with asthma who conceived using assisted reproductive technologies also showed delayed fertility if they took SABAs alone
The researchers noted that while the exact mechanism that may drive asthma’s impact on fertility remains unknown, “it has been hypothesized that asthma reduces uterine blood supply or increases infiltration of inflammatory cells into the decidua (the uterine mucosal layer), which impairs implantation.”
In a 2015 study of Danish women undergoing infertility treatment, asthmatic women showed reduced vascular endothelial growth factor in uterine endometrial secretion, compared with non-asthmatic women. The researchers speculated that this could affect endometrium receptiveness, thereby increasing the time to conception.
A strength of the study, the researchers said, was its large size, with a relatively large number of women with asthma. Limitations cited included the self-reported nature of asthma and medication use during a single time point (15 weeks gestation), and the absence of data on asthma control and lung function during pregnancy. In addition, the recruitment of only nulliparous women makes generalizability of the findings to multiparous women uncertain.
The researchers reported having no relevant relationships with industry related to the study.