European Respiratory Society

Asthma affects time to pregnancy and fertility: a register-based twin study

Elisabeth Juul Gade, SF Thomsen, S Lindenberg, K.O. Kyvik, S Lieberoth, V Backer


Coexistence of infertility and asthma has been observed clinically. We therefore investigated the association between asthma and delayed pregnancy in a nationwide population-based cohort of twins.

A cohort of 15250 twins living in Denmark (aged 12–41 years) participated in a questionnaire study including questions about the presence of asthma and fertility. Differences in time to pregnancy and pregnancy outcome were analysed in subjects with asthma, allergy and in healthy individuals using multiple regression analysis.

Asthma was associated with increased time to pregnancy 27% vs. 21.6%, OR=1.31 (1.1–1.6), p=0.009. The association remained significant after adjustment for age, age at menarche, BMI and socioeconomic status (p=0.05 OR=1.25(1–1.6)), and was more pronounced in those above 30 years of age (32.2% vs. 24.9% p=0.04 OR=1.44 (1.1–1.9)). Untreated asthmatics had significant increased risk of prolonged TTP compared to healthy individuals (OR=1.79 (1.2–2.66) p=0.004), while asthmatics receiving any kind of treatment for asthma trended having a shorter TTP than untreated asthmatics (OR=1.40, p=0.134).

Asthma prolongs time to pregnancy. The negative effect of asthma on fertility increases with age and is growing with disease intensity, indicating that a systemic disease characterized by systemic inflammation also can involve reproductive processes.