PT - JOURNAL ARTICLE AU - Elisabeth J. Gade AU - Simon F. Thomsen AU - Svend Lindenberg AU - Kirsten O. Kyvik AU - Sofie Lieberoth AU - Vibeke Backer TI - Asthma affects time to pregnancy and fertility: a register-based twin study AID - 10.1183/09031936.00148713 DP - 2014 Apr 01 TA - European Respiratory Journal PG - 1077--1085 VI - 43 IP - 4 4099 - http://erj.ersjournals.com/content/43/4/1077.short 4100 - http://erj.ersjournals.com/content/43/4/1077.full SO - Eur Respir J2014 Apr 01; 43 AB - Coexistence of infertility and asthma has been observed clinically. Therefore, we investigated the association between asthma and delayed pregnancy in a nationwide population-based cohort of twins. A cohort of 15 250 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 an increased time to pregnancy, the percentage of asthmatics with a time to pregnancy >1 year was 27% versus 21.6% for non-asthmatics (OR (95% CI) 1.31 (1.1–1.6); p=0.009). The association remained significant after adjustment for age, age at menarche, body mass index and socioeconomic status (OR (95% CI) 1.25 (1.0–1.6); p=0.05), and was more pronounced in those >30 years of age (32.2% versus 24.9%, OR (95% CI) 1.44 (1.1–1.9); p=0.04). Untreated asthmatics had a significant increased risk of prolonged time to pregnancy compared to healthy individuals (OR (95% CI) 1.79 (1.20–2.66); p=0.004), while asthmatics receiving any kind of treatment for asthma tended to have a shorter time to pregnancy 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 with disease intensity, indicating that a systemic disease characterised by systemic inflammation also can involve reproductive processes. Asthma prolongs time to pregnancy: the negative effect of asthma on fertility increases with age and disease intensity http://ow.ly/qpa9B