Fertility outcomes in asthma: a clinical study of 245 women with unexplained infertility

Evidence is increasing of an association between asthma and aspects of female reproduction. However, current knowledge is limited and furthermore relies on questionnaire studies or small populations. In a prospective observational cohort study to investigate whether time to pregnancy, the number of fertility treatments, and the number of successful pregnancies differ significantly between women with unexplained infertility with and without asthma. 245 women with unexplained infertility (aged 23-45 years) underwent questionnaires and asthma and allergy testing while undergoing fertility treatment. 96 women entering the study had either a former doctor's diagnosis of asthma or were diagnosed with asthma when included. After inclusion they were followed for a minimum of 12 months in fertility treatment, until they had a successful pregnancy, stopped treatment, or the observation ended. The likelihood of achieving pregnancy was lower in women with asthma compared with those without asthma: median total time to pregnancy was 32.3 months in non-asthmatic women versus 55.6 months in those with asthma, hazard ratio 0.50 (95% confidence interval 0.34-0.74) p<0.001. Women with asthma had fewer successful pregnancies during fertility treatment, 39.6 versus 60.4% (p=0.002). Increasing age was of negative importance for expected time to pregnancy, especially among asthmatic women (interaction between age and asthma on time to pregnancy, p=0.001). Female asthmatics had a longer time to pregnancy and less often became pregnant than non-asthmatic women. Increasing age reduced the chances of conceiving especially among asthmatic women. The causal relationship between asthma and subfertility remains unclear.