Fertility treatment among women with asthma: a case-control study of 3689 women with live births.

Asthma has been linked with prolonged time to pregnancy. Our aim was to explore a possible association between asthma and need for fertility treatment among women with live births.All women enrolled in the Management of Asthma during Pregnancy (MAP) programme at Hvidovre Hospital, Denmark were each matched with the next three consecutive women giving birth at Hvidovre Hospital. Information from the Danish National Assisted Reproductive Technology (ART) registry was cross-linked with the Danish Medical Birth registry to identify live births. The primary outcome of interest was births following fertility treatment.Our sample comprised pregnancies from asthmatic mothers (n=932, described as "cases") and non-asthmatic mothers (n=2757, described as "controls"), with 12% (n=114) and 8% (n=212), respectively, having had fertility treatment (OR 1.67, 95% CI 1.32-2.13; p<0.001). This association remained statistically significant after adjusting for confounders, including body mass index (OR 1.31, 95% CI 1.00-1.70; p=0.047). In women ≥35 years, 25% of cases (n=63) and 13% of controls (n=82) received fertility treatment (OR 2.12, 95% CI 1.47-3.07; p<0.001), which also remained statistically significant after adjusting for confounders (OR 1.65, 95% CI 1.11-2.46; p=0.013).A higher proportion of the births from asthmatic mothers involved fertility treatment compared to non-asthmatic mothers, not least among women aged ≥35 years.