Air pollution and fecundability: Results from a Danish preconception cohort study

Background Animal and epidemiologic studies indicate that air pollution may adversely affect fertility. Epidemiologic studies have been restricted largely to couples undergoing fertility treatment or have retrospectively ascertained time‐to‐pregnancy among pregnant women. Objectives We examined the association between residential ambient air pollution and fecundability, the per‐cycle probability of conception, in a large preconception cohort of Danish pregnancy planners. Methods During 2007–2018, we used the Internet to recruit and follow women who were trying to conceive without the use of fertility treatment. Participants completed an online baseline questionnaire eliciting socio‐demographic characteristics, lifestyle factors, and medical and reproductive histories and follow‐up questionnaires every 8 weeks to ascertain pregnancy status. We determined concentrations of ambient nitrogen oxides (NOx), nitrogen dioxide (NO2), carbon monoxide (CO), ozone (O3), particulate matter