Residential proximity to major roads and fecundability in a preconception cohort

Emerging evidence from animal and human studies indicates that exposure to traffic-related air pollution may adversely affect fertility.

Among 7,342 female pregnancy planners from the United States and 1,448 from Canada, we examined the association between residential proximity to major roads and fecundability, the per-cycle probability of conception. From 2013 to 2019, women 21-45 years old who were trying to conceive without fertility treatment completed an online baseline questionnaire and follow-up questionnaires every 8 weeks for up to 12 months or until pregnancy. We geocoded residential addresses reported at baseline and during follow-up, and calculated distance to nearest major roads and length of major roads within buffers of 50, 100, 300, and 400 meters around the residence as proxies for traffic-related air pollution. We used proportional probabilities regression models to estimate fecundability ratios (FRs) and 95% confidence intervals (CIs), adjusting for individual- and neighborhood-level characteristics.

In the United States, the FR comparing women who lived <50 meters with those who lived ≥400 meters from the closest major road was 0.88 (95% CI = 0.80, 0.98). The association among Canadian women was similar in magnitude, but less precise (FR = 0.93; 95% CI = 0.74, 1.16). Likewise, length of major roads within buffers of 50 and 100 meters was associated with lower fecundability in both countries; associations were attenuated within larger buffers.

These results are consistent with the hypothesis that traffic-related air pollution or other near-road exposures may adversely affect fecundability.