Associations between Residential Green Space and Fertility in a North American Preconception Cohort Study

Abstract

BACKGROUND AND AIM: A growing body of epidemiological literature shows that exposure to green space (natural vegetation) may have positive effects on human health, including reproductive outcomes. Residential green space may improve health via reduced exposure to traffic-related air pollution, reduced depressive symptoms or stress levels, and increased physical activity. We hypothesize that increased exposure to green space may promote fecundability, a sensitive marker of fertility. METHODS: In a North American preconception cohort study (Pregnancy Study Online, PRESTO), we prospectively examined associations between residential green space (measured by satellite normalized difference vegetation index [NDVI] at a 30m resolution) and fecundability (per-cycle probability of conception) (n=8,790). From 2013 through 2019, women aged 21-45 years who were trying to conceive without fertility treatment completed online questionnaires every 8 weeks for up to 12 months. We followed participants until reported pregnancy or a censoring event (loss to follow-up, end of pregnancy attempt, initiation of fertility treatment, or 12 menstrual cycles), whichever event was first. Using geocoded residential addresses, we calculated annual maximum NDVI for 50m, 100m, 250m, and 500m buffers around each residence to quantify green space. We used proportional probabilities regression models to estimate fecundability ratios (FR), adjusting for sociodemographic and lifestyle characteristics. RESULTS:Using life table methods, 67.7% of participants conceived who were in the highest NDVI group for the 250m buffer (NDVI: 0.8-1.0; n=874), compared to only 62.0% of participants with the lowest NDVI group (NDVI: 0.0-0.2; n=162). When comparing participants with the highest to lowest NDVI values in the 250m buffer, adjusted models show an FR of 1.43 (95% CI: 1.04, 1.95). Restricted cubic splines show a nonlinear trend. Results are similar for other distance buffers. CONCLUSIONS:We present the first epidemiologic evidence that residential greenness is positively associated with fecundability. Future work will examine the role of key pathways that may mediate this relationship. KEYWORDS: Green space, Reproductive Outcomes, Female, Built environment, Environmental disparities