Urban environment in pregnancy and postpartum depression: An individual participant data meta-analysis of 12 European birth cohorts.

Background: Urban environmental exposures associate with adult depression, but it is unclear whether they are associated to postpartum depression (PPD).

Objectives: We investigated associations between urban environment exposures during pregnancy and PPD.

Methods: We included women with singleton deliveries to liveborn children from 12 European birth cohorts (N with minimum one exposure = 30,772, analysis N range 17,686-30,716 depending on exposure; representing 26-46 % of the 66,825 eligible women). We estimated maternal exposure during pregnancy to ambient air pollution with nitrogen dioxide (NO) and particulate matter (PM and PM), road traffic noise (L), natural spaces (Normalised Difference Vegetation Index; NDVI, proximity to major green or blue spaces) and built environment (population density, facility richness and walkability). Maternal PPD was assessed 3-18 months after birth using self-completed questionnaires. We used adjusted logistic regression models to estimate cohort-specific associations between each exposure and PPD and combined results via meta-analysis using DataSHIELD.

Results: Of the 30,772 women included, 3,078 (10 %) reported having PPD. Exposure to PM was associated with slightly increased odds of PPD (adjusted odd ratios (OR) of 1.08 [95 % Confidence Intervals (CI): 0.99, 1.17] per inter quartile range increment of PM) whilst associations for exposure to NO and PM were close to null. Exposure to high levels of road traffic noise (≥65 dB vs. < 65 dB) was associated with an OR of 1.12 [CI: 0.95, 1.32]. Associations between green spaces and PPD were close to null; whilst proximity to major blue spaces was associated with increased risk of PPD (OR 1.12, 95 %CI: 1.00, 1.26). All associations between built environment and PPD were close to null. Multiple exposure models showed similar results.

Discussion: The study findings suggest that exposure to PM road traffic noise and blue spaces in pregnancy may increase PPD risk, however future studies should explore this causally.