Maternal exposure to fine particulate matter and congenital heart defects during preconception and pregnancy period: A cohort-based case-control study in the Taiwan maternal and child health database

Background: Few studies have explored the association between maternal exposure to particulate matter with an aerodynamic diameter of <= 2.5 mu m (PM2.5) and congenital heart defects occurring before and during pregnancy. We aimed to investigate the association and the critical time windows between the maternal exposure to PM2.5 and congenital heart defects. Method: We conducted a cohort-based case-control study of 507,960 participants obtained from the Taiwan Maternal and Child Health Database between 2004 and 2015. We applied satellite-based spatiotemporal models with 1-km resolution to calculate the average PM2.5 concentration during preconception and the specific periods of pregnancy. We also performed conditional logistic regression with distributed lag non-linear models (DLNMs) to assess the effects of weekly average PM2.5 on both congenital heart defects and their isolated subtypes, as well as the concentration-response relationships. Results: In DLNMs, exposure to PM2.5 (per 10 mu g/m3) during weeks 7-12 before conception and weeks 3-9 after conception was associated with congenital heart defects. The strongest association at 12 weeks before conception (odds ratio [OR] = 1.026, 95% confidence intervals [CI]: 1.012-1.040) and 7 weeks after conception (OR = 1.024, 95% CI: 1.012-1.036) for every 10 mu g/m3 increase in PM2.5 concentration. In modification analysis, strongest associations were observed for low SES. Conclusions: Our study revealed that exposure to ambient PM2.5 raises the risk of congenital heart defects, particularly among individuals with lower socioeconomic status. Moreover, our findings suggest that preconception exposure to PM2.5 may be a crucial period for the development of congenital heart defects.