Association between preconception and early pregnancy exposure to fine particulate matter and nervous system anomalies: a nested case-control study.

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Although several environmental factors may increase the risk of nervous system anomalies, the association between exposure to particulate matter with an aerodynamic diameter of ≤ 2.5μm (PM2.5) and nervous system anomalies is not completely understood. This study aimed to examine the association between expoure to PM2.5 and nervous system anomalies, including specific phenotypes during preconception and early pregnancy and determine the crucial time windows. We conducted a nested case-control study from the Taiwan Maternal and Child Health Database between 2004 and 2017. We applied satellite-based models with a 1km resolution to estimate the weekly average PM2.5 from 13 weeks before conception to the first 8 weeks of pregnancy. We used conditional logistic regression with distributed lag nonlinear models (DLNMs) to assess the effects of weekly average PM2.5 on the risk of nervous system anomalies and exposure-response relationships. We identified 12,383 incident nervous system anomalies cases in 2,571,300 participants. A 10µg/m³ increase in PM2.5 concentrations from a reference value of 25µg/m³ was associated with higher risk of nervous system anomalies (adjusted odds ratio [aOR]: 1.21; 95% confidence incidence [CI]: 1.18, 1.25) and encephalocele (aOR: 1.56; 95% CI: 1.33, 1.84) from 13 weeks before conception to the first 8 weeks of gestation. Anencephaly showed a significant association with PM2.5 exposure during the 13 weeks before conception (aOR: 1.48; 95% CI: 1.02, 2.51). In DLNMs, the risk of nervous system anomalies was elevated each week from 8 to 11 weeks before conception to 1-8 weeks of gestation. Our findings suggest that exposure to PM2.5 during preconception and early pregnancy may increase the risk of nervous system anomalies in offspring, particularly neural tube defects such as anencephaly and encephalocele.