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

Abstract

Although several environmental factors may increase the risk of nervous system anomalies, the association between exposure to particulate matter with an aerodynamic diameter of ≤ 2.5 μm (PM_2.5) and nervous system anomalies is not completely understood. This study aimed to examine the association between expoure to PM_2.5 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 1 km resolution to estimate the weekly average PM_2.5 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 PM_2.5 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 10 µg/m³ increase in PM_2.5 concentrations from a reference value of 25 µg/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 PM_2.5 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 PM_2.5 during preconception and early pregnancy may increase the risk of nervous system anomalies in offspring, particularly neural tube defects such as anencephaly and encephalocele.