Association between maternal exposure to ambient PM and neural tube defects: A case-control study in Liaoning Province, China.

Background: The potential association between maternal exposure to ambient PM and offspring neural tube defects (NTDs) is a contentious issue. This study aims to evaluate the aforementioned association at a provincial level in China.

Methods: A total of 2736 cases and 7950 randomly selected healthy infants included in the Maternal and Child Health Certificate Registry of Liaoning Province and delivered between 2010 and 2015 were recruited. Daily PM concentrations were obtained from all available monitoring stations located within the study area. A multivariable logistic regression model was established to calculate the adjusted odds ratios (ORs) and 95% confidence intervals (CIs).

Results: PM exposure was significantly associated with the risk of NTDs during the three months preconception (per 10 μg/m increment: OR = 1.10, 95% CI 1.07-1.14; per standard deviation [27 μg/m] increment: OR = 1.29, 95% CI 1.18-1.41; highest tertile: OR = 1.61, 95% CI 1.37-1.91) and the first trimester (highest tertile: OR = 1.57, 95% CI: 1.31-1.87). When focusing on shorter exposure windows, similar associations were observed for PM exposure from the third month before pregnancy to the third month after pregnancy. Sensitivity analyses using propensity score matching yielded consistent findings.

Conclusions: Maternal exposure to PM is positively associated with NTDs during the critical period of fetal neural tube development. However, due to the limitation of the exposure assessment as well as potential residual confounding, further research is warranted to confirm our findings.