Association Between Ambient Fine Particulate Matter and Maternal Vitamin D Levels During The Second Trimester of Pregnancy

Background: Evidence for an association between the amount of ambient fine particulate matter (PM) in the atmosphere and vitamin D status of pregnant women is limited. We aimed to examine the independent association between ambient fine PM and maternal levels of serum 25-hydroxyvitamin D (25OHD) during the second trimester and to explore possible modifications to the association by meteorological factors. Methods: : 27,768 pregnant women presenting for prenatal examination who were tested for serum 25OHD concentration during the second trimester between January 1, 2016, and 31 December, 2020, were included in this retrospective analysis. Exposure to PM was evaluated based on daily average PM with an aerodynamic diameter of ≤2.5 μm (PM 2.5 ) and PM with an aerodynamic diameter of ≤10 μm (PM 10 ). Corresponding meteorological data for daily average atmospheric temperature, atmospheric pressure, relative humidity, sunshine duration, and wind speed, were collected. Results: : Vitamin D deficiency (<12 ng/mL), inadequacy (12-20 ng/mL), and adequacy (≥20 ng/mL) were respectively present in 23.5%, 41.3%, and 35.2% of pregnant women during their second trimester. The maximum cumulative effects of PM 2.5 occurred at lag 45 days, and the maximum cumulative effects of PM 10 occurred at lag 60 days. In crude models, 45-day moving daily average PM 2.5 concentrations were negatively associated with 25OHD levels (β, −0.200; 95% CI, −0.206 to −0.193), as were 60-day moving daily average PM 10 concentrations (β, −0.142; 95% CI, −0.146 to −0.137). After adjusting for temporal and meteorological factors, the effect values were drastically reduced (adjusted β of PM 2.5 , −0.032; 95% CI, −0.046 to −0.018; adjusted β of PM 10 , −0.039; 95% CI, −0.049 to −0.028). Conclusions: : Our study showed an independent negative association between ambient fine PM in the atmosphere and maternal serum 25OHD levels during the second trimester of pregnancy. However, the effect values were small after adjusting for temporal and/or meteorological factors, which indicates that ambient fine PM may have a limited influence on maternal serum 25OHD levels.