Associations of ambient air pollution exposure to fine particulate matter and its chemical constituents before and during pregnancy with the risk of full-term small for gestational age: a retrospective cohort study.

OBJECTIVE

In the current study, we explored the associations between exposure to fine particulate matter (PM2.5) constituents and full-term small for gestational age (SGA) in different periods.

METHODS

We included 155,897 participants, and matched the exposure concentrations of PM2.5 and its constituents [sulfate (SO42-), nitrate (NO3-), ammonium (NH4+), organic matter (OM), and black carbon (BC)] according to participants' geographical location. To explore the associations of prenatal exposure to PM2.5 and its constituents with the risk of full-term SGA, we used logistic regression, restricted cubic spline regression (RCS) and quartile g-computation (QGCOMP).

RESULTS

We found that individual exposure to PM2.5 and its constituents was positively associated with the risk of full-term SGA (P < 0.05), whether in the year before pregnancy or the entire pregnancy. These associations were more pronounced in the second trimester. We found that the risk of full-term SGA was positively and linearly related to the concentrations of PM2.5 and its constituents (Poverall < 0.05, Pnonlinear > 0.05). The associations of PM2.5 and its constituents with full-term SGA were stronger in multiparous mothers. Moreover, full-term SGA was associated with exposure to mixtures of SO42-, NO3-, NH4+, OM, and BC before pregnancy and in the second and third trimester. Among these, BC was positively associated with full-term SGA at each of the aforementioned stages.

CONCLUSIONS

The risk of full-term SGA was positively and linearly related to concentrations of PM2.5 and its constituents, and these associations were more pronounced in the second trimester. BC was the most hazardous constituent of PM2.5 that was associated with full-term SGA.