JMIR Publications

ABSTRACT

Background:

Background:

Ozone (O3) exposure is found to be associated with gestational hypertension, which, in turn increases risk of term low birth weight (LBW). As such, gestational hypertension might be a mechanism by which O3 mediates restricted fetal growth, yet few epidemiological studies have examined this potential mechanism.

Objective:

Objective:

To examine whether gestational hypertension serves as mediator of the association of prenatal O3 exposure with term low birth weight.

Methods:

Methods:

This population-based cohort study included 3,394,739 pairs of mothers and their singleton live births in Shandong province from January 1, 2016 to December 31, 2022. Exposure to O3, calculated for each participant throughout the entire pregnancy according to home address and spatiotemporal models. A 4-step mediation analysis using logistic regression was conducted, followed by a counterfactual-based causal mediation analysis, to test the mediating role of gestational hypertension.

Results:

Results:

Among the 3,394,739 term births (1,615,993 girls [47.6%]), per interquartile range increase of O3 concentration (19.93 ug/m3) was positively associated with the likelihoods of term LBW and small of gestational age (SGA), with ORs of 1.053 (95% CI: 1.031-1.074) and 1.034 (95% CI: 1.023-1.044), respectively. Gestational hypertension partly mediated the association between O3 exposure and term LBW or SGA. The contribution rates of gestational hypertension were 15.18% for term LBW and 21.68% for term SGA, respectively. The mediation effects even grew stronger under the counterfactual framework.

Conclusions:

Conclusions:

Gestational hypertension was a mediator of the association between O3 exposure and risks of term LBW. Pregnant women should take proactive measures to minimize their exposure to O3 to prevent potential adverse impacts on their developing fetuses and themselves.