# Susceptible window identification of the relationship between maternal ozone exposure and preterm birth

## TL;DR

This study finds that ozone exposure during mid-pregnancy may increase the risk of preterm birth, highlighting a critical window for prevention.

## Contribution

Identifies mid-pregnancy as a susceptible window for ozone exposure linked to preterm birth through a meta-analysis.

## Key findings

- Ozone exposure during pregnancy is positively associated with preterm birth (OR 1.065).
- Gestational weeks 13–27 are identified as a critical susceptible window (OR 1.033).

## Abstract

Previous studies have focused on the effects of ozone (O3) exposure and preterm birth (PTB), but the findings are contentious and the susceptible window for O3 exposure during pregnancy remains inconclusive. Here, we pooled the current evidence to explore the relationship between maternal O3 exposure and PTB and further identified the susceptible exposure windows. We pooled a meta-analysis of 17 eligible studies by searching Embase, PubMed and Web of Science through 9 September 2024. The odds ratio (OR) and the corresponding 95% confidence intervals (CIs) were extracted for analysis. The tests for heterogeneity, sensitivity and publication bias between studies were performed using Stata 15.0 (StataCorp, College Station, TX, USA). The combined results showed a positive association between O3 exposure and PTB (n=13; OR 1.065 [95% CI 1.056 to 1.073]), and middle pregnancy (gestational weeks 13–27) may be a susceptible window of O3 exposure with PTB (n=11; OR 1.033 [95% CI 1.029 to 1.036]). This meta-analysis suggested that O3 exposure during pregnancy may independently increase the risk of PTB and gestational weeks the 13–27 is a critical window for preventing this risk. Reducing outdoor activity or a wearing protective mask and multiple micronutrients supplementation during pregnancy may reduce the risk of O3 exposure in PTB.