# Ozone Exposure and Gestational Diabetes in Twin Pregnancies: Exploring Critical Windows and Synergistic Risks

## TL;DR

This study finds that ozone exposure before and during twin pregnancies increases the risk of gestational diabetes, especially when combined with other risk factors.

## Contribution

The study identifies critical windows and synergistic effects of ozone exposure with maternal factors in twin pregnancies related to gestational diabetes.

## Key findings

- A 10 μg/m³ increase in ozone exposure before pregnancy was linked to a 26% higher GDM risk.
- Critical windows for ozone exposure were found preconception and during weeks 17-19 of gestation.
- Ozone exposure synergized with advanced maternal age and a history of preterm birth/abortion/stillbirth to increase GDM risk.

## Abstract

The relationship between ozone (O3) exposure and gestational diabetes mellitus (GDM) in twin pregnancies remains unexplored. This study aimed to investigate the association between O3 exposure and GDM risk in twin pregnancies, and to explore the synergistic effects of O3 exposure with other maternal factors. A total of 428 pregnancies recruited from a prospective twin cohort were included. Cox proportional hazard models with distributed lag non-linear models (DLNMs) were applied to examine the associations between O3 exposure and the risk of GDM and to identify the critical windows. The multiplicative and additive interaction were further analyzed to test the synergistic effects. A 10 μg/m3 increase in average O3 exposure during the 12 weeks before pregnancy was associated with a 26% higher risk of GDM. The critical windows were identified in the period from the 3rd week before gestation to the 2nd gestational week as well as from the 17th to 19th gestational week. There were synergistic effects between high O3 exposure during preconception and advanced maternal age, and a history of preterm birth/abortion/stillbirth. Periconceptional O3 exposure could increase the risk of GDM in twin pregnancy women, and the synergism of O3 exposure with certain GDM risk factors was observed.