Individual ambient ozone exposure during pregnancy and adverse birth outcomes: Exploration of the potentially vulnerable windows

Abstract

Background: Ambient ozone (O₃) exposure during pregnancy might be associated with preterm birth (PTB) and low birth weight (LBW); however, existing evidence remains inconclusive. It is necessary to explore the relationships and potential susceptible periods further.

Methods: To explore the relationship between O₃ exposure and adverse birth outcomes, a study using records of 34,122 singleton live births in Beijing between 2016 and 2019 was conducted. The O₃ exposure in each gestational week of pregnant women was estimated, and Cox proportional hazard models were used to estimate the hazard ratios (HRs) and corresponding 95% confidence intervals (CIs). Distributed lag nonlinear model (DLNM) incorporated in Cox proportional hazard models were used to explore potential critical windows.

Results: An increase of 10 μg/m³ in O₃ exposure was associated with a 3.9% (95%CI: 0.6-7.3%) higher risk of PTB. Additionally, this increase in O₃ exposure was positively linked to PTB during the 2nd - 7th, 22nd - 29th, and 37th gestational weeks, and LBW during the 2nd - 7th, 24th - 29th, and 37th gestational weeks.

Conclusions: This study demonstrates a positive correlation between O₃ exposure and PTB, and identified specific sensitive periods during pregnancy when the risk was higher.

Keywords: Critical sensitive window; Low birth weight; O(3) exposure; Preterm birth.