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. 2024 May 27;24(1):1411.
doi: 10.1186/s12889-024-18913-z.

Association between risk of preterm birth and long-term and short-term exposure to ambient carbon monoxide during pregnancy in chongqing, China: a study from 2016-2020

Xin Ming #  1   2   3   4 , Yunping Yang #  1   2   3 , Yannan Li  1   2   3 , Ziyi He  1   2   3 , Xiaoqin Tian  4 , Jin Cheng  5 , Wenzheng Zhou  6   7   8
Affiliations

Association between risk of preterm birth and long-term and short-term exposure to ambient carbon monoxide during pregnancy in chongqing, China: a study from 2016-2020

Xin Ming et al. BMC Public Health. .

Abstract

Background: Preterm birth (PTB) is an important predictor of perinatal morbidity and mortality. Previous researches have reported a correlation between air pollution and an increased risk of preterm birth. However, the specific relationship between short-term and long-term exposure to carbon monoxide (CO) and preterm birth remains less explored.

Methods: A population-based study was conducted among 515,498 pregnant women in Chongqing, China, to assess short-term and long-term effects of CO on preterm and very preterm births. Generalized additive models (GAM) were applied to evaluate short-term effects, and exposure-response correlation curves were plotted after adjusting for confounding factors. Hazard ratios (HR) and 95% confidence intervals (CI) were calculated using COX proportional hazard models to estimate the long-term effect.

Results: The daily incidence of preterm and very preterm birth was 5.99% and 0.41%, respectively. A positive association between a 100 µg/m³ increase in CO and PTB was observed at lag 0-3 days and 12-21 days, with a maximum relative risk (RR) of 1.021(95%CI: 1.001-1.043). The exposure-response curves (lag 0 day) revealed a rapid increase in PTB due to CO. Regarding long-term exposure, positive associations were found between a 100 µg/m3 CO increase for each trimester(Model 2 for trimester 1: HR = 1.054, 95%CI: 1.048-1.060; Model 2 for trimester 2: HR = 1.066, 95%CI: 1.060-1.073; Model 2 for trimester 3: HR = 1.007, 95%CI: 1.001-1.013; Model 2 for entire pregnancy: HR = 1.080, 95%CI: 1.073-1.088) and higher HRs of very preterm birth. Multiplicative interactions between air pollution and CO on the risk of preterm and very preterm birth were detected (P- interaction<0.05).

Conclusions: Our findings suggest that short-term exposure to low levels of CO may have protective effects against preterm birth, while long-term exposure to low concentrations of CO may reduce the risk of both preterm and very preterm birth. Moreover, our study indicated that very preterm birth is more susceptible to the influence of long-term exposure to CO during pregnancy, with acute CO exposure exhibiting a greater impact on preterm birth. It is imperative for pregnant women to minimize exposure to ambient air pollutants.

Keywords: Air pollution; CO; Preterm birth; Very preterm birth.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1
Fig. 1
The slice’s plots of the relative risk (95% CI) value of CO with 30 day lag for preterm and very preterm birth
Fig. 2
Fig. 2
Exposure-response association curves between CO concentration (µg/m3, lag0) and risk of preterm birth and very preterm birth. The vertical scale represents the log of relative risk of daily preterm birth and very preterm birth related to a 100 µg/m3 increment of ambient CO
Fig. 3
Fig. 3
The HRs of long-term exposure to CO with the risk of preterm birth in different age groups Note Model1 was unadjusted. Model2 was adjusted for temperature, relative humidity
Fig. 4
Fig. 4
The HRs of long-term exposure to CO with the risk of very preterm birth in different age groups Note Model 1 was unadjusted. Model 2 was adjusted for temperature and relative humidity
Fig. 5
Fig. 5
Dose-response associations (smoothing by RCS function with five knots) of preterm and very preterm with ambient CO exposure during the entire pregnancy, with the mean of CO exposure serving as the reference value. Models were adjusted for temperature and relative humidity. Hazard risk was represented by a bold line, and the 95% confidence interval was represented by the shaded area
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