Ambient air pollution and stillbirth: An updated systematic review and meta-analysis of epidemiological studies

Huanhuan Zhang; Xiaoan Zhang; Qiong Wang; Yuanzhi Xu; Yang Feng; Zengli Yu; Cunrui Huang

doi:10.1016/j.envpol.2021.116752

Ambient air pollution and stillbirth: An updated systematic review and meta-analysis of epidemiological studies

Environ Pollut. 2021 Jun 1:278:116752. doi: 10.1016/j.envpol.2021.116752. Epub 2021 Feb 22.

Authors

Huanhuan Zhang¹, Xiaoan Zhang², Qiong Wang³, Yuanzhi Xu⁴, Yang Feng⁵, Zengli Yu⁶, Cunrui Huang⁷

Affiliations

¹ School of Public Health, Zhengzhou University, Zhengzhou, China; Shanghai Typhoon Institute, China Meteorological Administration, Shanghai, China; Shanghai Key Laboratory of Meteorology and Health, Shanghai Meteorological Service, Shanghai, China.
² The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China.
³ School of Public Health, Sun Yat-sen University, Guangzhou, China.
⁴ Department of Clinical Medicine, Medical School of Zhengzhou University, Zhengzhou, China.
⁵ School of Public Health, Zhengzhou University, Zhengzhou, China.
⁶ School of Public Health, Zhengzhou University, Zhengzhou, China. Electronic address: zly@zzu.edu.cn.
⁷ School of Public Health, Zhengzhou University, Zhengzhou, China; Shanghai Typhoon Institute, China Meteorological Administration, Shanghai, China; Shanghai Key Laboratory of Meteorology and Health, Shanghai Meteorological Service, Shanghai, China; School of Public Health, Sun Yat-sen University, Guangzhou, China.

PMID: 33689950
DOI: 10.1016/j.envpol.2021.116752

Abstract

Stillbirth has a great impact on contemporary and future generations. Increasing evidence show that ambient air pollution exposure is associated with stillbirth. However, previous studies showed inconsistent findings. To clarify the effect of maternal air pollution exposure on stillbirth, we searched for studies examining the associations between air pollutants, including particulate matter (diameter ≤ 2.5 μm [PM_2.5] and ≤10 μm [PM₁₀]) and gaseous pollutants (sulfur dioxide [SO₂], nitrogen dioxide [NO₂], carbon monoxide [CO] and ozone [O₃]), and stillbirth published in PubMed, Web of Science, Embase and Cochrane Library until December 11, 2020. The pooled effect estimates and 95% confidence intervals (CI) were calculated, and the heterogeneity was evaluated using Cochran's Q test and I² statistic. Publication bias was assessed using funnel plots and Egger's tests. Of 7546 records, 15 eligible studies were included in this review. Results of long-term exposure showed that maternal third trimester PM_2.5 and CO exposure (per 10 μg/m³ increment) increased the odds of stillbirth, with estimated odds ratios (ORs) of 1.094 (95% CI: 1.008-1.180) and 1.0009 (95% CI: 1.0001-1.0017), respectively. Entire pregnancy exposure to PM_2.5 was also associated with stillbirth (OR: 1.103, 95% CI: 1.074-1.131). A 10 μg/m³ increment in O₃ in the first trimester was associated with stillbirth, and the estimated OR was 1.028 (95% CI: 1.001-1.055). Short-term exposure (on lag day 4) to O₃ was also associated with stillbirth (OR: 1.002, 95% CI: 1.001-1.004). PM₁₀, SO₂ and NO₂ exposure had no significant effects on the incidence of stillbirth. Additional well-designed cohort studies and investigations regarding potential biological mechanisms are warranted to elaborate the suggestive association that may help improve intergenerational inequality.

Keywords: Air pollution; Epidemiological study; Meta-analysis; Stillbirth; Systematic review.

Publication types

Meta-Analysis
Review
Systematic Review

MeSH terms

Air Pollutants* / analysis
Air Pollution* / analysis
Environmental Exposure / analysis
Epidemiologic Studies
Female
Humans
Nitrogen Dioxide / analysis
Ozone* / analysis
Particulate Matter / analysis
Pregnancy
Stillbirth / epidemiology
Sulfur Dioxide / analysis

Substances

Air Pollutants
Particulate Matter
Sulfur Dioxide
Ozone
Nitrogen Dioxide