Traffic-related metrics and adverse birth outcomes: A systematic review and meta-analysis

Lijun Wang, Pengyi Guo, Hui Tong, Anxu Wang, Ying Chang, Xuemei Guo, Junming Gong, Congbo Song, Lin Wu, Ting Wang, Philip K. Hopke, Xi Chen, Nai jun Tang, Hongjun Mao

Research output: Contribution to journalReview articlepeer-review


Given the inconsistency of epidemiologic evidence for associations between maternal exposures to traffic-related metrics and adverse birth outcomes, this manuscript aims to provide clarity on this topic. Pooled meta-estimates were calculated using random-effects analyses. Subgroup analyses were conducted by study area, study design, and Newcastle-Ottawa quality score (NOS). Funnel plots and Egger's test were conducted to evaluate the publication bias, and Fail-safe Numbers (Fail-safe N) were measured to evaluate the robustness of models. From the initial 740 studies (last search, July 11, 2019), 26 studies were included in our analysis. The pooled odds ratio for the change in small for gestational age associated with per 500 m decrease in the distance to roads was 1.016 (95% CI: 1.004, 1.029). Subgroup analyses revealed significant positive associations between term low birth weight and traffic density in higher-quality literatures with higher NOS [1.060 (95% CI: 1.002, 1.121)], cohort studies [1.020 (95% CI: 1.006, 1.033)], and studies in North America [1.018 (95% CI: 1.005, 1.131)]. The buffer of traffic density made no difference in the effect size. Traffic density seemed to be a better indicator of traffic pollution than the distance to roads.

Original languageEnglish
Article number109752
JournalEnvironmental Research
Publication statusPublished - Sept 2020


  • Adverse birth outcomes
  • Meta-analysis
  • Preterm birth
  • Proximity to roads
  • Small for gestational age
  • Term low birth weight
  • Traffic density
  • Traffic-related metrics


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