Published In
Medrxiv : the Preprint Server for Health Sciences
Document Type
Pre-Print
Publication Date
10-23-2025
Abstract
Ambient air pollution is associated with adverse pregnancy outcomes such as stillbirth, miscarriage, and preterm birth. However, its effects on the viability, implantation, and survival of conceptuses-largely unobserved before the clinical detection of pregnancy-remain poorly understood. Shifts in the sex ratio at birth (SRB) provide a sensitive, population-level indicator of sex-biased conception and pregnancy loss. This systematic review examined whether maternal exposure to ambient air pollution before conception and during pregnancy is associated with deviations in the SRB. We searched MEDLINE, Embase, and Global Health from inception to 12 February 2025 for observational studies assessing both ambient air pollution exposure and SRB. Eleven studies met the inclusion criteria, representing data from eight countries spanning 1970-2023. PM was the most frequently investigated pollutant, followed by PM. Six studies reported no significant association, while four observed increased feminisation with higher exposure levels. Air pollution may plausibly influence SRB through effects on gamete quality, conceptus viability, and placental development. The SRB therefore provides a valuable proxy for detecting early biological vulnerability, revealing effects of air pollution that are otherwise hidden due to the selective observation of clinically recognised pregnancies. However, current evidence remains limited, heterogeneous, and inconclusive. As ambient air quality continues to deteriorate, more standardised research is needed to improve comparability and quantify the impact of air pollution on reproductive outcomes.
Rights
Copyright (c) 2025 The Authors
This work is licensed under a Creative Commons Attribution 4.0 International License.
DOI
10.1101/2025.10.21.25338487
Persistent Identifier
https://archives.pdx.edu/ds/psu/44301
Publisher
Cold Spring Harbor Laboratory
Citation Details
Gazeley, U., Eilerts-Spinelli, H., Abdel Ghany, J., Bonell, A., & Wilde, J. (2025). Ambient air pollution and the sex ratio at birth: a systematic review and narrative synthesis.
Description
Pre-print