Air pollution and pre-eclampsia; associations and potential mechanisms

Air pollution has significant negative health impacts, particularly on the cardiovascular system. The aims of this narrative review were to identify whether there is an association between air pollution and the incidence of pre-eclampsia, and the potential mechanisms by which any effects may be mediated. We undertook a literature search using Google Scholar, PubMed, the Cochrane Library and NICE Evidence. The primary eligibility criterion was articles correlating exposure to air pollution with incidence of pre-eclampsia. Meta-analyses currently show a positive association between pre-eclampsia and exposure to both particulate matter PM2.5 and nitrogen dioxide, but no significant associations with ambient ozone or carbon monoxide exposure. No meta-analysis has been performed for exposure to sulfur dioxide. Variability in terms of quantification of exposure, the exposure period and co-founders among the studies makes comparisons complex. Adverse effects on trophoblast invasion and placental vascularisation, and increases in oxidative stress and anti-angiogenic factors, such as sFlt-1, in response to air pollution provide pathways by which exposure may contribute to the pathophysiology of pre-eclampsia. So far, studies have not discriminated between the early- and late-onset forms of the syndrome. Future prospective studies using personal air pollution monitors and blood biomarkers of pre-eclampsia would strengthen the associations. Interactions between pollutants are poorly documented, and at present there is minimal informed advice available to women on the need to avoid exposure to air pollutants during pregnancy. •Meta-analysis shows a positive association between pre-eclampsia and PM2.5 exposure.•Meta-analysis shows a positive association between pre-eclampsia and NO2 exposure.•No significant association exists between pre-eclampsia and ambient CO exposure.•NO2 and PM2.5 exposure alter placental characteristics in vivo and in vitro.•NO2 and PM2.5 cause maternal endothelial cell stress, a concern in pre-eclampsia.