Air pollution exposure ‘increases’ risk of stillbirth

Study published in the Occupational & Environmental Medicine journal establishes link between air pollution and stillbirth

Exposure to air pollution leads to a heightened risk of stillbirth among expectant mothers, scientists have claimed.

Research published in the journal Occupational & Environmental Medicine yesterday (24 May) suggested that a 4 μg/m³ increase in exposure to particulate matter — PM 2.5 — during pregnancy can be associated with an increased risk of stillbirth.

The study links air pollution exposure at pregnancy to stillbirth

The conclusions were drawn after researchers from the Centre for Environmental and Respiratory Health at the University of Oulu in Finland looked at evidence from 13 epidemiological studies that asked whether maternal exposure to ambient air pollution triggers stillbirth.

Researchers also concluded that exposure to other routinely monitored air pollutants such as nitrogen dioxide (NO₂), carbon monoxide (CO), sulfur dioxide (SO₂), PM₁₀ and ozone (O₃), could also associated with elevated risks, but not all associations reached ‘statistical significance’.

The study claimed that it is: “biologically plausible that exposure to air pollutants triggers stillbirth as residential exposure to urban air pollution during pregnancy has been linked with elevated risk of several factors associated with elevated risk of stillbirth, including maternal gestational hypertension, preeclampsia and eclampsia, gestational diabetes mellitus, term low birth weight (2500 g) and other indicators of fetal growth restriction, preterm delivery (<37 weeks of gestation) and congenital abnormalities.”

Further research

However, the authors of the report claimed that further studies needed to be carried out to strengthen the evidence of a link between air pollution exposure and still birth.

They added that a limitation of existing evidence exists due to ‘crude’ exposure assessment methods used, which in most studies relied on centralised routine air monitoring data.

In a commentary on the research on the Occupational & Environmental Medicine website, Dr Marie Pedersen of the Department of Public Health, Centre for Epidemiology and Screening, University of Copenhagen, also called for further investigation into the links between air pollution exposure and stillbirth.

She wrote: “Stillbirth is one of the most neglected tragedies in global health today, and the existing evidence, summarised by Siddika et al, deserves additional investigation.

“If the evidence of an association between ambient air pollution and stillbirth is confirmed in future studies, it would be of major public health importance. Although the reported summary effect estimates were relatively small, the ubiquitous nature of ambient air pollution exposure suggests that exposure to ambient air pollution may have a large population-attributable risk for stillbirth.

“Further studies with better measures of air pollution, potential confounders and effect modifiers, are highly recommended to confirm or refute that exposure to ambient air pollution triggers stillbirth.”