There is ‘suggestive evidence’ for a link between air pollution and a heightened risk of stillbirth, scientists have suggested.
Research has suggested a 4 ug/m3 increase in exposure to small particulate matter of less than 2.5 in diameter (PM2.5) is associated with a 2% increased risk of stillbirth, along with exposure to nitrogen dioxide, carbon monoxide and ozone.
The study authors say they are cautious to interpret limited findings as conclusive as influential factors need to be controlled for, such as obesity, alcohol use and stress which may also influence stillbirth. They also warn air pollution rates may differ within cities as well as between them which could further influence results.
The authors conclude: ‘However, the existing evidence is suggestive of causality for air pollution and stillbirth without precise identification of the timing of exposure. With the limited studies on the relevant topic, our review suggests strong priorities for future research.
‘Stillbirth is one of the most neglected tragedies in global health today, and the existing evidence summarised by the authors deserves additional investigation. If the evidence of an association between ambient population and stillbirth is confirmed in future studies, it would be of major of major public health importance.’
Professor Kevin McConway, Emeritus Professor of Applied Statistics at The Open University, said the results should be interpreted cautiously: ‘Stillbirth is an important health problem worldwide, and there is no simple answer to the question of what causes it. Many factors contributing to stillbirth risk have been identified. Also, air pollution is known to have various adverse effects on health. So it’s natural to investigate whether there is any link between a mother’s exposure to pollutants in the air she breathes and the risk of stillbirth. Several such studies have been done in various parts of the world, and no clear pattern has emerged from their findings yet. So it made good sense for this new review to be carried out, to try to make more sense of the complexity in the individual studies.
‘Since this review doesn’t provide a smoking gun (to make a dreadful pun), it’s reasonable that it calls for more and better evidence. That evidence won’t be quick or easy to find. Whether or not there’s a link to stillbirth, it remains a good idea for governments and authorities to act on air pollution, since it has so many other health consequences. And I don’t think these new findings should be a serious cause for concern for individual pregnant women – if there is an increased risk of stillbirth, this review indicates that the increase is pretty small.’
Stillbirths occur when a baby dies after 24 weeks into pregnancy, prior to 24 weeks a death is known as a miscarriage. One in every 200 births in the UK ends in a stillbirth. The reasons for stillbirths can be complex and varied, many include placental complications, infections or pre-eclampsia.