Air pollution is high on the news agenda. Many UK cities are in breach of EU clean air regulations and are looking to see how the situation can be improved. Consideration is being given to ultra-low emission zones, banning cars idling and controls over wood-burning stoves, among many other initiatives.
Advice from the Department for Environment, Food and Rural Affairs (DEFRA) (2019) on air pollution refers only to children and those at risk due to lung or heart disease. It does not mention pregnant women. This is a serious oversight, given the emphasis on stopping smoking and avoiding second-hand smoke.
Does DEFRA not know the risks of air pollution for pregnant women? A study by Malley et al (2017) showed that air pollution was linked to 2.7 million preterm births worldwide. This study identified that particulate matter (from diesel vehicles, fires and industrial emissions) was a major cause. This is worrying, as UK cities have high levels of particulates in the air.
It has also been suspected that air pollution reduces birthweight independently of gestation. However, as air pollution is variable, it has been difficult for researchers to produce consistent results. Many cities in the developing world experience high levels of pollution. One such is Beijing and in the run–up to the 2008 Olympic and Paralympic Games, there were 47 days of restrictions, resulting in an 18–59% reduction in pollution, compared to pre-Olympic levels. Rich et al (2015) compared birthweights for term babies during the 2-month Olympic window with the same time period the year before and the year after. The strongest association was for those babies who experienced their 8th month of gestation during the Games, who were, on average, 23 g heavier than babies whose 8th month occurred during the same period in 2007 or 2009.
‘In the run–up to the 2008 Olympic and Paralympic Games, there were 47 days of restrictions, resulting in an 18–59% reduction in pollution, compared to pre-Olympic levels’
Another long-term effect of exposure to particulate matter during pregnancy is an increased risk of autism spectrum disorder. A longitudinal cohort study by Raz et al (2015) showed the strongest associations for higher exposure in the third trimester.
So, how do we advise women? Although it is possible to stop smoking and to avoid places where people are smoking, we can't stop women going outside and exercising—and indeed we would not wish to do so.
The National Institute for Health and Care Excellence (NICE) (2017) guideline on outdoor air pollution and health does at least, in its glossary, acknowledge effects on fetal growth and preterm birth. It does not mention pregnant women, although there is one mention in the draft standard (NICE, 2018). The draft standard identifies the initial antenatal appointment as an opportunity to advise women on how to minimise their exposure and manage related symptoms (it does not suggest how the time to do so might be found).
The question of whether midwives know what to advise remains. Pregnant women often travel to and from work, take their children to school or run errands; it is not feasible to advise women to stay at home. Midwives need clear, practical and simple advice as to what women should avoid if they can, including whether some modes of transport are better than others, whether women should ask for a variation in the working day to avoid rush hours and whether there are occasions when they should not travel.
It is hard not to assume a link between the UK's high perinatal mortality rates and the levels of air pollution. Something must be done for the next generation.