Researchers say that air pollution during pregnancy may increase the risk of lower birthweight babies, even at pollution levels below those deemed acceptable in current European Union air-quality directives. This is according to a study published in The Lancet Respiratory Medicine.

A team of European researchers used data from the European Study of Cohorts for Air Pollution Effects (ESCAPE). They analyzed 14 cohort studies from 12 European countries, involving 74,000 women who had singleton babies between 1994 and 2011.

The researchers estimated the air pollution concentrations of nitrogen oxides and particulate matter at the home addresses of the participants, using land-use regression models.

In addition, the team recorded traffic density on the nearest road and total traffic load on all major roads within 100 meters of the participants’ homes.

The findings showed that all air pollutants, particularly fine particulate matter (PM 2.5 – with a diameter of 2.5 micrometers or less), and traffic density reduced the average head circumference of a child at birth and increased the risk of low birthweight at term.

In the study population, average pollution exposure levels ranged from less that 10 micrograms per cubic meter (10µg/m³) to almost 30µg/m³.

The researchers estimate that for every increase of 5µg/m³ in exposure to PM 2.5 throughout pregnancy, the risk of low birthweight at term increases by 18%.

The researchers say:

We have shown that ambient air pollutants, particularly PM 2.5, and traffic density are associated with increases in risk of low birthweight at term and reductions in birthweight and birth head circumference.

Our findings suggest that in-utero exposure to ambient air pollution in European urban areas could explain a substantial proportion of cases of low birthweight at term.”

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Air pollution during pregnancy may increase the risk of babies having a low birthweight and small head circumference.

The study authors say that this risk persists even at levels below 25µg/m³ – the current EU annual air quality limit.

However, they note that if air pollution exposure levels were reduced to 10 µg/m³ – the current World Health Organization (WHO) annual average air quality guideline – this could prevent 22% of term low birthweight cases.

“Our findings suggest that a substantial proportion of cases of low birthweight at term could be prevented in Europe if urban air pollution, particularly PM 2.5, was reduced,” say the study authors.

Dr. Marie Pedersen of the Centre for Research in Environmental Epidemiology in Barcelona, Spain, says these findings should prompt policy makers to review air quality:

The widespread exposure of pregnant women worldwide to urban ambient air pollution at similar or even higher concentrations than those assessed in our study provides a clear message to policy makers to improve the quality of the air we all share.”

Dr. Pedersen told Medical News Today that as well as policy makers initiating changes to reduce air pollution, pregnant women can make small changes to reduce exposure themselves. These include:

  • Avoiding frequent and long-duration of commute and physical activities in rush hours, heavy traffic and other polluted areas.
  • Choosing a location of the home during pregnancy in rural areas or areas with less dense traffic, household and industry instead of urban areas, or a home facing green back yard or located at high-level floor instead of ground-level.
  • Increasing cleaner heating of homes (promote geothermic heating, energy efficient housing insolation and reduce emissions from, for example, wood burning).
  • Frequent cleaning of the home and living environment (vacuum cleaning with HEPA-filters, frequent ventilation of indoor air, location of bedroom away from rooms facing heavy traffic).
  • Minimizing indoor sources of air pollution (gas and wood heating and cooking, smoking) and ventilating the home well.

“Note that not all women are in a situation in which they can reduce their exposure to urban air pollution,” Dr. Pedersen told Medical News Today. “Unlike risk factors such as diet and smoking, air pollution is an exposure that is more complicated to reduce through individual actions.”

Earlier this year, Medical News Today reported that pregnant women exposed to high levels of air pollution are twice as likely to have a child with autism.