High levels of air-pollution linked to miscarriage

Researchers are calling for air pollution levels to be cut in order to protect the health of the next generation.

Tommy’s news, 15/01/2019

Air pollution could be as bad for pregnant women as smoking, raising their risk of miscarriage, according to a new study from the US. 

Previous studies have analysed the effects of long term exposure to pollution on fetuses, connecting the exposure to an increased risk of premature birth and low birth weight, but shown inconclusive links to miscarriage.

This current study is the first to explore the impact of short term exposure to air pollution on pregnant women. From a sample of more than 1,300 women in Salt Lake City, it found that short term, exposure to raised levels of nitrogen dioxide (NO2) pollution increased the risk of losing a pregnancy by 16%. Nitrogen dioxide levels in Salt Lake City, where the research was carried out, are similar to those in worldwide cities such as London and Paris.

Dr Matthew Fuller, who led the research at the University of Utah, said: 

If you compare that increase in risk to other studies on environmental effects on the fetus, it’s akin to tobacco smoke in first trimester pregnancy loss.

The way that air pollution could harm a fetus has not yet been established but a likely theory is that the pollutants cause stress and inflammation.

Tommy's researcher, Professor Andrew Shennan of the Tommy’s Preterm Surveillance Clinic comments on the current research:

If the effects of air pollution on miscarriage shown in this particular research study are real, this is an important factor which could affect millions of pregnancies around the world. However, there are many other causes of miscarriage, such as genetic abnormalities at time of conception, which are more common. In order to produce clear findings, this study should have evaluated these other factors alongside air pollution, and crucially also compared this with gestational age.

Dr Fuller told The Guardian he started his research after a family member miscarried during a poor period of air quality in 2016. His study analysed the records of more than 1,300 women who attended the emergency department in Salt Lake City after miscarriages from 2007 and 2015.

It compared participants’ exposure to air pollution at the time of miscarriage to exposure at other times, accounting for age, weight and other personal factors. The strongest link found with a lost pregnancy was the level of NO2 in the seven days before the miscarriage.

Pregnant women are recommended to avoid exertion on polluted days and consider purchasing indoor air filters. 

Miscarriage research

Up to 1 in 4 women will experience a miscarriage in their lifetime. Many miscarriages are unreported and some go unnoticed as it happens so soon. Among women who know they are pregnant, it is estimated that 1 in 6 pregnancies end in miscarriage. Tommy’s conducts research to find out what puts women at risk of miscarriage in order to prevent it.

Read more about Tommy’s current miscarriage research

Miscarriage research highlights

  • The SIMPLANT trial is researching a drug that could increase stem cells in the wombs of women who have suffered recurrent miscarriage.
  • We are testing fetal DNA to see if miscarriages happened for genetic reasons. This could help parents suffering miscarriage to find explanations for their loss.
  • We are following up on studies that appear to show that damage to the DNA of sperm can more than double the risk of miscarriage.
  • The CONCEIVE trial is looking to see if differences in women’s heart and blood vessels before or early in pregnancy can lead to miscarriage.
  • The EPOS study is looking at over 1,100 women from 5 weeks of pregnancy through to delivery to help us understand why some women are more at risk of miscarriage than others.
  • We are in the process of building Tommy’s Net, a platform that will help us to collect and store information from many different hospitals. By sharing information, we will be able carry out more effective research.
  • Tommy’s has helped secure a £1.8 million National Institute of Health Research grant for the MifeMiso trial, which looks at the best way to medically treat miscarriage.