Pregnant Women Exposed to Air Pollutant Ozone Develop Pre-Eclampsia

Exposure to high levels of air pollutant ozone (O3) during the early stages of pregnancy can lead to the onset of pre-eclampsia and can increase the risks of premature birth, a new study says.

Pre-eclampsia is a condition that triggers hypertension and will have a negative impact on both the pregnant woman and her baby. Between 5 and 8 percent of pregnancies in the United States is affected by this condition. Women suffering from pre-eclampsia will have high blood pressure, fluid retention and protein in the urine, leading to an adverse impact on the growth of the unborn baby in the uterus. The exact cause of this condition is not yet fully known.

For the study, researchers looked at 121,000 pregnant women in Sweden. Information about the mother's health, history of asthma and levels of air pollution caused by ozone were drawn from national data.

At the end of the study, researchers found the air pollutant ozone playing an important role in the development of pre-eclampsia, particularly among women with asthma. Women who had a history of asthma were found at 10 percent higher risks of pre-eclampsia and 25 percent greater risks of giving birth to a baby before completing the gestational age. Babies born before 37 weeks of gestational age are considered to be premature babies.

These alarming findings come at a time when about one in every 100 pregnant women is affected with asthma during pregnancy. Asthma is an inflammation of the air passage, leading to a narrowing of the airways that carry air from the mouth and nose to the lungs.

"Increased levels of O3 during the first trimester increased the risk of pre-eclampsia and preterm birth," the authors wrote. "Air pollutants did not exhibit any effects on fetal growth restriction. We estimated 1 in every 20 cases of pre-eclampsia to be associated with O3 exposure."

Findings of the study have been published in the journal BMJ Open.