One in 20 cases of pre-eclampsia may be linked to levels of ozone in the air during the first three months of pregnancy, a study from Umea University in Sweden suggests.
The research, published in the online journal BMJ Open, found that mothers with asthma may be more likely to suffer from the condition, characterised by high blood pressure and the presence of protein in the urine during pregnancy.
The authors of the report say there is mounting evidence of a link between air pollution and premature birth.
The study examined almost 121,000 singleton births in Stockholm, Sweden, between 1998 and 2006, as well as national data on the prevalence of asthma among mothers and levels of air pollutants, such as ozone and nitrogen oxide from vehicle exhausts in the area.
Some 4.4% of the pregnancies resulted in a premature birth, with the prevalence of pre-eclampsia 2.7%.
There was no link between exposure to levels of vehicle exhaust and complications of pregnancy, nor were any associations found for air pollutants and babies that were underweight at birth.
After looking at the mothers’ ages, previous births, educational attainment, ethnicity, asthma, season and year of conception, the authors calculated that one in every 20 (5%) cases of pre-eclampsia was linked to ozone levels during early pregnancy.