Researchers examined data on more than 103,000 pregnancies among more than 58,000 women with asthma who had babies in Ontario, Canada, from 2003 to 2012.

Axar.az reports citing Reuters that compared to women who didn’t have asthma attacks during pregnancy, those who did were 17% more likely to have pregnancy-induced hypertension and 30% more likely to have dangerously high blood pressure known as preeclampsia, the study found.

Women who had asthma attacks were also 14% more likely to have low-birthweight or preterm babies and 21% more likely to have infants with birth defects.

“Nearly 40% of pregnant women decrease or stop taking asthma medication because they are worried that it could be harmful to their unborn babies,” senior study author Teresa To of the Hospital for Sick Children in Toronto and the Children’s Hospital of Eastern Ontario Research Institute in Ottawa said in a statement.

Asthma is the most common chronic disease encountered in pregnancy, occurring in up to 13% of pregnancies, To and colleagues write in the European Respiratory Journal.

For the current study, researchers followed women through pregnancy then followed their babies for up to five years.