By Reuters Staff

(Reuters Health) – Asthma attacks during pregnancy are associated with an increased risk of complications for mothers and their babies, a Canadian study suggests.

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.

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.

“However, our study indicates that severe asthma symptoms present the greater risk to mother and baby,” To said.

While the study wasn’t designed to prove whether or how asthma attacks during pregnancy might cause complications for mothers or babies, it’s possible this happens because flare-ups reduce oxygen supplies for both women and their developing infants, To said.

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.

About one in three pregnant women with asthma have exacerbations during pregnancy, previous research has found. These exacerbations have been previously linked to complications like high blood pressure for mothers and early arrivals for babies, but much of the research to date has compared women with and without asthma, making it unclear how much uncontrolled asthma might play a role, the study team notes.

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

Asthma attacks during pregnancy were rare, even though all of the study participants had asthma. A total of 2,663 women had asthma attacks during a total of 4,455 pregnancies, the study found.

Pregnant women who had asthma attacks were more likely to be older, and more likely to smoke or to have limited income or insecure housing, the study found.

Preeclampsia developed in 5.3% of pregnancies among women who did have asthma attacks, and just 3.8% of pregnancies among other women in the study.

In addition, women developed pregnancy-induced hypertension in 7% of pregnancies involving asthma attacks, compared with 5.4% of other pregnancies.

Low birth weights occurred in 6.8% of pregnancies with asthma attacks, compared with 5.3% of other pregnancies, the study also found. Similarly, preterm births occurred in 8.2% of pregnancies involving asthma attacks compared with 6.7% of other pregnancies.

When women had asthma attacks during pregnancy, their children were also more likely to experience allergies and respiratory infections like pneumonia.

And, 6.2% of babies had birth defects in pregnancies involving asthma attacks, compared with 5% of infants born to mothers who didn’t have asthma attacks during pregnancy.

Children were also 23% more likely to develop asthma in early childhood when mothers had asthma attacks during pregnancy. These children were also 12% more likely to have pneumonia during their first five years of life.

Women were considered to have asthma attacks or severe asthma exacerbations if they visited a doctor at least five times for asthma problems during pregnancy or if they went to a hospital or emergency room for asthma symptoms.

One limitation of the study is that this definition might not always correctly identify women with uncontrolled symptoms, the study authors note. Some women with five or more checkups for asthma symptoms during pregnancy could in fact be controlling their illness well.

Even so, the results underscore the importance of careful asthma management during pregnancy, Professor Jorgen Vestbo, chair of the European Respiratory Society’s Advocacy Council and a researcher at the University of Manchester in the UK, said in a statement.

SOURCE: European Respiratory Journal, online November 26, 2019.