Many people with asthma use daily inhaled corticosteroids to control the condition and prevent asthma attacks. So women often continue on the medications during pregnancy, at the lowest dose needed, according to Beuther.

“The most important thing,” he told Reuters Health, “is that their asthma is under good control.”

A serious asthma attack, Beuther said, would deprive the fetus of oxygen, which itself is a risk. In addition, preventing asthma attacks would allow pregnant women to avoid using the oral corticosteroids used to treat them.

With the oral form, the drug goes into the bloodstream, from which it could cross into the placenta. With inhaled corticosteroids, most of the drug does not reach the bloodstream, Beuther said.

There are still questions. This study does not address whether corticosteroids might be related to some other type of birth defect, Beuther pointed out.

“We don’t know that they are harmful, but we can’t say that they are completely safe either,” he said.

Beuther suggested that women who have concerns speak with their doctor - including about whether they are on the lowest dose of corticosteroid needed to control their condition.

Hviid agreed. “What is required will differ from woman to woman and should be discussed in detail with the doctor,” he said.

“In many cases,” Hviid said, “the real risks to the mother and fetus of avoiding treatment are greater than the hypothesized risks of birth defects associated with treatment.”

SOURCE: CMAJ, online April 11, 2011