NEW YORK (Reuters Health) - Almost a third of women on asthma control medications stop using them during the first few months of pregnancy - despite advice that a mother's uncontrolled asthma is more dangerous to the developing fetus than the drugs, according to a new study from the Netherlands.
The researchers could not determine why moms-to-be stop taking their asthma meds, or whether it led to any negative health effects, but the findings are concerning, said Lucie Blais, a pharmacy professor at the University of Montreal, who was not involved in the study.
"Some studies show that uncontrolled asthma is bad for the fetus. You can have babies that will be small for their gestational age or low birth weight," Blais told Reuters Health.
Both the Global Initiative for Asthma (GINA) and the U.S. National Asthma Education and Prevention Program recommend that women continue taking asthma medications throughout pregnancy, because the risks of exacerbated asthma are greater than the risks of the medication.
A lack of oxygen during development, known as hypoxemia, is one of the dangers to a fetus when its mother has uncontrolled asthma.
According to the GINA guidelines, there is not much evidence showing that asthma medications are harmful to the fetus, and "using medications to obtain control of asthma is justified even when their safety in pregnancy has not been unequivocally proven."
To see how well pregnant mothers stick to their prescriptions, Priscilla Zetstra-van der Woude at the University of Groningen and her colleagues used information on more than 25,000 pregnancies from a prescription database in The Netherlands.
More than 2,000 of those pregnant women (about 8 percent) received a prescription for an asthma medication at least once during the study period, from 1994 to 2009.
Between 1994 and 2003, the women's rate of asthma control medication prescriptions held steady before, during and after pregnancy.
From 2004 to 2009, however, the researchers saw a drop of 30 percent in the rate of asthma prescriptions filled in the first three months of pregnancy, compared to a woman's pattern in the months before becoming pregnant.
When Zetstra-van der Woude's group looked at the types of medications that women were cutting out, they saw that long-acting bronchodilators and combinations of these drugs with inhaled corticosteroids - used to keep moderate to severe asthma under control - were less popular during pregnancy than shortly before.
Prescriptions for these drugs declined by about 50 percent during the first trimester, from roughly 1.2 percent of pregnancies in the database down to 0.6 percent.
"Long-acting bronchodilators are usually prescribed for patients with more severe asthma, and discontinuation could lead to severe symptoms of respiratory distress," the authors wrote in their report in the Journal of Allergy and Clinical Immunology.
Zetstra-van der Woude's study could not say whether the drop off in asthma medications had any negative effects on the mother or baby, and it's possible that women did not have any worsening of symptoms.
"The course of asthma often changes during pregnancy and some women may experience a relief of asthma symptoms, and as a consequence can do with less or with no medication at all. This is no problem as long as the asthma is under control," Zetstra-van der Woude said in an email to Reuters Health.
"Doctors as well as women themselves should be informed about the importance of adequate asthma control during pregnancy and about the risks of poorly controlled asthma...for the unborn child," said Zetstra-van der Woude.
Blais said asthma patients are not especially good at sticking to their medications to begin with, and pregnancy could add an extra hurdle because women might be afraid of taking any drugs during pregnancy.
On the other hand, pregnancy could serve as an opportunity to get women to become more adherent to their prescriptions if it means keeping their asthma in check.
"Maybe pregnancy could be a period in a woman's life where she might listen more to the recommendations because it's about her health, but also the fetus's health," she said.
SOURCE: tinyurl.com/9uuelcy The Journal of Allergy and Clinical Immunology, online October 15, 2012.