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 foetus 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 Dr 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 foetus. You can have babies that will be small for their gestational age or low birth weight," Dr Blais said.
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. Hypoxemia is one of the dangers to a foetus when its mother has uncontrolled asthma.
Sticking to prescription
According to the GINA guidelines, there is not much evidence showing that asthma medications are harmful to the foetus, 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%) 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% 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.
Pregnancy, an extra hurdle
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 were less popular during pregnancy than shortly before.
Prescriptions for these drugs declined by about 50% during the first trimester, from roughly 1.2% of pregnancies in the database down to 0.6%.
The researchers published 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.
"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.
Dr 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 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 foetus’s health," she said.
How is asthma diagnosed?
How is asthma treated?
Causes of asthma