Almost a third of women on asthma 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 study from the Netherlands.
A lack of oxygen during development, known as hypoxemia, is one of the dangers to a foetus when its mother has uncontrolled asthma.
Researchers, whose findings appeared in the Journal of Allergy and Clinical Immunology, 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 per cent, received a prescription for an asthma medication at least once during the study period, from 1994 to 2009.
Both the Global Initiative for Asthma (GINA) and the US National Asthma Education and Prevention Programme recommend that women continue taking asthma medications throughout pregnancy, because the risks of exacerbated asthma are greater than the risks of the medications.
Between 1994 and 2003, the women’s rate of asthma control medication prescriptions held steady before, during and after pregnancy, said the researchers, led by Priscilla Zetstra-van der Woude at the University of Groningen.
From 2004 to 2009, however, the researchers saw a drop of 30 per cent in the rate of asthma prescriptions filled in the first three months of pregnancy, compared to the months before becoming pregnant.
“Many women stop or reduce their use of asthma medications when they become pregnant. Strategies to safely control asthma during pregnancy are needed,” the researchers wrote.
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 per cent during the first trimester, from roughly 1.2 per cent of pregnancies in the database down to 0.6 per cent.
“Long-acting bronchodilators are usually prescribed for patients with more severe asthma, and discontinuation could lead to severe symptoms of respiratory distress,” they wrote.
The 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 researchers could also not determine why mothers-to-be stop taking their 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 foetus,” she said. “You can have babies that will be small for their gestational age or birth weight.”
But researchers also noted that the course of asthma often changes during pregnancy, with some women having relief from symptoms and thus needing less or no medication - which is not a problem as long as the asthma is controlled.