Previous studies in this area have suggested that pregnant women with asthma and who are taking asthma medication are at increased risk of a number of adverse negative effects compared with women who do not have asthma, for example premature labour, birth defects, and high maternal blood pressure.
A test conducted Between April 1997 and June 2000 including 2,205 women concluded that asthmatic women were no more likely than non-asthmatics to have a premature birth, regardless of how severe their symptoms were.
Initially, four medications (leukotriene antagonists, chromones, theophylline and steroid tablets) seemed to increase the risk of having a premature birth, but when this was studied in detail, only steroid tablets and theophylline was shown to definitely cause this increased risk.
Stunted growth in the womb was linked to the severity of the asthma symptoms, especially in women who experienced asthma symptoms during the study, but had not been diagnosed with asthma prior to it. None of the medications studied were shown to stunt growth in the womb.
Researchers concluded that asthma in itself does not increase the risk of having a premature birth, but taking steroid tablets or theophylline does. No increased risk was seen with taking inhaled corticosteroids.
The risk of low birth weight or size increases with the severity of the asthma symptoms, regardless of the medication. The authors recommend a more active treatment of pregnant women with mild or moderate asthma, but to add steroid tablets only if the asthma gets considerably worse.