Poorly controlled asthma is associated with adverse health outcomes in pregnant women and their infants, but little is known about the effect recent changes in prescribing practices (such as increased use of bronchodilator and anti-inflammatory agents) have had on perinatal outcomes. Alexander and colleagues conducted a retrospective cohort study to assess perinatal outcomes in women with asthma who used asthma medications during pregnancy.

More than 800 women with asthma who delivered between 1991 and 1992 in a Canadian hospital were identified. The women were classified into three groups based on the therapy they received for their asthma: 375 women who used no asthma medication, 303 women who used a beta agonist only and 139 women who used steroids, either alone or in combination with other medications. The pregnancy outcomes of these women were compared with those of 13,709 women without asthma who delivered at the same hospital during the same period. Women with asthma, particularly those who were not taking asthma medication, were more likely to be nulliparous and unmarried than women without asthma. Women with asthma were also more likely to smoke, with the highest rates of smoking (38 percent) reported among those who did not receive asthma treatment.

A significantly increased risk of antenatal and postpartum hemorrhage was found in women with asthma. Those treated with steroids had the highest risk. Fifteen percent of mothers in this group experienced hemorrhage, compared with 8 percent of mothers without asthma, 11.6 percent of mothers with asthma who were not receiving treatment and 10 percent of mothers with asthma who were treated with beta agonists. The risk of pregnancy-induced hypertension was also higher in women with asthma who were treated with steroids (18 percent) compared with 10.5 percent of women without asthma. The infants of women with asthma who were treated with steroids were also significantly more likely to develop hyperbilirubinemia. No statistically significant differences were found for low birth weight, respiratory distress or congenital abnormalities among the groups.

The authors postulate that the increased risk of hemorrhage in mothers with asthma could be related to coagulation changes associated with asthma and may be independent of medication and other factors. The increased risks of hypertension and hyperbilirubinemia could be related to asthma or to the use of steroids. They note with concern the clustering of risk factors in mothers with asthma who were not receiving asthma medication.