Objective: To study the risk for congenital malformations among infants whose mothers used anti-asthmatic drugs during pregnancy.
Materials and methods: We studied 24,750 infants whose mothers reported the use of anti-asthmatic drugs in early pregnancy. Infants were identified from the Swedish Medical Birth Register where drug use reported at the first maternal health care visit is recorded. Congenital malformations among the infants born were identified from that register, the Swedish Register of Congenital Malformations, and the Hospital Discharge Register. Rates of malformations among infants exposed to anti-asthmatics were compared with the background population rate of malformations (4.7%) after adjustment for year of birth, maternal age, parity, smoking, and previous miscarriages.
Results: A weak increase in the risk for a congenital malformation was seen (odds ratio =1.09, 95% CI=1.03-1.15) which could not be explained by the confounders studied. The risks for three specific types of malformations appeared to be increased: relatively severe cardiac defects, orofacial clefts and specifically median cleft palate, and anal atresia. For the two last mentioned groups, use of anti-asthmatics with inhaled corticosteroids showed a higher odds ratio than use of other anti-asthmatics, but the differences could be random.
Conclusions: Maternal asthma and use of anti-asthmatic drugs carry no major risk for congenital malformations in the offspring, but a slight teratogenic effect cannot be excluded. It may be due to asthma, and arguments for a stronger effect of inhaled corticosteroids than of other anti-asthmatics are weak.