Objective: To study the characteristics of the infants born to women who have used anti-asthmatic drugs during pregnancy.
Material and methods: Various characteristics of infants with mothers who had reported the use of anti-asthmatic drugs in early pregnancy (n=24,750) or had such drugs prescribed later during pregnancy by a maternity health care centre (n=763) were identified from the Swedish Medical Birth Register and compared to those of all infants. Risks estimated with Mantel-Haenszel technique were expressed as odds ratios (OR) with 95% confidence intervals after adjustment for a number of putative confounders. The severity of maternal asthma was assessed on the basis of the number of anti-asthmatic drugs used.
Results: An increased risk for preterm birth, low birth weight and small for gestational age was found, which increased with the number of anti-asthmatic drugs used by the mother during pregnancy (OR=1.46, 1.67, and 1.70, respectively, when three or more drugs had been used). An increased risk for large for gestational age could be explained by the effect of gestational diabetes and high body mass index. An increased risk for neonatal icterus was mainly an effect of preterm birth, while an increased risk for respiratory problems and/or low Apgar score (OR=1.43) was only slightly reduced in full-term infants. An increased risk for hyperglycaemia (OR=1.62) was not explained by confounding from maternal diabetes. No risk increase was found for neonatal convulsions or cerebral haemorrhage. Mortality was increased only among infants whose mother had used three or more anti-asthmatic drugs (OR=1.52).
Conclusion: Infants whose mothers had asthma had a number of manifestations of poor outcome which appeared to be linked with the severity of the asthma.