Children born after in vitro fertilization or intracytoplasmic sperm injection had a nearly three-fold increased risk of asthma, almost a doubled risk of wheezing and more than a quadrupled risk of taking asthma medications, compared to others in the study.
These findings held when the children reached age 7, although they were slightly reduced, the researchers noted.
To assure the strength of their findings, the researchers took into account the mothers' history of asthma, smoking status, weight, socioeconomic status, and whether they had pets, as well as the babies' gestational age at delivery, type of delivery and whether they were breast-fed.
Many possible explanations could account for the observed association between infertility problems and asthma, the researchers said. These include the severity of the infertility, infertility treatment, over-reporting of asthmatic symptoms by protective parents or other factors.
"This work adds to a small but growing body of evidence that suggests that children born after [assisted reproductive technologies] are more likely to experience childhood asthma," Carson said. "However, at this time we do not yet know if the observed association is causal, or the mechanism by which it acts. Further research is needed to establish what might be causing the association."
To learn more about in vitro fertilization, visit the American Pregnancy Association.
SOURCES: Claire Carson, researcher, National Perinatal Epidemiology Unit, University of Oxford, England: David Cohen, M.D., chief, reproductive medicine, and associate professor, obstetrics and gynecology, University of Chicago; Dec. 6, 2012, Human Reproduction, online
All rights reserved