in a Danish birth cohort study.
The reason behind the correlation is unclear. Maternal infections, rather than antibiotics, “could explain the observed association,” said study author Cecilie Skaarup Uldbjerg, a researcher in the department of public health at Aarhus University in Denmark.
Still, the “results are in keeping with the hypothesis that effects of antibiotics impact the maternally derived microbiome in vaginally born children and that this may increase the odds of childhood asthma,” Ms. Uldbjerg and coauthors wrote in their study, which was published online Feb. 9 in Archives of Disease in Childhood . “However, this observational study did not address underlying mechanisms, and this interpretation, while plausible, remains speculative.”
Antibiotic use in pregnancy likely to continue
Patrick Duff, MD, who was not involved in the research, does not expect the findings will alter clinical practice.
Dr. Patrick Duff
The association was relatively weak, and the study does not account for factors such as antibiotic exposure during early childhood or tobacco smoke in the house, said Dr. Duff, professor of maternal-fetal medicine at University of Florida, Gainesville.
“Although I agree that we should not use antibiotics indiscriminately during pregnancy, we definitely need to treat certain infections,” Dr. Duff said. “Thus we cannot avoid some degree of antibiotic exposure.”
Although prior research has indicated that antibiotic use in pregnancy may increase the risk of asthma in children, results have been inconsistent.
To study whether antibiotic exposure during pregnancy is associated with childhood asthma and whether the timing of antibiotic exposure or mode of delivery influence the relationship, the investigators analyzed data from more than 32,000 children in the Danish National Birth Cohort, which was established in 1996.
Children of mothers who took and did not take antibiotics compared
In all, 17% of the children were born to mothers who used antibiotics during pregnancy. Compared with mothers who did not take antibiotics, those who did reported more maternal asthma, smoking during pregnancy, and having overweight or obesity. In addition, they were less likely to have been in their first pregnancy.
During follow-up at age 11 years, 4,238 children (13%) had asthma, including 12.7% of those whose mothers had not been exposed to antibiotics, and 14.6% of those whose mothers had used antibiotics during pregnancy.
In adjusted analyses, children born to mothers who received antibiotics were more likely to have asthma (OR, 1.14).
Antibiotic exposure in the second to third trimester, but not in the first trimester, was associated with asthma. The association was observed in vaginally born children, but not in children born by cesarean section.
The study is limited by its reliance on maternal reporting for data about antibiotics and asthma diagnoses, the authors noted. Mothers completed telephone interviews twice during pregnancy and once at 6 months postpartum. They completed online questionnaires to provide follow-up information at 11 years.