This article is part of MPR‘s coverage of the American Thoracic Society’s International Conference, taking place in San Diego, California. Our staff will report on medical research related to asthma and other respiratory conditions, conducted by experts in the field. Check back regularly for more news from ATS 2018.

SAN DIEGO — Frequent maternal antibiotic use during pregnancy is associated with increased risk for childhood asthma, according to data presented at the American Thoracic Society (ATS) 2018 International Conference, held May 18 to 23, 2018, in San Diego, California.

Researchers from Vanderbilt University Medical Center in Nashville, Tennessee, examined the association of timing, frequency, and class of antibiotic use during pregnancy on the development of childhood asthma in a large, population-based cohort. A total of 84,880 mother-child dyads from the Tennessee Medicaid Program were included in the study. Children were term, non-low birth weight, and otherwise healthy (52% boys; 54% white; 44% black). The investigators defined antibiotic use during pregnancy by the number of courses and class, and determined asthma risk by trimester-specific antibiotic use.

The results showed that approximately 66% of mothers received at least 1 course of antibiotics during pregnancy, and 14% of children developed asthma by 6 years. In addition, an increased number of courses of antibiotics (2 vs 0) increased the odds of having asthma by 30%.

The investigators found that children whose mothers used antibiotics only during the first trimester or during more than 1 trimester increased the likelihood of developing asthma by 11% (adjusted odds ratio [aOR], 1.11; 95% CI, 1.03-1.19) or 13% (aOR, 1.13; 95% CI, 1.03-1.24), respectively, after adjusting for number of antibiotic courses and covariates.

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Among children whose mothers used at least 1 course of antibiotics during pregnancy, later administration of the first course of antibiotics was associated with lower risk of developing childhood asthma (173 days vs 41 days; aOR, 0. 80; 95% CI, 0.75-0.86), but the protective association appeared to reverse after 200 days.

The researchers found no significant association between use of broad vs narrow antibiotics and childhood asthma development.

“The mechanisms through which antibiotics lead to increased asthma need to be understood to be able to develop effective prevention strategies,” they concluded.

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Turi KN, Gebretsadik T, Ding T, et al. Maternal antibiotic use during pregnancy is associated with childhood asthma: results from a large population study. Presented at: American Thoracic Society 2018 International Conference; May 18-23, 2018; San Diego, CA. Abstract A4194.

This article originally appeared on Pulmonology Advisor