Is use of antibiotics in infancy tied to childhood obesity? Some studies suggest so, but a new analysis suggests the link may be with infections, rather than antibiotics.

Using records of a large health maintenance organization, researchers tracked 260,556 infants born from January 1997 through the end of March 2013. The database included details on antibiotic use, diagnosis and height and weight measurements from birth through age 18. The study is in Lancet Diabetes and Endocrinology.

The scientists compared children who had no infections and no antibiotic use in the first year of life with those who had untreated infections. They found that an infant with one untreated infection had a 15 percent increased risk for childhood obesity, and the risk increased to 40 percent in those with three untreated infections.

But there was no difference in obesity risk between infants treated with antibiotics and those with a similar infection left untreated. In other words, infections, but not the use of antibiotics, were associated with childhood obesity.

“If there is an infection during infancy, particularly a respiratory or ear infection, it should be treated,” said the lead author, Dr. De-Kun Li of the Kaiser Permanente Division of Research. “You shouldn’t avoid antibiotics because you are concerned about childhood obesity.”