Babies born vaginally emerge bathed in their mothers’ beneficial microbes, which may help their newly formed immune systems tell the difference between helpful and disease-causing bacteria. Babies born by cesarean delivery, or C-section, bypass that step. Now researchers believe that swabbing C-section babies with their mothers’ birth fluid may partially restore baby’s bacterial defense. This is the finding of a pilot study co-led by researchers from NYU Langone and published in the journal Nature Medicine.

The study revolves around the microbiome, the set of bacterial species that live on and in human skin, mouths, and guts. Such microbes evolved over millions of years to play roles in human digestion, metabolism, and immunity.

C-sections interrupt the “education” provided by the microbes that come with vaginal birth. Past studies have linked such interruptions with increasing rates of asthma, autoimmune diseases, and obesity. 

“Our study is the first to demonstrate that partial microbiome restoration just after birth is possible in babies born by C-section,” lead study author and NYU Langone microbiologist Maria Dominguez-Bello, PhD, tells The New York Times. “With a third of U.S. babies now born by C-section, twice the number as is medically necessary, the question of whether a baby’s founding microbiome affects its future disease risk has become more urgent,” says Dr. Dominguez-Bello.

Read more from The New York Times.