Vaginal Microbiome Exposure and Immune Responses in C-section Infants

The purpose of this research study is to assess at how differences in the microbiome (naturally occurring bacteria) of a baby may protect, or put a baby at risk, for allergic problems. The microbiome refers to the thousands of bacteria and molds that live in and on our bodies. The microbiome plays an important role in our health. Differences in the microbiome can affect our immune system in ways that might make some people more likely to get allergies and asthma. Early life events and exposures are very important for establishing the human microbiome. The newborn baby's microbiome changes very quickly during the first weeks and months of life. There is information that suggests C-section birth is associated with higher risk of certain diseases, including allergies and asthma. Some researchers think one reason for this is that passing through the mother's vaginal canal during birth exposes the baby to bacteria that promote healthy immune system development, something that C-section babies don't get. Transferring these potentially beneficial vaginal bacteria to C-section babies may help prevent some diseases later.

This is a pilot study of 120 pregnant women and their infants conducted at hospitals in the Mount Sinai Health System in New York, NY. Eighty women will deliver via elective, unlabored C-section, and 40 will undergo spontaneous vaginal delivery. The 80 women undergoing C-section will be randomized in a masked (blinded) 1:1 fashion to have their neonates undergo vaginal seeding or placebo seeding immediately after birth (within 10 minutes) followed by standard care.The infants of the 40 women undergoing spontaneous vaginal delivery will receive usual standard care. All 120 pregnant women will have biospecimens collected to assess their vaginal, skin, gut, placental, breast milk, and oral microbiome. All infants will have biospecimens collected to assess their gut, skin, nasal, and oral microbiome, as well as blood to assess allergen sensitization and immune markers. Infants will be followed with at-home stool collections and questionnaires weekly for the first 4 weeks and at weeks 8, 26, and 39. An in-person study visit will occur at 13 weeks and 52 weeks, and the primary endpoint will be assessed at 52 weeks. Study enrollment is projected to occur over 24 months.