This study will compare infant gut bacteria for infants who have been fed a standard infant formula (Enfamil Infant); infants who have been fed a new infant formula designed to be more similar to breast milk (Enfamil NeuroPro); and breastfed infants. These formulas are currently available on the market and meet FDA requirements for infant formula.

This study is a randomized, double-blind, parallel-group study comparing breast milk to Enfamil Infant and Enfamil NeuroPro formulas. The central hypothesis of the study is that the addition of milk fat globule membrane and2'-Fucosyllactose (2'-FL) to infant formula plays a role in shaping the microbiota in a manner similar to the microbiota of breastfed infants. To test this hypothesis, the investigators will explore longitudinal changes in the fecal microbiome from birth to 4 months of age in infants fed breast-milk, standard Enfamil Infant formula or Enfamil NeuroPro formula. Fecal samples will be collected at birth, and then monthly for 4 months. At the time of last collection one serum sample will be collected. The investigators will analyze basic growth parameters, fecal microbial community analysis by metagenomics, fecal metabolome by untargeted metabolomic analysis, and fecal and systemic indicators of inflammation and intestinal barrier function.

Inclusion Criteria:

• Healthy term infants with parental consent
• Parents are able to provide informed consent; own a smart phone and are able to fill out weekly digital questionnaires.

Exclusion Criteria:

• Prematurity (<= 36 weeks gestational age)
• Babies born through c-section
• Any health issues identified at the first postpartum screening
• Use of both breast milk and formula
• Use of donor breast milk
• Parent unwillingness/inability to avoid giving prebiotics, probiotics, symbiotics, and immune-stimulating products to the child for the duration of this study

Data and specimens will not be stored for future research.

Participants and research nurse/coordinator will be blinded to the formula assignment. The formulas used will be a standard infant formula (Enfamil Infant) and a new infant formula designed to be more similar to breast milk (Enfamil NeuroPro); both formulas are available for purchase by the public and meet FDA requirements for infant formulas. Each formula can (identical size) will be relabeled and coded by the investigators. Participants in the formula group will be provided with a four-month supply of powdered formula at the time of discharge from the hospital, along with stool collection kits.