The investigators propose to conduct an exploratory pilot study, enrolling 30 exclusively breastfeeding newborns 36-96 hours of age, whose Total Serum Bilirubin (TSB) is within 0.1-3 mg/dl of the American Academy of Pediatrics (AAP)-recommended treatment thresholds for Phototherapy (PT). These newborns will be randomly assigned to receive either 10 cc extensively hydrolyzed formula following each breastfeeding using cup, spoon or syringe, or to continue exclusive breastfeeding. Infants will be followed at 1, 2, 3 and 6 months to assess breastfeeding duration and use of formula and complementary foods. Our hypothesis is that limited, small amounts of formula administered without a bottle immediately following breastfeeding might reduce the incidence of severe hyperbilirubinemia among newborns at increased risk of TSB exceeding AAP-recommended thresholds for beginning phototherapy.