Effect of Early Limited Formula on Total Serum Bilirubin Among Newborns With Hyperbilirubinemia

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.

Inclusion criteria Healthy infants ≥ 35 weeks Neonates 36-96 hours old Exclusively breastfeeding TSB 0.1-3 mg/dl below AAP-recommended PT threshold TSB < 6 hours ago Mothers English-speaking or Spanish-speaking Outcome Measures Primary outcome: Total Serum Bilirubin Secondary clinical outcomes: Phototherapy, hospital readmission, exclusive and partial breastfeeding at 1 week, 1 month, 2 months, and 3 months; breastfeeding self-efficacy

Participants will be instructed to continue exclusively breastfeeding with no formula supplementation.

Investigators will advise to supplement with 10cc's of extensively hydrolyzed formula immediately following each breastfeeding until TSB declines.

The investigators will compare measured TSB to AAP guideline recommendations for phototherapy treatment and confirming with Bili Tool, an automated program designed for this purpose.

Receipt of phototherapy and hospital readmission, exclusive and partial breastfeeding at 1 week, 1 month, 2 months, and 3 months; breastfeeding self-efficacy

The investigators will ask mothers whether the infant received any breast milk in the last 24 hours. For infants whose mothers state they have received breast milk in the last 24 hours, the investigators will ask mothers whether the infant received anything other than breast milk in the last 24 hours. The investigators will ask mothers whether the infant received anything other than breast milk since the prior assessment. The investigators will query subjects using the Breastfeeding Self Efficacy Scale, short form, at enrollment, 1week and at 1 month.

Inclusion Criteria: Healthy infants ≥ 35 weeks Neonates 36-96 hours old Exclusively breastfeeding TSB 0.1-3 mg/dl below AAP-recommended PT threshold TSB < 6 hours ago Mothers English-speaking or Spanish-speaking Exclusion Criteria: Infants who have already received formula Infants who have received or are receiving Level II or Level III Infants who have already lost ≥ 10% birth weight Infants with Glucose-6-phosphate dehydrogenase deficiency, positive direct antigen testing, cephalohematoma or other extensive bruising