The goal of this clinical trial is to learn about the impact of donor milk vs formula supplementation on human milk feeding and the health outcomes of infants who require supplementation in well-baby units. It aims to explore whether supplementation with donor milk vs formula for infants during the initial hospital stay in a well-baby unit will increase both the exclusivity and duration of breastfeeding at 4 months. The Investigators will also explore whether the type of supplementation will positively affect measures of newborns' health, growth, behavior, feeding efficacy, and parental stress. Each participating infant born to a diabetic mother OR born small for his/her gestational age (<2500 grams) OR late preterm (35 0/7-36 6/7 weeks of gestational age) is assigned at random to 2 groups. The groups are: 1) Donor milk: all babies in this group will receive pasteurized donor milk from a trusted milk bank. 2) Formula: all babies in this group will receive formula as a standard of care.

Background and Importance: Human milk is the ideal nutrition for all infants, and research has demonstrated that human donor milk can provide health benefits for preterm infants. Approximately 35-50% of late preterm and term infants admitted to a well-baby unit after birth require supplementation due to various reasons including hypoglycemia, weight loss, or insufficient availability of parent's milk. However, there is limited research to guide decision making on which supplement to prescribe. Despite this, many hospitals are introducing donor milk in well-baby units in light of the growing recognition of the health protective effects of human milk.

Goals/ Research Aims: The primary research aim of this study is to compare the effects of supplementing parent's milk with donor milk versus formula in infants at increased risk for supplementation (infant born to a mother with diabetes, infant with a birth weight smaller than expected for the gestational age (SGA)) on exclusive human milk feeding at 4 months of age. Secondary research aims include: examining the effects of supplementing parent's milk with donor milk on any or exclusive human milk feeding rates at 1, 2 and 3 months, infant health and growth at hospital discharge and at 1, 2, 3, and 4 months, and breast feeding self-efficacy scores. Exploratory outcomes include: infant temperament scores at 1, 2, 3, and 4 months, and parental mental health scores at 2 and 4 months using validated questionaires, milk cortisol concentrations at 2 and 4 months, the use of informally shared milk, and the associated financial costs of a donor milk program versus formula.

Methods/ Approaches/ Expertise: This proposed study is a randomized, controlled, single-center trial that will involve assigning participants to two intervention arms (n=56 infants/arm). The intervention will involve providing donor milk or formula in bottles and will last for the duration of the infant's initial hospitalization, followed by monthly phone calls and a virtual or in-person assessment at 4 months. At each time-point of 1, 2, 3, and 4-month, surveys of breast feeding self-efficacy, and health and infant temparement will be conducted, and the infant's anthropometrics will be measured. Additionally, measures of parental depression, anxiety and stress will be assessed with survey-based tools at 2 and 4 months. A coincident human milk sample will be collected at 2 and 4 months and will be analysed for cortisol concentrations. The research team has experience running feeding interventions and donor milk trials in newborns, and includes experts in nursing, medicine, dietetics, and milk banking.

Expected Outcomes: This proposed research holds the potential to make a meaningful impact on public health. In Canada, with approximately 350,000 level I nursery admissions each year and high rates of formula supplementation ranging from 35-50%, there is a clear opportunity for improvement. By promoting exclusive human milk feeding, exploring evidence-based practices to inform hospital guidelines, and reducing the reliance on informal milk sharing, this research aims to enhance the health outcomes for both parents and infants. Additionally, it seeks to deepen the understanding of early parent-child interactions, fostering greater awareness and knowledge in this area.

Inclusion Criteria:

Infants admitted to the well-baby unit at Sinai Health whose parent(s) intend to feed parent milk and who require supplementation:

• Infants of gestational/ type 1/ type 2 diabetic mothers
• Infants who are born small for gestational age (SGA) by using a sex-specific reference population and determining if their birth weight falls below the 10th percentile for gestational age
• Infants with a birth weight less than 2.5 kg
• Late preterm infants born between 35 0/7-36 6/7 weeks of gestational age

Exclusion Criteria:

• Enrollment in any other clinical study affecting nutritional management during the feeding intervention; anticipated change in primary caregiver (person providing the feed) prior to 4 months; refusal to consent to donor milk; supplementation with formula prior to enrollment; any physical condition that may impact growth (ex: skeletal dysplasia).

All information collected during this study, including individual participant's personal health information, will be kept confidential and will not be shared with anyone outside the study unless required by law. Participants will not be named in any reports, publications, or presentations that may come from this study.