DOnor Milk to REpair the Full-term Infant MIcrobiome in Infants Born Via Cesarean Section.

Investigators propose to conduct a pilot clinical RCT in the postpartum hospital setting examining DHM as an intervention provided to full-term infants delivered via caesarean section. Randomization of participant infants is currently an ethical practice because DHM supplementation is not standard practice in this population; infants receive formula if supplementation of mother's own milk (MOM) is required. Additionally, randomization will allow investigators to determine causal relationships between DHM supplementation compared to formula supplementation on the infant gut microbiome. Finally, conducting research in the clinical setting will allow for pragmatic assessment of DHM as an intervention, enhancing external validity and increasing the likelihood of its implementation into healthcare systems to improve healthcare quality. Population: The population of interest is caesarean section born, full-term infants whose mothers are planning on breastfeeding. Recruitment: Mothers greater than 37 weeks' gestation in the labour and delivery or postpartum unit who deliver via caesarean section will be screened for participation in the study by nurses on the postpartum and labour and delivery units. Upon recruitment and completion of informed consent, infants requiring supplementation of MOM will be randomized to the control or intervention group. Investigators will randomize 90 mother-infant dyads, providing adequate power to detect overall microbiome differences (\~45 in each group). Intervention - Donor Human Milk (DHM) - Infants randomized to the intervention group will receive DHM each time supplementation is required for the first 7 days of life. The exposure time of 7 days was selected due to feasibility of DHM cost, and this is the period when breastfeeding is being established and most formula supplementation occurs. Infants in the control group will receive formula when supplementation is required (standard care). All DHM in North America is pasteurized and provided through certified milk banks regulated by the Human Milk Banking Association of North America and DHM for this study will be obtained from the NorthernStar Mothers Milk Bank (NMMB). Data Collection, Analysis, and Outcomes: The primary outcome for this pilot study will result from comparisons of DHM to formula supplementation groups for differences in microbiome signatures, such as diversity, proportions of Bifidobacteria, and proportions of pathogenic organisms. Infant stool samples will be collected from soiled diapers at one week, 3 months and 6 months postpartum. Secondary outcomes include infant growth, sleep, and breastfeeding outcomes that will be collected at one week, 3 months and 6 months postpartum.