Receiving breastmilk from a mother is linked to better metabolic and cognitive outcomes as well as lower rates of newborn morbidity in preterm infants. Yet, a lack of supplies makes the use of pasteurized human milk or bovine formula necessary.

Randomized clinical studies (RCTs) that have identified the best supplement for newborns when the mother’s milk supply is limited are still lacking in this area. Infants exclusively fed human donor milk experienced lower incidences of necrotizing enterocolitis (NEC) than infants exclusively fed formula. In studies when formula was just used as a supplement, this difference, however, was not statistically significant.

Breast milk may minimize the risk of NEC through a variety of causes, including the absence of bovine antigens that could trigger an allergic reaction in the baby. Furthermore, the gut microbiota may potentially benefit from the presence of some functional components in breast milk, such as lactoferrin and human milk oligosaccharides (HMOs).

Researchers in the current RCT examine the impact of a diet consisting solely of human milk on preterm infants’ gut microbiomes. In this study, only breastmilk-fed preterm newborns from four NICUs in the United Kingdom were chosen for inclusion within 72 hours of birth. Infants with life-threatening congenital problems were not included.Infants were randomized to intervention (exclusive human milk diet) and control (standard diet) arms. Feeding in the control arm included using the mother’s breastmilk and preterm formula milk to compensate for the shortfall in breastmilk supply. Infants in the intervention arm were fed breastmilk and a pasteurized human milk product to make up for the breastmilk shortfall.

Control group infants received a bovine-derived fortifier, whereas those in the intervention arm received a human milk-derived fortifier. Infants continued to receive their assigned diets until 34 weeks post-menstrual age (PMA).

Morbidity and weight gain data were obtained until discharge. Then, data on demographics and outcomes were captured using medical records and the National Neonatal Research Database.