Pilot Study of the Feasibility of Feeding Preterm Infants With Fresh Versus Frozen Mother's Own Breast Milk in the NICU

Background Necrotizing enterocolitis (NEC) is a severe inflammatory disorder of the intestine that primarily affects very low birth weight (<1,500 g)/very preterm infants (≤32 weeks' gestation); it is also the leading cause of death in the neonatal intensive care unit (NICU). The incidence of NEC (≥stage 2) in very preterm infants across Canada is 5% and increases as gestational age at birth decreases, with an incidence of 13% in infants born at <25 weeks' gestation and 10% in infants born at <29 weeks' gestation. Overall mortality from the disease has been reported to range from 15 to 30%, with more severe cases of NEC having a higher mortality rate.For infants who survive there is a significant risk of long-term complications and morbidity including neurodevelopmental issues.

Currently there is no known effective treatment for NEC. Infants are initially managed medically through bowel rest (cessation of oral feeds), abdominal decompression, administration of broad spectrum antibiotics, and provision of supportive care including parental nutrition, ventilator support, and blood transfusions as necessary. Should bowel perforation occur then surgery is required to remove damaged tissue and gas build up through laparotomy and/or primary peritoneal drainage.

Perhaps the best form of treatment for NEC is prevention. Mother's breast milk is best for preventing NEC. Breast milk contains both nutritional components (proteins, amino acids, fats, carbohydrates, vitamins, and minerals) and bioactive components (macrophages, T cells, cytokines, hormones, and growth factors) that have antimicrobial and anti-inflammatory properties. More recently, Hassiotou4 showed that breast milk is also a rich source of pleuripotent stem cells that when ingested by the infant, enter the blood stream and are incorporated into major organ systems in the infant. Although their function is unknown, it is possible that they benefit the infant through growth or regeneration. The evidence strongly suggests that fresh breast milk may have a protective effect against both infection and NEC. When mother's own breast milk is not available the options are donor breast milk or formula. The use of formula in low birth weight/preterm infants has been reported to increase the risk of developing NEC when compared with donor breast milk.

However, current practices related to handling and use of human milk raise questions about whether we are deriving maximum benefit from their use. Currently, in the standard neonatal intensive care unit (NICU) breast milk expressed by mothers of preterm infants is frozen and stored in the milk bank. When the infant requires oral feeds an order is placed with the milk bank, the oldest batch of milk defrosted, fortifier added as needed, and the milk then sent to the NICU for use. The act of freezing breast milk,either at -20°C or -80°C, along with the passage of time decreases the energy content and reduces the levels of several of the most useful components in the milk, including fat, carbohydrate,secretory immunoglobulin A,lactoperoxidase,lysozyme, antibacterial factors,and antioxidants. In addition to the decrease in these components, any stem cells in the milk have a half-life of 4 hours, so the defrosted milk does not contain any stem cells.

The current NICU breast milk feeding procedure exists as a means of ensuring that infants have consistent access to their mother's breast milk even if the mother is not able to spend time in the NICU. The process also allows for stricter quality and infection control, as well as computerised inventory and monitoring via electronic health records.However, the process deprives infants of the benefits of the cellular content of breast milk, including the stem cells.