Nutritional requirements in preterm infants can be elevated, as a result of complex clinical circumstances including infections, immaturity of the gastrointestinal tract and invasive treatments, such as surgery which can place a greater metabolic demand on the body. Furthermore, these circumstances can impact an infant's ability to meet nutritional requirements and achieve optimum growth through normal feeding alone. Most preterm infants may need specialist care by the neonatal team during hospital admission and post-discharge, which includes enteral nutritional support.

Human Milk Fortifier (HMF) have become a component of the routine clinical care of preterm infants on neonatal units. There is published evidence to support this practice as being safe and effective. A multitude of trials have demonstrated improvements in weight, length and head circumference following interventions using HMF, compared to non-supplemented cohorts, and benefits have been observed at long term follow up.

Whilst HMF is used routinely in neonatal units, there is little clinical evidence for using them beyond discharge in the community, although this is widely accepted in practice. Nutricia have developed a new HMF (NHMF) that can be provided for use in the community.

This series of case-studies will evaluate the tolerance, compliance, acceptability and safety of the NHMF, in 15 preterm infants. Each case study will last at least 28 days, including at least 7 days in the community setting. The case studies will be conducted across multiple specialist neonatal centres in the UK, to meet the UK ACBS requirements.

Inclusion Criteria:

• Preterm infants fed own mother's milk (or donor human milk) requiring HMF (as decided by the investigator)
• Born before 37 weeks completed gestational age and >1 dropped centile since birth requiring HMF (as decided by the investigator)
• Tolerating adequate volume of enteral nutrition
• Expected to require HMF after discharge (minimum 4.0g NHMF per day at discharge)
• Written or electronic informed consent from parent/caregiver

Exclusion Criteria:

• Anticipated short term use of HMF leading to discontinuation of HMF after hospital discharge
• Presence of any relevant proven or suspected chromosomal anomaly or genetic syndrome, any gastrointestinal malformation/compromise, including Necrotising enterocolitis (NEC) (defined as Bell's stage two or higher), metabolic disorder, or congenital central nervous system malformation that may impact tolerance of enteral feeding
• Failure to establish enteral nutrition and requiring full parenteral nutrition
• Participation in other studies within 1 month prior to the entry of this study
• Known allergy to any of the study product ingredients, including cow's milk, fish and egg
• Concern or issues around the breast milk supply from mother of preterm infant at enrolment
• Investigator concerns around willingness/ability of the parent/caregiver to comply with protocol requirements and/or handle and store NHMF appropriately