The pathogenesis of malnutrition for preterm infants is multifactorial, relying on their well-being in utero and on their clinical course in NICU. Notably, intrauterine growth restriction may cause malnourished preterm neonates. Subsequent complications of prematurity, like infection or feeding intolerance, may worsen malnutrition or lead to extrauterine growth restriction (EUGR). 

Neonatologists aim to reach full enteral feeding as soon as possible to avoid complications of parenteral nutrition (that include sepsis and cholestasis) in premature neonates. 

Simultaneously, they aim to gain optimal growth corresponding to "in utero growth" patterns and treat feeding intolerance to avoid necrotizing enterocolitis. However, these aims still need to be achieved together.

Furthermore, giving human milk is crucial in this population as it promotes feeding tolerance and prevents NEC, apart from other well-known benefits of human milk.

Capasso L, Raimondi F. Nutrition of the Premature Neonate: Physiology, Pathology and Management of the Immature and Developing Gut. Front. Pediatr. 2022. doi: 10.3389/fped.2022.1039153