Initial nutrition in preterm infants: Evidence, uncertainty, and research priorities.

Initial nutrition during the fetal-to-neonatal transition is critical for preterm infants and requires balancing physiologic adaptation, metabolic tolerance, and risk of morbidity. Although traditional approaches favored delayed enteral feeding with prolonged parenteral nutrition to protect the immature gastrointestinal tract, accumulating evidence supports earlier initiation of enteral nutrition and more selective use of parenteral nutrition based on gestational age, illness severity, and antenatal factors. This review synthesizes evidence guiding initial nutrition-defined as the period from birth to sustained full enteral feeding-with a focus on clinical application. We review enteral strategies including oropharyngeal colostrum administration, timing and volume of early feeds, duration of trophic feeding, early total enteral feeding, and feeding advancement rates, highlighting populations with robust evidence and those underrepresented in trials. Parenteral fluid practices are discussed in relation to physiologic postnatal weight loss, fetal growth restriction, and risks of both fluid overload and nutrient under delivery. We further address parenteral macronutrient and micronutrient provision, transition from parenteral to enteral nutrition, and limitations of peripheral parenteral nutrition delivery, noting areas reliant on expert consensus. We identify key evidence gaps and research priorities. Optimizing individualized initial nutrition strategies remains essential to improve growth, reduce morbidity, and support neurodevelopmental outcomes in preterm infants.