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Despite significant advances in neonatal-perinatal medicine, numerous challenges remain in the care of preterm infants. This is particularly true regarding those born at the lowest end of the gestational age (GA) spectrum, i.e., below 24 weeks GA, a group in which science is limited, and data from randomized controlled trials almost non-existent. The aim of this thesis was to evaluate selected aspects of early management - from the delivery room through the first weeks of postnatal life. The aspects were chosen based on their relative importance in initial preterm infant care and included endotracheal intubation, and fluid, glucose, and nutritional balances. We evaluated hospital outcomes, as well as brain MRIs performed at term, and later neurodevelopment.

Study I examined delivery room placement of endotracheal tubes (ETT) and umbilical catheters (UC) in seventy-five infants born at 22-23 weeks GA. A lower birth weight was associated with too deep ETT placement (p=0.018). Optimal median (IQR) depths found were: ETT 5.5 (5.5–6.0), low arterial UC 6.0 (5.5–6.5), high arterial UC 9.6 (9.2–10.3), and venous UC 5.5 (5.0–6.1) cm. ETT position was not associated with respiratory outcomes. The data imply that standardized use of the suggested GA-based depths of insertion for both ETT and UC would result in correct tip placements.

Study II analyzed fluid balance trajectories in sixty-seven infants born at 22-23 weeks GA. Hypernatremia (>150 mmol/L) occurred in 42%, and hyperglycemia (>10 mmol/L) in 87%. A postnatal weight loss exceeding 15% as well as the occurrence of acute injury was found to be independently associated with a several-fold increased mortality risk.

Studies III and IV consisted of the same study cohort of infants born extremely (GA 22–27 weeks, n=69), and very (GA 28–31 weeks, n=72) preterm. In Study III we investigated the associations between early hyperglycemia, and brain MRI and neurodevelopment at 2 years. We found a high (55%) incidence of early hyperglycemia (>10 mmol/l) in infants born at <28 weeks GA, that was independently associated with both lower white matter volume, and poorer neurodevelopment at 2 years.

Study IV looked at the impact of macronutrient intake on the same outcomes as above. Individual variations in macronutrient intake were not found to be associated with either neonatal brain growth, or later neurodevelopment, a finding which might be related to the fact that all infants had received intakes aligning with current recommendations.