Carbohydrate intake is the main determinant of growth in infants born <33 weeks' gestation when protein intake is adequate

Objective: We investigated the relative contribution of macronutrients to postnatal growth in preterm infants born <33 wk of gestation. Methods: An audit of daily parenteral and enteral intakes of protein, carbohydrate, fat, energy, and growth (daily weight, weekly length, and head circumference) from birth to discharge home in 138 infants at <33 wk of gestation admitted to an Australian tertiary hospital was done. A mixed-model analysis of variance with random effects (slope and intercept) for subject and controlling for time, sex, gestational age, and total energy was used to determine the relative contribution of macronutrients to growth. Results: A higher energy intake (kilocalories per day) had a positive influence on growth. With total energy held constant, the contribution of carbohydrate to total energy had a positive relation to weight, length, and head circumference gains; protein had no relation and fat was negatively associated. For every 1% increase in energy from carbohydrate, there was a 2.3-g/d increase in weight (95% confidence interval 1.6-3.0, P < 0.0001), a 0.013-cm/d increase in length (95% confidence interval 0.003-0.022, P = 0.007), and a 0.015-cm/d increase in head circumference (95% confidence interval 0.009-0.022, P < 0.0001). Conclusion: A re-examination of the macronutrient balance in the diet of preterm infants is required in relation to optimizing growth.