Factors Associated With Growth of Extremely Premature Infants During Initial Hospitalization

Abstract

Objective. To quantify the factors associated with growth of very small premature infants during initial hospitalization. Population. Study patients were 109 infants who were appropriate for gestational age, weighed <1000 g at birth, and were fed intravenous hyperalimentation then calcium-supplemented 81-kcal preterm formula according to a protocol. Analysis. Multiple regression analysis was performed for periods of 0 to 56, 0 to 14, and 15 to 56 days of age. Growth was determined as change in weight during the period. Variables assessed in the initial model were caloric intake, protein intake, respiratory support duration, patent ductus arteriosus, dexamethasone use, infection, birth weight ratio (weight divided by expected intrauterine weight for gestation), gestational age, sex, calendar time from study start, maternal betamethasone administration, and necrotizing enterocolitis. For the 0 to 14-day period, maximum oxygen requirement for respiratory distress syndrome replaced respiratory support duration, and 5-minute Apgar score was added, whereas dexamethasone and necrotizing enterocolitis were deleted. Results. Mean change in weight was 785 g for 0 to 56 days, −16 g for 0 to 14 days, and 770 g for 15 to 56 days. Mean weight was 94% (13 SD) of mean intrauterine at birth, 73% (10 SD) at 14 days, and 73% (12 SD) at 56 days. Regression models explained 85%, 43%, and 80%, respectively, of variation in growth. Of the initial variables assessed, the following were the independent prognostic determinants of growth. There was a positive association with caloric intake at 0 to 56 days and 15 to 56 days, and with protein intake at 0 to 14 days. Negative associations were found for birth weight ratio and gestational age at 0 to 56 and 0 to 14 days. Respiratory support duration was negatively associated at 15 to 56 days, and dexamethasone was negatively associated at 0 to 56 and 15 to 56 days. Formulas to predict growth were established from the final regression models. Conclusion. The growth failure in appropriate-for-gestational-age, <1000-g birth weight infants can be related in part to dexamethasone use and respiratory support duration. Increasing caloric intake and early protein intake improves growth. However, for the majority of these patients, early losses are not corrected completely by 56 days using currently recommended intakes.