Growth Observational Study

Previous growth curves for premature infants were based on a 1948 study of 100 infants. More recent reports described growth rates for VLBW infants exceeded those predicted by the previous study. The authors suggested that the differences may reflect changes in nutritional management and cautioned that the observed growth rates may not be optimal. Although a greater number of extremely low birth weight infants were included in these studies, data for infants with birth weights <750 g was still limited.

This study was a multicenter, prospective cohort study to define postnatal longitudinal growth for very low birth weight (VLBW) infants. The objectives were: 1) to develop postnatal growth curves for VLBW preterm infants that would permit an assessment of growth velocity; 2) to relate growth velocity and nutritional practices (duration of parenteral nutrition, age at first enteral feeding, and age at full enteral feeding); 3) to compare growth velocity in infants who are small-for-gestational age (SGA) with infants who are appropriate-for-gestational age (AGA); and 4) to relate growth velocity to several common, major morbidities, including chronic lung disease (CLD), nosocomial infection (or late-onset infection) and necrotizing enterocolitis (NEC). These growth data may be useful in identifying preterm infants who are growing slowly despite current nutritional support and in designing and performing clinical trials of nutritional interventions.

Data were collected on 1660 infants with birth weights between 501 to 1500 g who were inborn or admitted at 24 hours of age or less to 1 of the 12 National Institute of Child Health and Human Development (NICHD) Neonatal Research Network centers between August 31, 1994 and August 9, 1995, survived >7 days (168 hours) and were free of major congenital anomalies. Infants were weighed daily for a minimum of 14 days or until birth weight was regained, whichever occurred later, and then weekly. Recumbent length was measured weekly with a Premie Length Board. Head circumference (HC) was measured weekly. Midarm circumference (MAC) was measured weekly. Length, HC, and MAC measurements were each performed twice.

Inclusion criteria

• Infants with birth weights between 501 to 1500g who were inborn or admitted at 24 hours of age or less
• Survived >7 days (168 hours)

Exclusion criteria

• Major congenital anomalies