Metabolic differences between AGA- and SGA-infants of very low birthweight. I. Relationship to intrauterine growth retardation.

Metabolic response to human milk feeding was studied in 12 appropriate (AGA) and 12 small for gestational age (SGA) infants of very low birthweight (VLBW) on the eighth day of life. Protein intake ranged from 1.98 to 2.47 g/kg/day and caloric intake from 94 to 126 kcal/kg/day with no significant differences between the groups. Alpha-amino-nitrogen, the total bile acid concentration in serum and total- as well as alpha-amino-nitrogen excretion in the urine were estimated. The alpha-amino-nitrogen and the total bile acid concentration in serum increased with increasing degree of intrauterine growth retardation. Also renal total- and alpha-amino-nitrogen excretion increased significantly in relation to the degree of intrauterine growth retardation. Thus, despite a relatively low protein intake in severely growth retarded VLBW-infants, metabolic changes could be found similar to those observed in AGA-infants on high protein intakes. The data suggest that during the first weeks of postnatal life VLBW-infants with intrauterine growth retardation have a decreased capacity to utilize or to metabolize protein when compared to AGA-infants with comparable birthweights. These metabolic differences have to be considered in the nutritional management of VLBW-infants.