EFFECT OF INTRAUTERINE GROWTH-RETARDATION ON POSTNATAL WEIGHT CHANGE IN PRETERM INFANTS

To investigate the cause or causes of early postnatal weight change, w e measured total body water and fluid and energy balances in 14 preter m infants who were appropriate in size for gestational age (AGA) and i n 5 weight-matched, preterm, small-for-gestational-age (SGA) infants. On the first day of life, AGA and SGA infants had the same weight and total body water content. At 6 +/- 2 days (mean +/- SD), AGA infants h ad had significant weight loss (94 +/- 45 gm) and body water loss (67 +/- 80 ml), whereas weight and total body water content in the SGA inf ants at the same age (5 +/- 1 days) did not differ from the values at birth. Loss of weight and total body water in AGA infants was accompan ied by a greater diuresis than in SGA infants at the same amount of fl uid intake. At the end of week 1, AGA and SGA infants had the same tot al energy expenditure (184 +/- 33 vs 171 +/- 17 kJ . kg-1 . day-1); en ergy intake, which had exceeded total energy expenditure from the thir d day of life and beyond, already provided 188 +/- 46 (AGA) or 209 +/- 109 kJ . kg-1 . day-1 (SGA), respectively, for energy storage. Nitrog en balance was positive. Subsequent weight gain occurred at the same r ate in AGA and SGA infants; both total body water and solids increased . Energy intake, total energy expenditure, and the amount of energy st ored (measured during stable weight gain on a regimen of full enteral feedings) had significantly increased compared with week 1, but both g roups maintained similar energy storage. We conclude that the initial weight loss in infants is caused by a contraction of body water that d oes not occur in SGA infants; both groups have a subsequent weight gai n ot the same rate, with similar proportional increase in total body w ater and solids.