Althought biolectrical impedance (BIA) has been shown to be a predictor of total body water (TBW) in newborn infants, there are no longitudinal studies analysing the variation of TBW in growing premature infants.

Forty-six newborn infants with a gestacional age between 26 and 31 weeks were studied weekly from birth to term. Body weight, length, head circunference, triceps skinfold and mid-arm circunference were assessed weekly. BIA was performed with a body-composition analyser (model BIA-101 RJL Systems, Detroit) with a right-sided tetrapolar placement of electrodes as described by kushner et al (Am J Clin Nutr 1986:44, 417). Infants were divided in two groups and mean values were calculated for resistance, reactance and body weight.

There was an increase in resistance and reactance during the first 2 weeks after birth. After this period, when the pactients began to gain weight, all valves were, we observed a gradual decrease in resistance and reactance. At termcorrected age, values significantly lower than those observed at birth.

These data are the first longitudinal analysis of resistance and reactance in LBW infants. Our results may be useful to estimate changes in body composition during growth of preterm infants. Table

Table 1
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