[Analysis of renal water excretion in full-term newborn infants].

The response of renal water excretion was studied in 33 healthy 1-2 day-old and 6-7 day-old full-term newborn infants. With increasing milk intake (fluid intake) in 6-7 day-old newborn infants, there was not only a significant increase of urine flow, urinary sodium excretion was also significantly increased with urine amount (p < 0.01). There was no significant differences of serum osmolality and serum sodium between 1-2 day-old and 6-7 day-old newborn infants, but there was a significant decrease of urine osmolality (p < 0.01) in 6-7 day-old infants. It is suggested that following high fluid (milk) intake full-term infants are capable of adaptively excreting large urine volume and more dilute urine.