Postnatal adjustment in renal function.

Renal function was studied serially in 17 healthy term infants during the hours immediately following birth. Of 14 infants delivered vaginally eight received placental blood transfusion and six did not. The remaining three infants were delivered by cesarean section and received placental blood transfusion. Results indicate that the general pattern of change in urine output (V), clearance of inulin (CIN), and p-aminohippuric acid (CPAH), was similar in all infants despite a wide range in each of the functions measured. The pattern showed an initial increase in V, CIN, and CPAH followed by a decline to low values in all infants by 3 hours of age. Urine osmolality and output generally changed in opposite directions. During the first hour the values for V ranged from 0.02 to 0.47 ml/min; for CIN, from 0.5 to 9.1 ml/min; for CPAH, from 1.4 to 21.8 ml/min; and for osmolality, from 98 to 457 mOsm/kg. By 4 hours of age the values for V ranged from 0.01 to 0.15 ml/min; for CIN, from 0.8 to 3.7 ml/min; for CPAH, from 0.8 to 7.5 ml/min; and for osmolality, from 240 to 520 mOsm/kg. The initial values of V, CIN, and CPAH, as well as the changes, were greatest in those infants who received a placental transfusion; however, there were no statistical differences among the means of the various groups. By 4 hours of age, the range of values observed in the initial measurement was much less pronounced. This probably reflects the achievement of stability of renal circulation following adaptation to a variety of stresses during the intrapartum period.