Acid-base equilibrium in umbilical cord blood and time of cord clamping.

The present study was undertaken to determine the influence of the time interval between birth and the clamping of the umbilical cord on the acid-base balance of the newborn. At 30 seconds after birth, arterial blood from the unclamped cord showed a distinct decrease in pH and an increase in PCO2 and base deficit. These changes were not observed in the venous cord blood. The arterial blood changes continue during the first minute following delivery. When the cord is clamped immediately after birth, acid-base equilibrium in arterial and venous blood at 60 seconds after birth oscillates around the values obtained at zero time. When acid-base equilibrium of arterial cord blood is used as a parameter of neonatal well-being, immediate clamping seems mandatory.