Plasma amino acid concentrations in umbilical cord vein and artery of newborn infants after elective cesarean section or spontaneous delivery.

Twenty-four infants delivered by elective cesarean section and 23 spontaneously born infants were studied for plasma amino acid concentrations of the umbilical cord vein and artery. Normal labor was not found to influence plasma amino acid concentrations. In both spontaneously and operatively born infants, similar venous-arterial gradients were found for all essential and five nonessential amino acids. Based on the differences of venous and arterial concentrations and the umbilical cord blood flow, the daily fetal retention of single amino acids was calculated.