Fetal umbilical venous-arterial differences of citrate in the chronically catheterised sheep.

Whole blood citrate concentration was measured simultaneously in the umbilical vein, fetal femoral artery and maternal artery in seven chronically catheterised pregnant ewes and their fetuses. The mean citrate concentration was 0-321 mmoles/litre in the umbilical vein, 0-297 mmoles/litre in the fetal femoral artery and 0-095 mmoles/litre in the maternal artery. The mean concentration difference for citrate across the fetal placental circulation was 0-024 mmoles/litre but this was not statistically significant (P less than 0-1).