Creatinine, urea and uric acid in amniotic fluid, maternal and umbilical cord blood at delivery.

Amniotic fluid, maternal vein serum and umbilical cord serum were obtained almost simultaneously from 31 women after an uneventful course of pregnancy. Specimens of amniotic fluid contaminated by blood or meconium were excluded. Creatinine, urea and uric acid were measured by autoanalyser techniques. The concentrations of creatinine, urea and uric acid in amniotic fluid were significantly higher when compared with the levels in maternal vein serum or umbilical cord serum. Between maternal and umbilical cord serum there were only small or no differences. The linear correlations of creatinine, urea and uric acid between maternal and umbilical cord serum were greater than those between amniotic fluid and maternal serum of amniotic fluid and cord serum. It is suggested that the high levels of creatinine, urea and uric acid in amniotic fluid are primarily determined by fetal urine.