[Kidney function and electrolyte metabolism in healthy pregnant women].

In pregnant women alterations in kidney function, hormone, electrolyte and water metabolism are common findings. In 15 healthy pregnant women the kidney function and electrolyte metabolism were investigated during pregnancy and after delivery. The glomerular filtration rate measured by creatinine clearance was 20% higher in the I. trimester than in the II. and the III. trimesters and after the delivery. The sodium clearance was in the III. trimester significantly lower than in both the I. and the II. trimesters (p < 0.001, p < 0.01); the fractional sodium excretion was lowest in the third trimester. Furthermore the serum calcium concentration decreased significantly in the II. and III. trimester in comparison to the I. trimester (p < 0.01, p < 0.001), which was associated with a moderate increased urinary calcium excretion. The phosphate clearance increased during pregnancy and decreased approximately 50% after delivery (p < 0.01). The magnesium clearance was 40% higher in the third trimester in comparison to the I. trimester (p < 0.05) and 61% higher than the value post delivery (p < 0.01). The uric acid clearance during pregnancy was markedly increased and decreased 70% after delivery (p < 0.05). The results showed that in the III. trimester an intensive sodium retention occurred, which is associated with an increase of the plasma volume, interstitial fluid and body weight. The decreased serum calcium concentration in the II. and III. trimesters, the increased urinary calcium excretion as well as increased phosphate clearance suggest an increased parathyroid-hormone secretion.(ABSTRACT TRUNCATED AT 250 WORDS)