The concentration of free calcium ions and total calcium in pregnancies at term

Abstract

The concentration of free calcium ions (cCa²⁺), total calcium (ctCa) and pH was measured in 46 normal pregnancies at term. Measured with a combined Ca²⁺-pH electrode system in whole blood, maternal plasma cCa²⁺ was 1.18 ± 0.03 mmol/l, and the corresponding plasma pH was 7.37 ± 0.05 (mean ± SD). In the cord vein, plasma cCa²+ was 1.44 ± 0.07 mmol/l and pH 7.37 ± 0.05. In the cord artery, plasma cCa²⁺ was 1.47 ± 0.07 mmol/l and pH 7.29 ± 0.07.

Key-words:

• active transport
• activity
• ion-selective electrodes
• ionized calcium-pH relation
• placenta