Relationship of endogenous magnesium and calcium levels to oxytocin augmentation.

The relationship between plasma levels of magnesium (Mg) and calcium (Ca) and the plasma Ca to Mg ratios has been investigated in two groups of women. One group of 19 women required augmentation of labor with oxytocin and the control group of 50 patients had normal successful labor. The Mg levels in the plasma were significantly higher in those patients requiring oxytocin augmentation of labor and the Ca/Mg ratio was significantly lower. In the control group, 13 out of the 50 patients had Ca/Mg ratios below 3, whereas 13 out of 19 patients requiring augmentation of labor with oxytocin had Ca/Mg ratios below 3.