[Labor contraction-dependent changes in magnesium and calcium in the myometrium]

Magnesium is commonly used in the therapy and prevention of preterm labor. Therefore the differences of the concentrations of magnesium and its antagonist calcium were measured in the human myometrium to examine the interaction of labour and ionic changes. The ionic concentration in the myometrium of 37 patients without labour are determined and the values are compared to the data of 26 patients in active labour. Women of the first group without labour had a magnesium concentration of mean = 4.1 mmol/kg wet weight and a calcium concentration of mean = 2.9 mmol/kg wet weight. Women of the second group with active labour have a significantly lower (p < 0.01) magnesium concentration (mean = 3.5 mmol/kg wet weight). However, the calcium level (mean = 2.7 mmol/kg wet weight) does not show significant differences. These results indicate that the decrease of magnesium plays an important role in the physiology of parturition. A low magnesium concentration in the myometrium might have a considerable influence on premature labour in the third trimester of pregnancy. Therefore a prophylactic application of magnesium seems to be useful.