Second trimester calcium-phosphorus-magnesium homeostasis in women with threatened preterm delivery

The effect of threatened preterm delivery on calcium, phosphorus, magnesium homeostasis in the second trimester of pregnancy was investigated.

Serum concentrations of total and ionized calcium, inorganic phosphorus, magnesium, total protein, albumin, total estrogens and human placental lactogen were determined in women with threatened preterm delivery at 23-28 weeks of gestation (the studied group) and in women with uncomplicated pregnancy of the same duration (the control group). Additionally activities of total alkaline phosphatase and heat-stable alkaline phosphatase fraction were measured.

Patients of the studied group compared to the control group showed decreased concentration of total calcium (2.15 +/- 0.073 vs. 2.25 +/- 0.11 mmol/l, P < 0.001), inorganic phosphorus (1.21 +/- 0.26 vs. 1.34 +/- 0.22 mmol/l, P < 0.01) and magnesium (0.63 +/- 0.053 vs. 0.71 +/- 0.12 mmol/l, P < 0.001), total protein (64.0 +/- 5.4 vs. 68.6 + 1.0 g/l, P < 0.001), albumin (546.3 +/- 55.1 vs. 579.6 +/- 49.3 micromol/l, P < 0.003) and placental lactogen (3664 +/- 1806 vs. 4651 +/- 1858 ng/ml, P < 0.02); they also demonstrated decreased activity of total alkaline phosphatase (42.17 +/- 16.99 vs. 50.66 +/- 6.56 IU/l, P < 0.001) and its heat stable fraction (22.65 +/- 7.89 vs. 31.89 +/- 9.09 IU/l, P < 0.001). Patients of the studied group showed normal values of ionized calcium and total estrogens.

Premature uterine contractility in women in the second trimester is accompanied by lowered serum concentrations of total calcium, inorganic phosphorus, magnesium, total protein and albumin. There is also decreased activity of total alkaline phosphatase, its heat-stable fraction and placental lactogen which may have diagnostic value. Premature uterine contractility in women in the second trimester may be related to the disturbances of calcium-phosphorus-magnesium homeostasis and calcium supplementation should be considered.