Altered Maternal Calcium Homeostasis in Diabetic Pregnancy*

Twenty-one diabetic gravidas were studied with serial measurements of serum concentrations of total and ionized calcium, magnesium, phosphorus, albumin, and parathyroid hormone and plasma levels of calcitonin. Pregnant diabetics had significantly lower serum magnesium concentrations throughout pregnancy than did nondiabetics. They also had significantly lower parathyroid hormone levels after midpregnancy, because the progressive increase in parathyroid hormone concentration observed in control subjects did not occur in diabetics. There was no significant difference between pregnant diabetics and nondiabetics in serum concentrations of total calcium, ionized calcium, phosphorus, or albumin or in plasma levels of calcitonin.