The importance of maintaining dietary calcium intake and normal calcium metabolism for optimal regulation of arterial pressure in humans and experimental models has been demonstrated by us and other investigators. Recent reports have suggested that low dietary calcium intake and disturbances in maternal calcium metabolism may be associated with an increases in blood pressure during late gestation. These factors may be associated with an increase in the risk of developing pregnancy-induced hypertension. To explore this hypothesis, during year 1 of this proposal dietary calcium intake and biochemical markers of calcium metabolism will be assessed and compared during the 3rd trimester in 40 women with pregnancy-induced hypertension and 40 normotensive matched controls to determine if significant differences exist in dietary calcium intake and metabolic indices of calcium between these two groups. From 4-6 weeks postpartum, blood pressure, calcium intake, and the same biochemical markers will be reassessed in both lactating and non-lactating women. During years 2-5, we will prospectively assess blood pressure, nutrient intake, and markers of calcium metabolism in a group of 300 clinically normal women from 24 to 36 weeks of pregnancy. Nutrient intake, including dietary calcium, will be assessed during gestation weeks 24, 28, 32, 36, and the postpartum period using 3- day food records and 24-hour dietary recalls. Concomitantly, serum measures of calcium metabolism will be assessed including serum total and ionized calcium, parathyroid hormone, calcitonin, and 1,25(OH)2 vitamin D3 concentrations and serum magnesium, phosphorus, sodium, and potassium concentrations. During weeks 24 and 32, urinary excretion of sodium, calcium, magnesium, potassium, phosphorus, cAMP, and creatinine will be measured. Blood pressure will be measured at every prenatal visit and postpartum. Measures of infant growth and blood pressure will be assessed at 1, 6, and 12 months of age to determine if maternal dietary calcium intake, calcium metabolism, and/or maternal gestational blood pressure exert long-term influences on infant development and blood pressure. The results of this study will provide further insights into the possible role of dietary calcium intake and maternal calcium homeostasis in the regulation of blood pressure in normal pregnancy and pregnancy complicated by hypertension. These observations should provide data to construct testable hypotheses for further research into the putative mechanisms of calcium's influence in pregnancy-induced hypertension.
