CALCIUM INTAKE, METABOLISM &GESTATIONAL BLOOD PRESSURE

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.