Calcium metabolism in normal human pregnancy

Fifteen normal pregnant women and 9 female controls of similar age underwent mineral balance and calcium kinetic studies during and after pregnancy. 48Ca, a stable isotope, was employed in the pregnant women and specimens were measured by neutron activation analysis. Results were related to stage of pregnancy and demonstrated the expected and well documented retention of nitrogen, phosphorus, and calcium associated with fetal development. In addition, there was a 20% increase in miscible calcium pool by term, and an approximate doubling of both pool turnover and bone mineral accretion rates, both rising progressively with duration of pregnancy. Intestinal calcium absorption was twice usual normal levels from the earliest period studied and remained high throughout pregnancy. Virtually all these changes reverted to normal non-pregnant levels by 3 months after delivery. The importance of maternal adjustments as a component in these changes was emphasized by the presence of significant changes in ac...