Changes in Serum Calcium, Inorganic Phosphate and Phosphatase Activity in the Pregnant Woman

Abstract

That the serum calcium tends to diminish during pregnancy, especially in the later months, seems to be decisively established, notwithstanding a number of reports which are in conflict with this observation. The largest series of analyses are those of Mull and Bill who performed nearly 5000 determinations on a group of 900 subjects. Mull's results show an average fall of approximately 5 per cent. The decline is progressive as pregnancy advances, but is interrupted six to seven weeks before delivery; then there is a slight rise until delivery, followed by a sharper elevation after delivery. In a group of non-pregnant women studied by Oberst and Plass the average serum calcium was found to be 10.4 mgm. per 100 cc, which compares with the average of 10.6 mgm. reported by Mull and Bill, who also found that 94 per cent of their values fell between 10.0 and 11.5 mgm. Oberst and Plass saw no change early in pregnancy (variations between 9.8 and 10.9 mgm; average 10.4 mgm.), but during the eighth and ninth months the concentrations varied between 8.8 and 10.8 mgm., the average being 9.5 mgm. During labor the average was restored to