title: A randomized controlled trial of the effect of third-trimester calcium supplementation on maternal hemodynamic function.
abstract: OBJECTIVE
  To determine the effect of third-trimester calcium supplementation on maternal hemodynamic function.
  
  
  METHODS
  Pregnant women were randomized to receive either 1.5 g of elemental calcium or placebo for 6 weeks during the third trimester. Using Doppler technique, maternal hemodynamic characteristics were measured at baseline, at 2 hours after the first dose of study drug, and at the completion of 6 weeks. Serum, dietary, and urinary calcium levels were also assessed. Power calculation indicated the need to study ten subjects in each group to detect a 1.2 L (20%) difference in cardiac output between groups, assuming a mean of 6.2 +/- 1.0 L/minute. Data were analyzed by analysis of variance for repeated measures, Student t test, Mann-Whitney U test, and Fisher exact test.
  
  
  RESULTS
  Twenty-three women enrolled, and 18 completed the study. There were no statistically significant differences in demographic characteristics or in serum, dietary, or urinary calcium levels between the two groups. There were also no statistically significant differences in hemodynamic function over time within the calcium supplementation or placebo group (P > .05; analysis of variance for repeated measures). After 6 weeks, there were no significant differences between the calcium- and placebo-treated subjects in any hemodynamic measurement. Specifically, there was not a statistically significant difference in cardiac output (7.3 +/- 1.2 L/minute versus 8.0 +/- 0.9 L/minute; P = .09) between the calcium- and placebo-treated groups.
  
  
  CONCLUSIONS
  These findings suggest that third-trimester calcium supplementation does not significantly alter cardiac output. The mechanism by which calcium supplementation lowers blood pressure remains to be elucidated.
authors.affiliation: Department of Obstetrics and Gynecology, University of Washington Medical Center, Seattle, USA. bogge001@mc.duke.edu
authors.forename: K A
authors.initials: KA
authors.lastname: Boggess
authors.forename: L
authors.initials: L
authors.lastname: Samuel
authors.forename: B C
authors.initials: BC
authors.lastname: Schmucker
authors.forename: J
authors.initials: J
authors.lastname: Waters
authors.forename: T R
authors.initials: TR
authors.lastname: Easterling
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D002118:Calcium / Q000378:metabolism; D002119:Calcium Carbonate / Q000627:therapeutic use*; D002136:Calcium, Dietary / Q000008:administration & dosage; D002302:Cardiac Output / Q000187:drug effects*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D011247:Pregnancy / Q000187:drug effects / Q000502:physiology*; D011263:Pregnancy Trimester, Third; D013997:Time Factors
chemical_list: D002136:Calcium, Dietary; D002119:Calcium Carbonate; D002118:Calcium