A comparison of maternal calcium and magnesium levels in pre-eclamptic and normotensive pregnancies: An observational case-control study

Objective: Supplementing pregnant women at high risk of developing pre-eclampsia with calcium may reduce the incidence of the disease. This study examines differences in serum and hair concentrations of calcium and magnesium between women with pre-eclamptic and normotensive pregnancies. Design: Observational case-control study. Setting: Two teaching hospitals in Cape Town, South Africa. Population: Women with pre-eclamptic (N = 96) or normotensive (N = 96) pregnancies, who delivered a single, live infant. Methods: Demographic and current pregnancy details were retrieved from clinical notes. Each participant completed a dietary questionnaire. Venous blood samples were taken from each participant to assess serum calcium and magnesium concentrations. Hair samples were obtained from all participants and calcium and magnesium levels were measured by inductively coupled plasma optical emission spectrometry (ICPOES). Main outcome measure: Hair and serum calcium and magnesium concentrations were compared between women with pre-eclamptic and normotensive pregnancies. Results: Diet and socio-economic status in the two groups were similar. There was no significant difference in the hair calcium level between women with pre-eclamptic [1241 parts per million (ppm); range, 331-4654 ppm] and normotensive (1146 ppm; range, 480-4136 ppm) pregnancies (P = 0.5). Hair calcium levels in both groups were not affected by HIV infection. Conclusion: Woman with pre-eclampsia showed no difference in chronic calcium status relative to normotensive women. This finding does not support the current belief that the mechanism by which calcium supplementation reduces the risk of developing pre-eclampsia is by correcting a nutritional deficiency. © 2013 Royal College of Obstetricians and Gynaecologists.