Calcium supplementation during pregnancy for preventing hypertensive disorders is not associated with changes in platelet count, urate, and urinary protein: a randomized control trial.

Objective: To test the hypothesis that calcium supplementation inhibits the underlying pathological processes in women with preeclampsia.

Methods: Seven hundred and eight nulliparous women were enrolled in a WHO randomized double-blind trial, who received 1.5 g of calcium or placebo from 20 weeks of pregnancy or earlier. Platelet count, serum urate, and urinary protein/creatinine ratio were measured at or near 35 gestational weeks.

Results: No difference was detected in rates of abnormal platelet count (relative risk [RR] 1.18; 95% confidence interval [CI], 0.63 to 2.18), serum urate level (1.0; 0.64 to 1.57) or urine protein/creatinine ratio (1.01; 0.76 to 1.34). This was consistent with the main trial finding of no difference in the incidence of 'dipstick' proteinuria between women receiving calcium and those receiving placebo (8312 women; RR, 1.01; 95% CI, 0.88 to 1.15).

Conclusions: An effect of calcium supplementation in the second half of pregnancy on the rate of abnormal laboratory measures associated with preeclampsia was not demonstrated.