Objective: To evaluate the efficacy of oral supplemental calcium in reducing the incidence of pregnancy-induced hypertension (gestational hypertension or preeclampsia) in angiotensin-sensitive nulliparas.
Methods: Sensitivity to intravenously infused angiotensin was determined at 24-28 weeks' gestation in 281 nulliparous women who had positive roll-over tests. Angiotensin-sensitive women were given 2 g/day of oral elemental calcium or placebo in a randomized, double-blind clinical trial. The tablets were dispensed by the hospital pharmacy in serially numbered computerized pill bottles so as to assess compliance. Repeat angiotensin sensitivity test was performed at 34-36 weeks' gestation.
Results: Sixty-three of 67 angiotensin-sensitive nulliparas were evaluable; 29 received calcium and 34 received placebo tablets. Four of 29 calcium-treated subjects (13.8%, 95% confidence interval [CI] 4-32%) developed preeclampsia, compared to 15 of 34 (44.1%, 95% CI 27-62%) in the placebo group (relative risk [RR] 0.37, 95% CI 0.15-0.92; P = .01). The incidence of any type of hypertension was nine of 29 (31%, 95% CI 15-51%) with calcium treatment, compared to 22 of 34 (64.7%, 95% CI 46-80%) with placebo (RR 0.46, 95% CI 0.25-0.86; P = .01).
Conclusion: Calcium supplementation given in pregnancy to high-risk nulliparas reduces the incidence of pregnancy-induced hypertension.