Background: Pregnancy-induced hypertension is one of the major causes of both maternal and fetal death. Calcium can be prescribed to prevent the development of pre-eclampsia among the population with low calcium intake. However, there are only a few research studies on the effect of calcium alone, the impact of calcium co-administrated with other medications, and the timing of prescription during pregnancy.

Materials and Methods: The authors conducted a randomized, single-blind, controlled trial to evaluate the efficacy of high-dose calcium carbonate (CaCO_₃) co-administrate with aspirin in women with moderate to high risk of developing pre-eclampsia in reducing the incidence of pre-eclampsia. All pregnant women at 12 to 28 weeks of gestation having a moderate to high risk of developing pre-eclampsia were randomly assigned to receive aspirin with CaCO_₃ (3,750 mg/day), or aspirin with standard dose calcium carbonate (1,250 mg/day) until delivery or developed pre-eclampsia.

Results: One hundred thirty women underwent randomization with 64 women in the CaCO_₃ group and 66 women in the standard dose group. The incidence of pre-eclampsia was six cases in the high-dose group and eight cases in the controlled group (OR 0.8, 95% CI 0.3 to 2.6). The percentage of participants having adverse events related to high-dose and standard dose calcium carbonate did not differ significantly between the groups.

Conclusion: The use of CaCO_₃ at 3,750 mg/day, co-administrate with low-dose aspirin of 81 mg/day, starting at 12 to 28 weeks of gestation, resulted in a non-significantly difference in the incidence of pre-eclampsia with severe features.