Abstract
BACKGROUND: Preeclampsia (PE) is a significant cause of maternal mortality worldwide, affecting 2% to 8% of pregnancies. The World Health Organization recommends the use of low-dose acetylsalicylic acid (100 mg of aspirin) and 1.5 to 2 g of calcium carbonate during pregnancy to prevent PE. However, robust evidence supporting the efficacy of calcium supplementation is still needed. This study aims to assess the efficacy of calcium carbonate in preventing preeclampsia in high-risk pregnant women. METHODS: A triple-blind, randomized clinical trial will be conducted at an outpatient clinic in Brazil between May 2024 and March 2026. Pregnant women at high risk of developing preeclampsia and with low dietary calcium intake will be randomly assigned to one of three groups: one group will receive calcium carbonate capsules (commercially available in Brazil) along with 100 mg of aspirin; the second group will receive calcium carbonate derived from Crassostrea sp. along with 100 mg of aspirin; and the control group will receive a placebo alongside 100 mg of aspirin. The primary outcome is the diagnosis of preeclampsia during pregnancy, while secondary outcomes evaluate maternal and fetal health indicators. DISCUSSION: This trial seeks to generate evidence on the efficacy of calcium carbonate in preeclampsia prevention, with a focus on comparing industrial calcium carbonate with calcium carbonate sourced from Crassostrea sp., a more sustainable alternative. TRIAL REGISTRATION: The study was approved by the Research Ethics Committee of the Federal University of Sergipe and registered in the Brazilian Registry of Clinical Trials (ReBEC), under the ID RBR-7hqhj3y. Registered on November 16, 2023.