Methods: This is a study protocol of a randomized, controlled, phase 3, triple-blind, randomized clinical trial. The classification is based on the gestational age at the time of diagnosis of mild preeclampsia (early-onset or late-onset preeclampsia). Participants will be 128 pregnant women with mild pre-eclampsia (systolic blood pressure between 140-160 mm Hg or diastolic blood pressure between 90-110 mm Hg, along with other preeclampsia symptoms). Participants will divide into two intervention and control groups using a 1:1 random allocation ratio randomly. They will receive one oral capsule (the concentration of 109 CFU) or placebo daily from admission until delivery. Primary outcomes included mean systolic and diastolic blood pressure, mean gestational age from diagnosis to delivery, and mean birth weight. Also, secondary outcomes included proteinuria, serum creatinine level, the incidence of severe PE, the use of antihypertensive drugs, the rate of natural delivery, incidence of serious complications, maternal blood factors such as platelet count, and serum levels of liver enzymes such as ALT, AST, bilirubin, and LDH.

Discussion: The present trial can importantly contribute to the selection of an appropriate Synbiotic supplement as safe pharmaceutical adjuvants in the treatment of pregnant women with mild preeclampsia and prevention of maternal and neonatal complications.

Trial Registration: IRCT20110606006709N20. Registered on August 13, 2022.