Magnesium Sulfate as a Core Tocolytic in Open Fetal Myelomeningocele Repair: Maternal and Fetal Outcomes—A Narrative Review of Evidence from the MOMS Trial Era to 2024

Background/Objectives: Open fetal repair of myelomeningocele (MMC) requires profound and sustained uterine relaxation to permit hysterotomy and to prevent preterm labor after closure. Magnesium sulfate (MgSO4) has become the cornerstone postoperative tocolytic across North American fetal therapy centers, combined with volatile anesthetic-induced intraoperative tocolysis, indomethacin, and/or nifedipine. We synthesize the evidence on the mechanism, dosing, maternal safety, fetal/neonatal effects, and comparative performance of MgSO4 as the core tocolytic in open fetal MMC repair.