Mirror syndrome in monochorionic diamniotic twins presenting as maternal hyponatremia: A case report

This is a case report of a 39-year-old patient, G5P1031, with monochorionic diamniotic twins at 30 weeks and 1 day of gestation, who developed mirror syndrome without twin-to-twin transfusion syndrome (TTTS) with a unique presentation of maternal and neonatal hyponatremia. Coinciding with severe hyponatremia were maternal symptoms of edema, nausea and vomiting, hypoalbuminemia, elevated uric acid, as well as fetal selective growth restriction, polyhydramnios, umbilical artery absent end diastolic flow and prolonged bradycardia of twin B. Given the poor status of twin B and the risks to twin A, the patient underwent emergent cesarean delivery. Hyponatremia in all three patients resolved in the following 48-72 h. Mirror syndrome is associated with significant maternal and fetal morbidity and mortality. In this case, severe hyponatremia posed additional risks. Therefore, electrolyte monitoring should be considered in both mother and neonate(s).