Prenatal management and outcomes in mirror syndrome: report of two cases

Mirror syndrome (MS) is a rare obstetric complication characterized by fetal hydrops, placental edema, and maternal edema accompanied by the triad of hemodilution. MS is often misdiagnosed as preeclampsia, and its management must target the underlying fetal etiology. Currently, there remains a lack of systematic comparative studies addressing MS caused by different etiologies—particularly fetal-maternal transfusion (FMH) in twin pregnancies. This article reports two cases of MS occurring in primiparous women. Case 1: A 36-year-old woman at 25⁺⁹ weeks of gestation presented with dyspnea and edema. Ultrasound examination revealed a giant placental chorionic vascular malformation (7.2 × 6.5 × 5.8 cm), accompanied by fetal edema and placental edema. Laboratory tests indicated hemodilution (hemoglobin: 94 g/L; albumin: 22.7 g/L) and elevated liver enzymes. Given the inability to perform intrauterine treatment, the pregnancy was terminated following uterine artery embolization. Case 2: A 31-year-old woman with twin pregnancy at 29⁺⁹ weeks of gestation presented with progressive abdominal distension and dyspnea. Fetal edema was observed in both fetuses. Maternal alpha-fetoprotein (AFP: 4864.5 µg/L) and fetal hemoglobin (HbF: 4.3%) levels were significantly elevated, confirming fetal-maternal hemorrhage (FMH) as the precipitating factor. An emergency cesarean section was performed; both newborns (birth weights: 1450 g and 1440 g, respectively) survived after neonatal intensive care unit (NICU) management. Placental pathological examinations in both cases confirmed chorionic vascular malformation. Postpartum maternal symptoms resolved rapidly in both patients. The early identification of MS relies on distinguishing it from preeclampsia through its characteristic presentation of blood dilution rather than blood concentration. The management strategy depends on the underlying fetal etiology: when intrauterine treatment is feasible, targeted intervention may reverse both fetal and maternal clinical manifestations; otherwise, termination of pregnancy remains the definitive management approach. This comparative analysis of two distinct etiologies—massive chorangioma and FMH in twin pregnancies—emphasizes the importance of systematic diagnostic reasoning and individualized, multidisciplinary management.