Diagnosis and management of mirror syndrome: a case series with emphasis on the potential role of the sFLT-1/PlGF ratio in clinical practice

Objective: To characterize the maternal clinical, ultrasound, and laboratory parameters, maternal and perinatal outcomes of mirror syndrome, and to discuss the role of sFlt-1/PlGF biomarkers in diagnosis and management. Methods: We conducted a case series including all cases of mirror syndrome diagnosed at a tertiary reference center in Brazil. Clinical, laboratory, ultrasound, and biomarker data were collected, along with maternal and perinatal outcomes. Results: Nine cases of mirror syndrome were identified, with a mean gestational age at diagnosis of 27+6 weeks. The most frequent maternal findings were lower limb edema (n=7), hypertension (n=8), and proteinuria (n=8). Ultrasound demonstrated fetal hydrops (n=7), polyhydramnios (n=6), and placentomegaly (n=7). Laboratory abnormalities included abnormal proteinuria/creatinuria ratio in 5/8 women tested, elevated 24-hour proteinuria in all 5, anemia in 7, thrombocytopenia in 3, and elevated creatinine in 1. The sFlt-1/PlGF ratio was measured in 5 women; 4 had abnormal results, with 3 above 85, all of whom developed maternal complications or fetal death. Resolution occurred after a mean of 3.4±3.6 days, due to fetal death (n=3), delivery (n=5), or fetal surgery (n=1). In one monochorionic twin pregnancy complicated by twin-anemia-polycythemia sequence, biomarker normalization after intrauterine death of the hydropic twin allowed safe prolongation of the pregnancy and term delivery of the co-twin. Conclusion: Mirror syndrome should be suspected in pregnancies presenting with preeclampsia-like features in the setting of fetal hydrops or polyhydramnios. The sFlt-1/PlGF ratio may assist in differentiating mirror syndrome from preeclampsia and in identifying women at risk for adverse outcomes.