Clinical presentation and maternal-fetal outcomes of Mirror Syndrome: A case series of 10 affected pregnancies

Background: Mirror Syndrome, also known as Ballantyne syndrome, is a rare condition with fewer than 120 cases described in the literature. A simultaneous edematous state of the mother, fetus and placenta is pathognomonic, with the maternal condition frequently presenting with signs and symptoms similar to that of preeclampsia. Objective: Our aim was to add to the international body of literature through identification of all cases of Mirror Syndrome at two Canadian tertiary obstetric centres and characterize the maternal presentation, laboratory findings, and perinatal outcomes. Methodology: We performed a retrospective chart review of all cases of fetal hydrops from two tertiary centres in Winnipeg (Manitoba, Canada) between 2000 and 2019. There were 276 cases of fetal hydrops during this period, of which 10 cases satisfied the diagnostic criteria for Mirror Syndrome where maternal and perinatal outcomes were analysed. Results: The median gestational age at diagnosis with Mirror Syndrome was 23 weeks and 3 days of gestation and at birth was 25 weeks and 0 days of gestation. The majority of women were multiparous (80%) and had elevated maternal body mass index (median 33 kg/m²). The most common maternal clinical findings included weight gain (100%) and hypertension (90%). The most common laboratory findings included low hematocrit (100%), hypoalbuminemia (80%), anemia (70%) and hyperuricemia (70%). Structural anomalies were observed in 50% of cases, over half of the fetuses were stillborn (66.7%) and one quarter of pregnancies resulted in neonatal deaths (25%). The median time until maternal improvement of Mirror Syndrome was 2 days postpartum. Conclusion: Mirror Syndrome affected 3.6% of all cases of fetal hydrops in our cohort, and showed associations with multiparity, elevated BMI, hemodilution, hypoalbuminemia, anemia and hyperuricemia. Delivery is frequently required for fetal and/or maternal indications and symptoms usually improved rapidly after delivery.