Mirror syndrome is a rare and serious maternal condition associated with immune and non-immune fetal hydrops after 16 weeks of gestational age. Subjacent conditions associated with fetal hydrops may carry different risks for Mirror syndrome. Fetuses with Turner syndrome are frequently found to be hydropic on ultrasound. We designed a retrospective multicenter study to evaluate the risk for Mirror syndrome among pregnancies complicated with Turner syndrome and fetal hydrops. Data were extracted from a questionnaire sent to specialists in maternal fetal medicine in Germany. Out of 758 cases, 138 fulfilled our inclusion criteria and were included in the analysis. Of the included 138, 66 presented with persisting hydrops at or after 16 weeks. The frequency of placental hydrops/placentomegaly was rather low (8.1%). Of note, no Mirror syndrome was observed in our study cohort. We propose that the risk of this pregnancy complication varies according to the subjacent cause of fetal hydrops. In Turner syndrome, the risk for Mirror syndrome is lower than that reported in the literature. Our observations are relevant for clinical management and parental counseling.
Keywords: Mirror syndrome; Turner syndrome; fetal hydrops; monosomy X; placental hydrops; placentomegaly.