Clinical characteristics of mirror syndrome: a retrospective study of 16 cases.

The exact prevalence of mirror syndrome remains unclear, and the precise clinical features need to be disclosed. We retrospectively reviewed 85 cases of foetal hydrops from a total of 98,484 deliveries. Of these 16 showed mirror syndrome, while 69 did not. The incidence of mirror syndrome among all deliveries was 0.0162%, while that among patients with foetal hydrops was 23.2%. Maternal symptoms of mirror syndrome included anaemia (n = 15), hypertension (n = 7), proteinuria (n = 8), pulmonary oedema (n = 3), cardiac failure (n = 2) and HELLP syndrome (n = 2). Placental thickness, placental weight and amniotic fluid index were significantly different between the groups. In the mirror syndrome group, uric acid, lactate dehydrogenase, creatinine and D-dimer levels were significantly higher (p < .05), whereas haemoglobin, serum albumin levels, haematocrit value and platelet count were significantly lower (p < .05). Elevated uric acid, lactate dehydrogenase and D-dimer levels may be useful as predictors of mirror syndrome.Impact statementWhat is already known on this subject? As mirror syndrome is uncommon and under-diagnosed, its exact incidence is not yet clear, and most publications are case reports or reviews of case reports.What the results of this study add? The incidence of mirror syndrome among all deliveries was 0.0162%, while that among patients with foetal hydrops was 23.2%. Pregnant women who develop mirror syndrome may show severe complications of pregnancy. Attention should be paid to the further progress of the condition. Placental thickness, placental weight and amniotic fluid index were significantly different between those with mirror syndrome and those without. In the mirror syndrome group, the uric acid, lactate dehydrogenase, creatinine and D-dimer levels were significantly higher (p < .05), whereas haemoglobin level, haematocrit value, platelet count and serum albumin level were significantly lower (p < .05).What the implications are of these findings for clinical practice and/or further research? Mirror syndrome is not rare among patients with foetal hydrops. Elevated uric acid, lactate dehydrogenase and D-dimer levels may be useful as predictors of mirror syndrome.