Mirror syndrome: a systematic literature review

OBJECTIVE To review the diagnostic criteria for mirror syndrome and describe its clinical presentation. DATA SOURCES Databases from PubMed, Scopus, Cochrane Library, ClinicalTrials.gov, and CINAHL were queried for case series containing ≥ 2 cases of mirror syndrome from inception through February 2022. STUDY ELIGIBILITY CRITERIA Studies were included if they reported ≥ 2 cases of mirror syndrome and included case reports, case series, cohort studies, and case-control studies. STUDY APPRAISAL AND SYNTHESIS METHODS Studies' quality and risk of bias were independently assessed. Data were tabulated using Microsoft Excel and summarized using narrative review and descriptive statistics. This systematic review was performed according to the Preferred Reporting Item for Systematic Reviews and Meta-Analyses (PRISMA) statement. All eligible references were assessed. Screening of records and data extraction were independently performed, and a third author resolved disagreements. RESULTS Out of thirteen citations, twelve studies (n=82) reported diagnostic criteria for mirror syndrome: maternal edema (11/12), fetal hydrops (9/12), placental edema (6/12), placentomegaly (5/12), and preeclampsia (2/12). Twelve studies (n=82) described the clinical presentation of mirror syndrome as maternal edema (62.2%), hypoalbuminemia (54.9%), anemia (39.0%), and new onset hypertension (39.0%). Four studies (n=36) reported that hemodilution was present in all patients. Eight studies (n=36) reported the etiology of fetal hydrops, with the most common being structural cardiac malformations (19.4%), alpha thalassemia (19.4%), Rh isoimmunization (13.9%), and nonimmune hydrops fetalis (13.9%). Six studies (n=47) reported maternal complications, 89.4% of which were major: postpartum hemorrhage (44.7%), hemorrhage requiring blood transfusion (19.1%), ICU admission (12.8%), heart failure (10.6%), pulmonary edema (8.5%), and renal dysfunction (8.5%). In 39 cases, the reported fetal outcomes were stillbirth (66.6%) and neonatal or infant death (25.6%). The overall survival rate among continued pregnancies was 7.7%. CONCLUSION The diagnostic criteria of mirror syndrome differ considerably among studies. Mirror syndrome clinical presentation overlaps with preeclampsia. Only four studies discussed hemodilution. Significant maternal morbidity and fetal mortality were associated with mirror syndrome. Further research is warranted to elucidate the pathogenesis of mirror syndrome to better guide clinicians in identifying and managing the condition.