Mirror syndrome: a systematic literature review

Objective: This study aimed 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 inquired for case series containing ≥2 cases of mirror syndrome from inception to 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: The 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 conducted according to the Preferred Reporting Item for Systematic Reviews and Meta-Analyses statement. All eligible references were assessed. Screening of records and data extraction were independently performed, and a third author resolved disagreements.

Results: Of 13 citations, 12 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); 12 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%); 4 studies (n=36) reported that hemodilution was present in all patients; 8 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%); and 6 studies (n=47) reported maternal complications, 89.4% of which were major: postpartum hemorrhage (44.7%), hemorrhage requiring blood transfusion (19.1%), intensive care unit 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 differed considerably among studies. Mirror syndrome clinical presentation overlapped with preeclampsia. Only 4 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.