Single intrauterine fetal death in monochorionic diamniotic twin pregnancies complicated by twin anemia polycythemia sequence leads to significant risks for the surviving co-twin

INTRODUCTION: Most of the studies reporting the outcome of the surviving twin after single intra-uterine fetal death (sIUFD) focused on uncomplicated pregnancies or those affected by twin-to-twin transfusion syndrome, while there is a paucity of data for those complicated by twin anemia polycythemia sequence (TAPS). The aim of this systematic review was to report perinatal outcomes in monochorionic diamniotic (MCDA) twin pregnancies complicated by TAPS after sIUFD, according to gestational age at fetal loss and the presence of pregnancy-related comorbidities. MATERIAL AND METHODS: MEDLINE, EMBASE, and The Cochrane Library were searched for studies reporting the outcome of monochorionic twin pregnancies complicated by TAPS experiencing single IUFD. The primary outcome was the occurrence of co-twin IUFD. Secondary outcomes were neonatal death (NND), preterm birth (PTB) <34, <32, and <28 weeks of gestation, cerebral abnormalities detected at follow-up prenatal ultrasound, fetal magnetic resonance imaging (MRI) or postnatal imaging (ultrasound or MRI), and adverse neurodevelopmental outcome. Random-effects meta-analysis of proportions was used to analyze the data, and results were reported as pooled proportions or odd ratios (OR) with 95% CI. RESULTS: Eleven studies (83 twin pregnancies affected by TAPS, either spontaneous or post-laser, and complicated by single IUFD) were included in the systematic review and 10 (78 pregnancies) in the meta-analysis. Co-twin IUFD occurred in 4.9% (95% CI 1.1-11.3) after a single IUFD in pregnancies affected by TAPS, while there was no case of NND. PTB, either spontaneous or iatrogenic, occurred in 80.4% (95% CI 44.3-99.5) <34 weeks, and 50.0% (95% CI 16.3-83.7) <28 weeks of cases. Intra-uterine transfusion was required in 8.0% (95% CI 0.9-38.3). Cerebral anomalies at follow-up ultrasound or fetal MRI were reported in 15.0% (95% CI 8.2-78.3) and 11.4% (95% CI 2.4-55.7) of cases, while anomalies at post-natal imaging in 9.4% (95% CI 5.6-57.6) of cases. It was not possible to perform a meaningful pooled data synthesis on the observed outcomes according to the type and staging of TAPS and according to the donor or recipient twin. CONCLUSIONS: The occurrence of co-twin death after single IUFD in pregnancies complicated by TAPS appears low, while cerebral abnormalities detected either pre- or post-natally occur in 10-15% of cases. Further evidence is needed to elucidate the long-term neurological and neurodevelopmental risk of these children.