Perinatal outcomes of twin pregnancies affected by early twin-twin transfusion syndrome: a systematic review and meta-analysis.

INTRODUCTION: Twin-to-twin transfusion syndrome (TTTS) is associated with a high risk of perinatal mortality and morbidity if not treated. However, the optimal timing and management in case of early (occurring <18 weeks) TTTS has not been established yet. MATERIAL AND METHODS: This is a systematic review and meta-analysis aiming at evaluating the outcomes of monochorionic diamniotic (MCDA) twin pregnancies complicated by early (i.e. before 18 weeks) TTTS according to different management options (expectant, laser therapy, amnioreduction or cord occlusion). The primary outcome was mortality, including single and double intra-uterine, neonatal and perinatal death. Secondary outcomes were: composite morbidity, neuromorbidity, respiratory distress syndrome, admission to neonatal intensive care unit, intact survival (defined as survival free from neurological complications) and preterm birth <32 weeks' gestation. All outcomes were reviewed according to the different management options (expectant, laser therapy, amnioreduction or cord occlusion) and reported in the overall population of twins, and in the donor and recipient separately. Sub-group analysis for TTTS occurring before 16 weeks of gestation was performed. Random-effect meta-analyses of proportions were used to analyze the data. RESULTS: Thirteen studies were included. Early TTTS occurred in 14.3% (95% CI 11.9-17.0) of cases. Mortality: The incidence of intra-uterine death was 19.0% (95% CI 2.6-45.5) in twins managed expectantly, 32.4% (95% CI 16.5-50.7) in those who received laser treatment and 12.5% (95% CI 4.8-23.0) in those treated with amnioreduction. The incidence of neonatal death was 22.6% (95% CI 4.2-49.8) in twins managed expectantly, 24.7% (95% CI 0.5-80.3) in those who received laser and 20.2 (95% CI 5.8-43.4) in those who had amnioreduction, while it was not possible to compute the incidence of these outcomes in twins undergoing cord occlusion because of insufficient sample and lack of reporting of most of the observed outcomes. Overall, the incidence of perinatal death was 43.9% (95% CI 5.9-87.7) in twins managed expectantly, 47.3% (95% CI 21.4-70.) in those treated with laser and 28.5% in those who had amnioreduction. CONCLUSIONS: Twin pregnancies affected by early TTTS are at substantial risk of perinatal mortality and morbidity; however data comes from very small studies with high risk of selection bias.