Objective: To assess the outcome of a geographically based cohort of monochorionic twin pregnancies complicated by twin-twin transfusion syndrome managed in a single perinatal center over a 10-year period.
Methods: A prospective cohort design was established in 1992 within a single tertiary obstetric unit.
Results: Sixty-nine cases of twin-twin transfusion syndrome were identified during the study period. The median gestation at diagnosis was 22.1 weeks (interquartile range 19.7-25.4). Perinatal outcome was directly related to stage at diagnosis and gestation at delivery. The overall perinatal survival rate was 64.5%. For lesser disease severity (stages I and II) the perinatal survival rate was 76.4%, falling to 51.5% with increasing disease severity (stages III-V) (P =.004). The median gestation at delivery was 29.4 weeks (interquartile range 26.3-33.8). The perinatal survival for those born at less than 28 weeks' gestation was 27.1%, increasing to 84.4% for those born at more than 28 weeks' gestation (P =.001). The incidence of neonatal complications reflected the high preterm birth rate. Amnioreduction was the principal intervention employed in this series, but in 24.6% of cases no therapy was used because of the requirement for immediate delivery or fetal demise.
Conclusion: Twin-twin transfusion syndrome is a heterogeneous disorder in its clinical manifestations and progress. There remain significant perinatal mortality and morbidity in pregnancies complicated by twin-twin transfusion syndrome, principally related to the high preterm birth rate that typifies this disorder. The severity of disease as assessed by stage and the gestation at delivery are the principal factors in determining perinatal outcome in this condition.