Amniotic fluid pressure in twin-to-twin transfusion syndrome: an objective prognostic factor.

Severe twin-to-twin transfusion syndrome presenting before 28 weeks' gestation is associated with a high neonatal mortality and morbidity due to polyhydramnios-related very premature delivery or intrauterine death of one or both twins. Management options include serial amniodrainages or laser coagulation of the intertwin placental anastomoses; however, early antenatal prognostic factors are lacking. Serial amniocenteses were performed in 9 pregnancies with twin-to-twin transfusion syndrome presenting with second-trimester polyhydramnios, and serial measurements of amniotic fluid pressure were made. Although in 8 cases the pre-drainage pressure was above the 95th centile of the normal range for singleton pregnancies, the pressures were lower in the pregnancies resulting in two livebirths than in the cases where one or both babies died. This study suggests that patients presenting with intraamniotic pressure > 17 mm Hg cannot be safely managed by serial amniodrainages.