Natural history of twin-twin transfusion syndrome

To determine the natural history of pregnancies with twin-twin transfusion syndrome (TTTS).

All cases of TTTS at our institution since 1991 and in a MED-LINE search since 1966 were retrospectively reviewed. The prenatal diagnosis of TTTS required the presence of monochorionic/diamniotic placentation (absence of twin-peak sign, thin membrane, single placenta, same sex) and of polyhydramnios (largest pocket > 8 cm) in one sac and oligohydramnios (largest pocket < 2 cm or stuck twin) in the other. Only cases diagnosed at < or = 28 weeks were included. Upon diagnosis, all patients were counseled as to the availability, risks and benefits of serial amniocentesis, laser therapy, septostomy, umbilical cord ligation, and other medical and surgical interventions.

Of 29 pregnancies identified at our institution with the above strict criteria for TTTS, 5 (17%) declined in utero therapy and were managed expectantly. The mean gestational age at presentation was 19.2 weeks (range, 16-28) and at delivery, 33.8 weeks (range, 22-41). Four (40%) of the twins survived past the neonatal period, and of the three with follow-up, all are free of neurologic sequelae despite the death in utero of their cotwin. From the literature, 136 fetuses with TTTS as defined above and managed expectantly were identified; 37 (27%) survived; 75% (9/12) of survivors with follow-up are neurologically normal. The most recent four studies have reported survival of untreated cases of 50% (17/34) when diagnosed at < or = 26 weeks and of 63% (20/32) when diagnosed at < or = 28 weeks.

The perinatal survival of TTTS pregnancies managed without in utero procedures is approximately 30% overall and 63% in the four most recent series when diagnosed at < or = 28 weeks. The success of in utero therapeutic intervention should be assessed by randomized studies or at least compared to that in similar cases managed without such intervention.