Perinatal outcome in very preterm births with twin-twin transfusion syndrome.

We retrospectively studied 48 pairs of twin gestations delivered between 24 and 28 weeks' gestation from 1975 to 1986 at Vanderbilt University Medical Center. The incidence of fetofetal transfusion syndrome was 20%, more than double the incidence previously reported in large series of twin deliveries that encompassed a wider gestational age range. The overall mortality was 55%, and mortality for the fetofetal transfusion group was 70%, whereas a subset of the fetofetal transfusion group, those without weight discordancy, had a mortality rate of 75%. Our findings suggest that traditional reliance on ultrasonographic criteria for diagnosis of fetofetal transfusion will not detect 40% of such cases. The poor outcome data suggest a need for innovative approaches to diagnosis and treatment.