The prevalence and clinical features of twin-twin transfusion syndrome with onset during the third trimester.

OBJECTIVE To describe the incidence and clinical features of twin-twin transfusion syndrome (TTTS) with third trimester onset. METHODS We performed a retrospective chart review of monochorionic diamniotic (MD) twin pregnancies delivered during a recent 4-year period. The inclusion criterion was women who received prenatal care at our center from the first trimester onward. Serial ultrasound examinations were performed at least every 2 weeks until delivery to evaluate fetal growth as well as to estimate amniotic fluid volume. The prevalence of TTTS onset after 28 weeks of gestation and clinical features, including neonatal outcomes and placental findings, were elucidated. RESULTS Meeting our inclusion criterion were 143 MD twin pregnancies, including 15 TTTS cases (10%). Five cases (4%) developed TTTS during the third trimester and underwent a cesarean section immediately after the diagnosis. All of these women exhibited either abdominal distension or uterine contractions. Recipient twins tended to require more intensive cardiopulmonary treatment than donors, however, neither a recipient nor a donor twin suffered neonatal death or neurological impairment. Placental arterio-arterial anastomoses were detected in three out of five cases. Arteriovenous anastomoses were present in all cases, however, venovenous anastomoses were not found in any case. CONCLUSIONS TTTS is a relatively rare complication during the third trimester. It is imperative to be observant for the development of TTTS in MD twin pregnancies with any abdominal symptoms, even if they appear insignificant.