OBJECTIVES: To assess the natural history and perinatal outcome in monochorionic diamniotic twin pregnancies with discordant amniotic fluid volume without signs of severe twin-twin transfusion syndrome (TTTS). METHODS: This was an observational study of 84 consecutive monochorionic twin pregnancies which did not meet the criteria for severe TTTS and endoscopic laser coagulation of placental anastomoses at initial presentation. The population was subdivided into two groups. Group 1 consisted of 64 pregnancies (median gestational age, 20.1 (range, 15.6-24.7) weeks) with amniotic fluid discordance and no signs of congestive heart failure in the twin with the larger amniotic fluid volume (Twin 1) and positive end-diastolic flow in the umbilical artery of the twin with the smaller amniotic fluid volume (Twin 2). Group 2 (median gestational age, 19.1 (range, 16.0-24.4) weeks) consisted of 20 pregnancies with amniotic fluid discordance and intrauterine growth restriction (IUGR) (abdominal circumference <5th percentile) in combination with absent or reversed end-diastolic (ARED) flow in the umbilical artery of Twin 2. After exclusion of one patient from Group 1, who opted for termination of pregnancy, nine patients in Group 1 and one in Group 2 developed severe TTTS, and laser coagulation was offered. The remaining 54 pregnancies of Group 1 were compared with the remaining 19 pregnancies of Group 2. RESULTS: Fetuses in Group 1 showed significantly higher survival rates (overall survival, 100/108 (92.6%) vs. 23/38 (60%), P <0.0001; survival of both fetuses, 49/54 (90.7%) vs. 9/19 (47.4%), P = 0.0002) and median gestational age at delivery (33.6, (range, 27.6-37.8) weeks vs. 32.0 (range, 26.9-36.3) weeks, P = 0.0457). Overall, there was a significantly higher incidence of complications, defined as necessity for intrauterine intervention, fetal or neonatal death or delivery prior to 32 weeks, in Group 2 (Group 1: 30/63 (47.6%); Group 2: 16/20 (80%), P = 0.0188). CONCLUSIONS: Our data suggest that amniotic fluid discordance in monochorionic diamniotic twin pregnancies in combination with IUGR and umbilical artery ARED flow in one fetus represents an extremely high-risk constellation for adverse pregnancy outcome.
