First-trimester cord entanglement in monoamniotic twins

Objective Monoamniotic twinning occurs in only 1% of twin pregnancies, but carries a high perinatal mortality rate. Early and reliable diagnosis is es sential if attempts are to be made to reduce the complication rate. We repo rt color Doppler demonstration of cord entanglement in the first trimester, which is diagnostic of monoamnionicity. Methods Two patients with twin pregnancies were examined in the first trime ster with pulsed and color Doppler insonation of their umbilical arteries. Results Cord entanglement was suspected and proved by demonstrating differi ng fetal heart rate patterns in the same direction on umbilical artery Dopp ler analysis of a common mass of cord vessels. Following appropriate counse lling, medical amnioreduction was induced at 20 weeks of gestation to reduc e fetal movements and worsening cord entanglement. Delivery was by elective Cesarean section at 32 weeks' gestation and monoamnionicity was confirmed. Conclusion We report a new sign for the demonstration of monoamnionicity in twin pregnancies in the first trimester. This should improve the reliabili ty of early diagnosis, but further studies ave required to confirm that, if cord entanglement occurs, it is usually present by the end of the first tr imester.