Background: Monoamniotic twinning is a rare event with a high perinatal mortality rate from cord accidents. To date, only a few cases have been reported in which cord entanglement was diagnosed with Doppler ultrasonography.
Case: In a monoamniotic twin pregnancy, umbilical cord entanglement was diagnosed at 20 weeks' gestation by color flow Doppler ultrasonography. The entanglement was associated with growth discordance between the twins and subsequent death of the smaller fetus.
Conclusion: The rarity of this condition hinders our understanding of the pathophysiology and development of management protocols.