Background: Monoamniotic twin pregnancies are frequently associated with cord entanglement, but such entanglement rarely involves the co-twin's trunk, extremities, or neck.
Case: We report a set of monoamniotic twins in which color Doppler imaging revealed that the cord of twin B was wrapped around the neck of its dead co-twin. This knowledge allowed us to avoid clamping and dividing twin A's nuchal cord during vaginal delivery, preventing asphyxia of twin B. This is the fifth reported incidence of this particular monoamniotic complication and the first to be diagnosed prenatally.
Conclusion: Color Doppler imaging facilitates the diagnosis of rare cord complications in monoamniotic twin pregnancies.