Which statement about monoamniotic twinning is true?

• A. Monoamniotic twins are associated with twin-to-twin transfusion.
• B. Monochorionic twins have an increased risk of umbilical cord entanglement.
• C. Monoamniotic twins are born with separate amniotic sacs.
• D. Monoamniotic twins have a shared amniotic sac and are at risk for umbilical cord entanglement.

Answer: (D)

Monoamniotic twinning means the twins share one amniotic sac. Because there’s a single sac, the two umbilical cords can move and twist around each other, making cord entanglement a real and serious risk. This sharing occurs in a monochorionic setting as well, so these pregnancies require close fetal monitoring and delivery earlier in pregnancy, often around 32–34 weeks, to prevent fetal compromise. That combination of a shared amniotic sac and the high risk of cord entanglement is the defining feature here. In contrast, having separate amniotic sacs would indicate diamniotic twinning, and while monochorionic placentation can lead to issues like twin-to-twin transfusion, cord entanglement is particularly characteristic of monoamniotic pregnancies.