Monoamniotic twins

Monoamniotic twins are identical or semi-identical twins who share the same amniotic sac within the mother's uterus, and are always monochorionic, sharing one placenta but with two separate umbilical cords. The condition is rare, occurring in roughly one in 35,000 to 60,000 pregnancies. Its main risks are cord entanglement, which can hinder fetal movement and complicate delivery, cord compression by one twin against the other, which can restrict blood and nutrient flow and cause fetal death, and twin-to-twin transfusion syndrome, in which one twin receives disproportionate nourishment. Modern aggressive fetal monitoring, with continuous monitoring and planned premature delivery by cesarean section around 32 to 34 weeks, has raised survival rates to between 81 and 95 percent, up from earlier estimates of 50 to 60 percent.