A monochorionic pregnancy is a type of twin or multiple gestation in which the fetuses share a single placenta but are separated into either two separate amniotic sacs (diamniotic-monochorionic) or a shared amniotic sac (monoamniotic-monochorionic). Monochorionic pregnancies are more common in identical (monozygotic) twins but can rarely occur in dizygotic twins. On ultrasound, monochorionic gestation is confirmed by visualizing a single placental mass without a separate chorionic layer dividing the two fetuses. These pregnancies carry increased risk of complications such as twin-to-twin transfusion syndrome (TTTS) and selective intrauterine growth restriction. More frequent ultrasound surveillance is recommended to monitor for these complications.
Sonography Term