Monochorionic-Diamniotic Twins

Monochorionic-diamniotic (MCDA) twins are twins that share a placenta but have their own amniotic sac. They are almost always monozygotic, meaning that they come from one egg that is fertilized by one sperm, and therefore are identical.

Monochorionic-diamniotic twins occur in 0.3% of all pregnancies and 70 to 75% of all monozygotic twin pregnancies and occur completely at random.