Topic summary
Chorionic
Extracted from the Wikipedia article Chorion.
Monochorionic twins
Monochorionic twins are twins that share the same placenta. This occurs in 0.3% of all multiple-birth human pregnancies, and in 75% of monozygotic (identical) twins, when the split takes place on or after the third day after fertilization. The remaining 25% of monozygous twins become dichorionic diamniotic. The condition may affect any type of multiple birth, resulting in monochorionic multiples.