Placenta and membranes in twin pregnancies

(A) Two placentas, 2 amnions, 2 chorions (from either dizygotic twins or monozygotic twins with cleavage of zygote during first 3 days after fertilization).
(B) One placenta, 1 chorion, 2 amnions (monozygotic twins with cleavage of zygote from the 4^th to the 8^th day after fertilization).
(C) One placenta, 1 chorion, 1 amnion (monozygotic twins with cleavage of zygote from the 8^th to the 12^th day after fertilization).