Figure 7. This diagram shows schematically the random variations in placental sharing and blood flow through the blood vessel connections in MC twin placentas. Twin babies with asymmetrically small placentas could benefit if they are recipients of blood transfusions from the twin with the larger placenta. Conversely, twins with small shares will be further compromised if they are the donors in TTTS. Depending on the degree of asymmetry (bottom row), placental insufficiency may express itself in the twin with a small share at different gestational ages. Arrows = direction and degree of blood flow; hatch marks = location of vascular equator; small open and closed circles = umbilical cord insertion sites. (Diagram courtesy of Dr. Julian E. De Lia)