Twin-to-twin transfusion 2017-06-30T16:02:43Z Twin to twin transfusion syndrome As a result of sharing a single placenta, the blood supplies of monochorionic twin fetuses can become connected, so that they share blood circulation: although each fetus uses its own portion of the placenta, the connecting blood vessels within the placenta allow blood to pass from one twin to the other.Depending on the number, type and direction of the interconnecting blood vessels (anastomoses), blood can be transferred disproportionately from one twin (the donor) to the other (the recipient). This state of transfusion causes the donor twin to have decreased blood volume, retarding the donor's development and growth. The blood volume of the recipient twin is increased, which can strain the fetus's heart and eventually lead to heart failure. Abnormal fetal physiology