Twin to twin transfusion syndrome (TTTS) is a disease of the placenta that affects identical twin pregnancies. TTTS affects identical twins, triplets or more, who share a placenta.
The shared placenta contains abnormal blood vessels, which connect the umbilical cords and circulations of the twins.
The placenta may also be shared unequally by the twins, and one twin may have a share too small to provide the necessary nutrients to grow normally or even survive.
TTTS is not hereditary or genetic, nor is it caused by anything the parents did or did not do. TTTS can happen to anyone.
The transfusion causes the donor twin to have decreased blood volume. This in turn leads to slower than normal growth than the other twin and poor urinary output causing little to no amniotic fluid or oligohydramnios
The recipient twin becomes overloaded with blood. This excess blood puts a strain on this baby’s heart to the point that it may develop heart failure, and also causes this baby to have too much amniotic fluid (polyhydramnios) from a greater than normal production of urine.
The placenta is an amazing organ but if shared by twins in one outer membrane, can cause complications. Twins who have their own placenta and membranes- often known as DCDA (dichorionic diamniotic) are at far less risk of complications.