TTTS occurs in monochorionic, monozygotic twins. The donor twin is often smaller and anemic at birth. The recipient twin is usually larger and plethoric at birth.2. Also known as Feto-Fetal Transfusion Syndrome (FFTS) and Twin Oligohydramnios-Polyhydramnios Sequence (TOPS) is a complication with high morbidity and mortality that can affect identical twins or higher multiple pregnancies where two or more fetuses share a common (monochorionic) placenta.
In twin-to-twin transfusion syndrome, the twins share not only the same placenta but some of the same blood circulation; in other words, they essentially share a single blood supply. This allows the transfusion of blood from one twin (the donor) to the other (the recipient).
The donor twin becomes small and anemic, and the recipient twin becomes large and overloaded with blood.
The transfusion causes the donor twin to have decreased blood volume, retarding the donor's development and growth, and also decreased urinary output, leading to a lower than normal level of amniotic fluid (becoming oligohydramnios).
The blood volume of the recipient is increased, which can strain the donor's heart and eventually lead to heart failure, and also higher than normal urinary output, which can lead to excess amniotic fluid (becoming polyhydramnios).