Twin-to-twin transfusion syndrome

Twin-to twin transfusion syndrome (TTTS) may occur only in twins who shared placenta (monochorionic twins) since they are connected by some the blood vessels in the placenta they shared. It is normal for monochorionic twins to exchange some blood during gestation and this exchange is usually balanced, means that at one moment the 1st twin will act as the blood donor while the 2nd is the recipient, and at the next moment the 2nd twin will act as the donor while the 1st become recipient.

Twin-to twin transfusion syndrome (TTTS) occurs when the exchange is unbalanced, where one of the twins always donates blood to the other. Twin-to twin transfusion syndrome (TTTS) not only compromises the donor twin, but also the recipient twin. Because there is less blood goes to the donor and more blood goes to the recipient, the donor become volume depletion and the recipient become volume overload.

With lees volume, the donor unable to produce enough amniotic fluid thus develops oligohydramnios. He also doesn’t get enough nutrients to grow and shows signs of intrauterine growth restriction.

Meanwhile, the recipient, who receives excessive volume, will develop polyhydramnios due to the excessive fluid. The recipient also tends to swell and develop heart failure (hydrops), due to the volume overload.

The risk and severity of the condition vary, depends on when is the onset occurs. If it starts later in gestation, the risks are usually minimal, and if there is complication occurs there is an option to deliver the baby earlier when they are mature enough to survive outside the womb. However, if the condition occurs earlier, before the babies mature enough to survive outside the womb, then there are not many options left and the risk is greater. 

Twin – donor	Twin – recipient
Hypovolemia	Hypervolemia
Oliguria / anuria	Polyuria
Oligohydramnios	Polyhydramnios
May develops hydrops due to anemia and high-output heart failure	May develops hydrops due to hypervolemia
Hypotension	Hypertension, hypertrophic cardiomegaly, disseminated intravascular coagulation