Twin-to-Twin Transfusion Syndrome

Being pregnant with twins can be a very joyful experience. After all, you get to nurture two babies, instead of just one! However, a twin pregnancy can also be quite a stressful, particularly when there is an increased chance of certain pregnancy complications. In particular, some twins develop a problem with their circulation, known as Twin-to-Twin Transfusion Syndrome. This syndrome is very dangerous and can inhibit the development of one twin while leading to a variety of health complications for both twins. When left untreated, Twin-to-Twin Transfusion Syndrome (TTTS) is often fatal.

What is Twin-to-Twin Transfusion Syndrome?
TTTS is a pregnancy complication that affects identical twins. Specifically, TTTS affects the placenta, preventing proper circulation of blood and nutrients between the two twins. This can lead to severe developmental deficits and health complications.

TTTS only affects twins that have a monochorionic placenta. This occurs when twins develop a shared placenta in the uterus, instead of two separate placentas. If a fertilized egg takes longer than four days to split, only one placenta develops instead of two. Typically, this placenta is able to balance nutrients and blood flow to both babies.

However, in 5% to 25% of twins with a monochorionic placenta, abnormal blood vessels form inside of the placenta. As a result, blood flow becomes imbalanced and one baby begins to act as a filter for the placental blood. Known as the donor twin, this twin pumps blood for both himself and his twin, causing excessive heart strain and poor development. Meanwhile, the recipient twin receives too much blood, and begins to develop too quickly, producing a large amniotic sac.

How Common is Twin-to-Twin Transfusion Syndrome?
It was once thought that TTTS was a very rare illness, affecting only a minute percentage of all twin pregnancies. New research on the subject, though, has shown that TTTS actually affects more pregnancies than previously thought. It appears that about 1 in 1000 identical twin births are affected by TTTS. Both male and female identical twins are affected at the same rate.

What Causes Twin-to-Twin Transfusion Syndrome?
The cause of TTTS remains elusive to researchers. It appears that anybody can develop TTTS, regardless of genetic background or medical history. Scientists believe that the position of the twins in the placenta may contribute to TTTS, particularly if one twin is taking up a greater percentage of the placenta than the other. However, the exact cause of the syndrome is still unknown.

Symptoms of Twin-To-Twin Transfusion Syndrome
TTTS can manifest at any time during pregnancy, from the first trimester right up until labor and delivery. It most commonly occurs during the fourth and fifth months of pregnancy. Both mother and babies will exhibit symptoms of TTTS. Symptoms in mom include:

rapid weight gain (due to excess amniotic fluid around the recipient twin)
abdominal pain and tightness
premature contractions

Symptoms in the twin babies include:

monochorionic placenta
one small baby and one large baby
one small amniotic sac and one large amniotic sac

Complications of Twin-to-Twin Transfusion Syndrome
Unfortunately, TTTS is a very dangerous illness that can drastically affect the health of your twins. Common complications of TTTS include:

heart failure in the donor twin (from pumping too much blood)
anemia in the donor twin
poor fetal development in the donor twin
excess amniotic fluid in the recipient twin, leading to premature rupture of the membranes
preterm labor
brain damage, heart damage, or fetal death

Treatment of Twin-to-Twin Transfusion Syndrome
Treatment is essential if you are suffering from TTTS. Without treatment, between 80% and 100% of babies die, either in utero or shortly after birth. Treatment can help to resolve circulation problems between the twins allowing for healthy fetal growth. Common treatment options include:

Amnioreduction: Amnioreduction is used to help remove some of the excess amniotic fluid from around the recipient twin. This can help to reduce your discomfort and the risk of preterm labor. Using a large needle, your health care provider can drain off some of the excess amniotic fluid. This procedure usually takes about an hour and removes anywhere between one and three liters of excess amniotic fluid. Afterwards, the donor twin has more room to grow and develop.

Septostomy: A septostomy is usually performed along with an amnioreduction. A hole is created in the amniotic membranes with a needle. Amniotic fluid is then allowed to re-balance itself, allowing each twin to have the same amount of amniotic fluid.

Laser Treatment: Laser treatment aims to destroy the abnormal blood vessels in the placenta that are responsible for the poor blood circulation between the two twins. A scope is passed through the abdomen and into the recipient twin’s amniotic sac. A laser is then passed through the scope and used to break the abnormal blood vessels. This laser treatment often helps to normalize blood flow and sometimes works to completely eliminate the TTTS.

Umbilical Cord Occlusion: Occasionally, TTTS causes one twin to become sick or to die in utero. In this case, the other twin may still receive the blood from the sick twin and, as a result, could also become sick. Umbilical cord occlusion uses a special instrument to tie off the umbilical cord of the sick baby. This will cause the sick baby to die, but will save the remaining twin.

Prognosis of Twin to Twin Transfusion Syndrome
Unfortunately, the prognosis of TTTS is not very good. If untreated, most twins die in utero or shortly after birth. Even with treatment, it is not always possible to save twins suffering from TTTS. Treatment generally increases survival rates by between 20% and 50%. However, many babies are born with physical or developmental disabilities even with treatment.

If you are having twins, it is important to receive proper prenatal care in order to ensure quick diagnosis of TTTS.