What is Twin-to-Twin Transfusion Syndrome (TTTS)?

TTTS is a rare, but serious disease of the placenta (or afterbirth) that affects identical twin pregnancies (or higher multiple gestations) where a placenta is shared. TTTS is also referred to as Chronic Intertwin Transfusion Syndrome.

In TTTS, the common placenta contains abnormal blood vessels that are connected to the umbilical cord, affecting the blood circulation of the twins. Depending on the number, type and direction of the connecting vessels, blood can be transfused disproportionately from one twin (the donor) to the other twin (the recipient). The transfusion causes the donor twin to have decreased blood volume. This in turn leads to slower than normal growth than its co-twin, and poor urinary output causing little to no amniotic fluid or oligohydraminos (the source of most of the amniotic fluid is urine from the baby).

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 (polyhydraminos ) from a greater than normal production of urine.


There are no known causes of TTTS and it can happen to anyone pregnant identical twins (or higher gestations sharing the same amniotic sac). TTTS occurs in about 15 percent of identical twin pregnancies.

(Sources: The Twin to Twin Transfusion Syndrome FoundationUS National Library of Medicine)

Diagnosis
TTTS is usually diagnosed through an ultrasound during pregnancy before 28 weeks gestation.

Some TTTS symptoms that may be seen on an ultrasound include:

  • A significant difference in the size of fetuses of the same gender
  • Difference in size between the two amniotic sacs
  • Difference in size of the umbilical cords
  • A single placenta
  • Evidence of fluid build up in the skin of either fetus
  • Findings of congestive heart failure in the recipient twin
  • Polyhydraminos (excess amniotic fluid) in the recipient twin
  • Oligohydraminos (decreased or too little amniotic fluid) in the donor twin

A mother with TTTS may experience the following:

  • Sensation of rapid growth of the womb
  • A uterus that measures large for dates
  • Abdominal pain, tightness, or contractions
  • Sudden increase in body weight
  • Swelling in the hands and legs in early pregnancy

(Source: American Pregnancy Association)

Complications Associated with TTTS

  • Premature labor either due to ruptured membranes or induction
  • Respiratory, digestive, heart, or brain defects in the recipient twin because of excess fluids
  • Donor twin developing anemia
  • Fetal demise/death

(Source: American Pregnancy Association)

Treatments
There are a few options for treatment of TTTS:

  • Watchful waiting to see how the condition progresses
  • Repeated withdrawal of amniotic fluid from the twin with more fluid (Amnioreduction)
  • Creating a small hole in the twins' intervening amniotic membranes so the amniotic sacs can equalize their fluid levels (Septostomy)
  • Selective feticide in order to prevent the loss of both twins or termination of the pregnancy altogether
  • Fetal laser surgery

About fetal laser surgery:
Fetal laser surgery was performed for the first time in Colorado at Swedish Medical Center. The laser procedure involves inserting an endoscope through the uterus into the sac of the recipient twin. Once the shared blood vessels are identified a laser is used to selectively coagulate or break the joined vessels, closing off the blood flow and reversing the condition.

What are the advantages of laser surgery over amnioreduction? Amnioreduction may need to be done repeatedly throughout the pregnancy to maintain proper blood flow in the placenta, while laser surgery usually only requires one treatment.

Swedish's patient Shannon was diagnosed with TTTS in 2007 and decided to undergo the fetal laser procedure. Dr. Heyborne, director of Swedish's Perinatal Resource Center, coordinated with perinatal experts in Utah to perform the surgery at Swedish. Until Shannon's procedure, patients in Colorado needing fetal laser surgery were required to go out of state. Shannon's procedure went very well and today she has two beautiful twin girls.

See Shannon's story on Denver's Channel 7.

Outlook
TTTS can be mild and both twins can fully recover; however, in severe cases the condition is life threatening for one or both twins.

(Sources: The Twin to Twin Transfusion Syndrome Foundation & US National Library of Medicine)

Resources
The Twin to Twin Transfusion Syndrome Foundation
Fetal Hope Foundation
American Pregnancy Association

For additional questions, please contact Swedish's Perinatal Resource Center by calling 303-788-8550.