Twin-to-Twin Transfusion Syndrome
Twin-to-twin transfusion syndrome (TTTS) is an uncommon pregnancy complication that occurs in developing identical twins.Identical twins who share the same placenta in their mother’s womb are referred to as monochorionic twins. The placenta is attached to the mother’s uterus and provides essential nutrients and oxygen to each baby through the umbilical cords. Twin-to-twin transfusion syndrome (TTTS) occurs in a monochorionic pregnancy when blood vessel connections in the placenta are not evenly distributed, causing an unequal exchange of blood between babies. Fraternal twins are not at risk for TTTS since they don’t share a placenta.
In TTTS, the “donor” twin gives away more blood than it receives, increasing the risk of organ failure and malnutrition. The donor twin may also lose blood volume (hypovolemia), which can cause low amniotic fluid levels and bladder abnormalities. Meanwhile, the “recipient” twin receives too much blood and experiences increased blood volume (hypervolemia), potentially leading to cardiovascular dysfunction and heart failure.
Twin-to-twin transfusion syndrome usually takes place between 16 and 26 weeks in a woman’s pregnancy. It is believed to occur at random in about 15% of women with monochorionic pregnancies, as there is no clear genetic or external cause of TTTS.
A woman pregnant with babies who have twin-to-twin transfusion syndrome may experience:
- A sudden increase in weight
- Rapid womb growth
- An especially large uterus
- Swelling in feet or hands early in pregnancy
- Abdominal pain, tightness or contractions unrelated to labor
A physician may identify signs of twin-to-twin transfusion syndrome during a pregnancy ultrasound. Possible indicators of TTTS on an ultrasound image include:
- A noticeable size difference between twins of the same gender
- A noticeable size difference between the babies’ amniotic sacs or umbilical cords
- Evidence of congestive heart failure in the recipient twin
- Excess amniotic fluid in one twin and too little amniotic fluid in the other
Recent advancements in twin-to-twin transfusion syndrome treatment have significantly improved outcomes for babies facing this condition. Tampa General Hospital’s Women’s Institute offers highly specialized care for TTTS, including amniocentesis to improve blood flow in the placenta and remove excess fluid, as well as laser surgery to seal off connecting blood vessels between twins. In other cases, early delivery may be recommended if a woman’s babies are sufficiently mature.