Twin to twin transfusion syndrome (TTTS) is a rare condition that occurs during a twin pregnancy when blood moves from one twin (the “donor twin”) to the other (the “recipient twin”) while in the womb. TTTS is a complication that specifically occurs in identical (monozygotic) twin pregnancies that share the same “egg” sac (monochorionic) that may or may not share the same amniotic sac (monoamniotic). TTTS usually develops between 15 and 26 weeks of pregnancy. The donor twin may be born smaller, with paleness, anemia, and dehydration. The recipient twin may be born larger, with redness, too much blood, and increased blood pressure, resulting in an increased risk for heart failure. Treatment may require repeated amniocentesis during pregnancy. Fetal laser surgery may be done to interrupt the flow of blood from one twin to the other. After birth, treatment depends on the infant’s specific symptoms. The donor twin may need a blood transfusion to treat anemia. The recipient twin may need to have the volume of body fluid reduced. This may involve an exchange transfusion. Medications may be given to treat heart failure in the recipient twin, per the U.S. Department of Health and Human Services/National Institutes of Health

Approximately 15% of Identical Twin pregnancies develop TTTS.

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