Twin-to-twin transfusion is a condition that can develop in two or more fetuses who share the same placenta. In this condition, abnormal blood vessels develop in the placenta and move blood from one twin to another.

The risks of twin-to-twin transfusion include stillbirth of one or both twins or severe complications in one or both twins after birth.

When blood shifts from one fetus (the donor) through the placenta to the other fetus (the recipient), the donor twin may:

• Be smaller.
• Not have enough red blood cells (anemia).
• Be surrounded by less amniotic fluid.
• Develop heart failure after birth.

The recipient twin may:

• Be larger.
• Have too many red blood cells.
• Be surrounded by too much amniotic fluid.
• Develop heart failure after birth.
• Develop too much bile in the blood (referred to as hyperbilirubinemia or jaundice). Bile comes from the breakdown of excess red blood cells.

Twin-to-twin transfusion is suspected when a fetal ultrasound shows that one twin is much larger than the other.

Treatment can include amniocentesis to remove excess amniotic fluid. After birth, the donor twin may require a blood transfusion while the recipient twin may need to have some blood removed. Both twins may need treatment for heart failure.