In fetal transfusion syndrome, the donor twin is usually born smaller, anemic, and dehydrated while the recipient twin is born larger and polycythemic, with too much blood volume and increased blood pressure.

Both infants may have problems depending on the severity of the transfusion -- one from an inadequate blood volume, and the other from too much blood. The donor twin may need a blood transfusion, while the recipient twin may need blood volume reduction.

Because of the increased blood volume, the recipient twin may develop cardiac failure and also require medications to strengthen heart function.

• Unequal size of identical twins (discordant twins)
• Pallor (paleness) in the smaller twin and plethora (redness) in the larger twin

Both of the twins will receive the following tests:

• CBC to check hematocrit
• Chem-20 to evaluate electrolytes
• PT and PTT (clotting studies)
• Chest x-ray

The goal of treatment is to treat each child's problem. The donor twin may be anemic enough to need a blood transfusion. The recipient twin may need to have the volume of fluid reduced (this may involve a exchange transfusion).

Medications, such as furosemide (Lasix), and, rarely, digitalis (digoxin), may be used as supportive treatment. A digoxin level may be tested at regular intervals if this medication is needed to treat heart failure in the recipient twin.

If the twin-to-twin transfusion is mild, full recovery is expected for both babies. However, severe cases may result in the death of a twin.

This condition is usually diagnosed at or shortly before the time of birth.