Twin-to-twin transfusion syndrome (TTTS) is a rare condition that occurs only in identical twins while they are in the womb.

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Causes

TTTS occurs when blood moves from one twin to the other. The twin that loses the blood is called the donor twin. The twin that receives the blood is called the recipient twin.

Both infants may have problems depending on the severity of the transfusion. The donor twin may have too little blood, and the other may have too much blood. The donor twin may need a blood transfusion, while the recipient twin may need to have the amount of blood in his or her body reduced.

Symptoms

The donor twin is usually born smaller than the other twin, usually with paleness, anemia, and dehydration.

The recipient twin is born larger, with redness, too much blood, and increased blood pressure. Because of the increased blood volume, the recipient twin may develop cardiac failure and also require medications to strengthen heart function.

The unequal size of identical twins is referred to as discordant twins.

Exams and Tests

This condition is usually diagnosed by ultrasound during pregnancy.

After birth, the infants will receive the following tests:

• Blood clotting studies, including prothrombin time (PT) and partial thromboplastin time (PTT)
• Comprehensive metabolic panel to determine electrolyte balance
• Complete blood count
• Chest x-ray

Treatment

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.

Outlook (Prognosis)

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.

Alternative Names

TTTS; Fetal transfusion syndrome

References

Habli M, Lim FY, Crombleholme T. Twin-to-twin transfusion syndrome: a comprehensive update. Clin Perinatol. 2009 Jun;36(2):391-416, x.

Cunningham FG, Leveno KJ, Bloom SL, et al. Multifetal gestation. In: Cunnigham FG, Leveno KL, Bloom SL, et al, eds. Williams Obstetrics. 23rd ed. New York, NY: McGraw-Hill; 2010:chap 39.

Updated: 4/12/2012

Reviewed by: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine; Susan Storck, MD, FACOG, Chief, Eastside Department of Obstetrics and Gynecology, Group Health Cooperative of Puget Sound, Bellevue, Washington; Clinical Teaching Faculty, Department of Obstetrics and Gynecology, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.