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Twin-Twin Transfusion Syndrome

It is possible that the main title of the report Twin-Twin Transfusion Syndrome is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.


Disorder Subdivisions

  • None

General Discussion

Twin-twin transfusion syndrome (TTTS) is a rare disorder that sometimes occurs when women are pregnant with identical (monozygotic) twins. It is a rare disease of the placenta, the organ that joins the mother to her offspring and provides nourishment to the developing fetuses. During the development of identical twins, there are always blood vessels in the fetuses' shared placenta that connect their blood circulations (placental anastomoses). In most cases, the blood flows properly through these vessels. However, in twin-twin transfusion syndrome, the blood begins to flow unevenly, with one fetal twin receiving too much blood (recipient) and one receiving too little (donor). The recipient twin may experience heart failure due to continual strain on its heart and blood vessels (cardiovascular system). The donor twin, on the other hand, may experience life-threatening anemia, insufficient nutrition and oxygen due to its inadequate supply of blood. Such an imbalance in blood flow (i.e., twin-twin transfusion) can occur at any time during the pregnancy, including during delivery.

The effects of twin-twin transfusion syndrome can vary in severity from case to case, depending upon when during pregnancy the syndrome occurs, when it is diagnosed, and any treatment that may be given. The cause of this syndrome is not fully understood, although it is known that placental characteristics play an important role.


Twin to Twin Transfusion Syndrome Foundation
National Office
411 Longbeach Parkway
Bay Village, OH 44140
Tel: (440)899-8887
Tel: (800)815-9211

Genetic and Rare Diseases (GARD) Information Center
PO Box 8126
Gaithersburg, MD 20898-8126
Tel: (301)251-4925
Fax: (301)251-4911
Tel: (888)205-2311
TDD: (888)205-3223

Fetal Hope Foundation
9786 South Holland Street
Littleton, CO 80127
Tel: (303)932-0553
Tel: (877)789-4673

For a Complete Report:

This is an abstract of a report from the National Organization for Rare Disorders (NORD). A copy of the complete report can be downloaded free from the NORD website for registered users. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational therapies (if available), and references from medical literature. For a full-text version of this topic, go to and click on Rare Disease Database under "Rare Disease Information".

The information provided in this report is not intended for diagnostic purposes. It is provided for informational purposes only. NORD recommends that affected individuals seek the advice or counsel of their own personal physicians.

It is possible that the title of this topic is not the name you selected. Please check the Synonyms listing to find the alternate name(s) and Disorder Subdivision(s) covered by this report

This disease entry is based upon medical information available through the date at the end of the topic. Since NORD's resources are limited, it is not possible to keep every entry in the Rare Disease Database completely current and accurate. Please check with the agencies listed in the Resources section for the most current information about this disorder.

For additional information and assistance about rare disorders, please contact the National Organization for Rare Disorders at P.O. Box 1968, Danbury, CT 06813-1968; phone (203) 744-0100; web site or email

Last Updated: 3/19/2012
Copyright 1995, 1999, 2007, 2008, 2012 National Organization for Rare Disorders, Inc.

WebMD Medical Reference from the National Organization for Rare Disorders

Last Updated: May 28, 2015
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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