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Who Gets TTTS (Twin-to-Twin Transfusion Syndrome)?


Updated October 05, 2008

Question: Who Gets TTTS (Twin-to-Twin Transfusion Syndrome)?
Twin-to-Twin Transfusion Sydrome is a disorder that impacts about ten percent of monozygotic (identical) twin pregnancies. Find more answers to Frequently Asked Questions About TTTS.
Answer: The short answer: TTTS occurs in one third of Monochorionic monozygotic pregnanices. Let's see what exactly that means... Monozygotic, or identical, twins represent about one-third of all twins. These individuals develop from a single fertilized egg that splits several days after fertilization. More than half the time, this occurs four to eight days post-conception, and the two embryos will share a single placenta structure. In most cases, the twins will develop individual amniotic sacs, however, they will be encased within a single outer membrane, called a chorion. This the term "monochorionic" (mono=one, chorionic=chorion). Only monozygotic twins can share a placenta, and only monochorionic monozygotic twins are at risk for TTTS since their circulatory systems may connect through the placenta.

Some statistics from http://www.texaschildrens.org/carecenters/fetalsurgery/twin_twin_transfusion_syndrome.aspxTexas Children's Hospital, one of the leading medical centers in diagnosing and treating TTTS:
  • 2/3 of all identical twin conceptions are monochorionic - or fetuses that share one placenta
  • 10-15% of monochorionic twins are affected by TTTS
  • 1,500-2,000 cases of TTTS occur each year in the U.S., making it more common than SIDS
  • 90% of TTTS cases that go unchecked result in the loss of one or both fetuses.
  • 25% of twins surviving untreated TTTS will experience neurologial compromise.
  • In 60% of the cases of monochorionic twins who receive laser ablation to treat TTTS, both twins survive.
  • 87% of children who received laser intervention to correct TTTS showed normal neurological functions at age 3.

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