Twin-to-Twin Transfusion: What You Need to Know
Every couple experiencing a multiple gestation needs to be aware of the condition known as Twin to Twin Transfusion Syndrome (TTTS). This is a disease of the placenta which occurs in identical twin pregnancies, but may also affect higher order multiples (Triplets, Quads, etc.) if there are identicals present within it. It does not occur in Fraternal Twins. However, unless you know the twins are boy/girl, it would be best to assume they are identical and monitor for TTTS unless it is proven otherwise before delivery. While considered rare, this is a highly lethal condition which affects up to 6000 documented cases a year, and without treatment may be 80-100% likely to result in the death or major disability of one or both twins. Treatments that are currently available can increase the odds of survival for both twins to as much as 60-70%, but are useless if the condition goes undiagnosed. The most likely type of identical twins to be affected by TTTS (up to 15% more likely) are those diagnosed as Monochorionic/Diamnionic. This diagnosis may be obtained via Ultrasound. It is made when there is only one placenta evident, and a very thin amnionic separation with no chorionic separation observable. This can be seen very early on in a pregnancy, even before sex may be determined. Establishment of choronicity early on is invaluable, as this allows time for education about TTTS, and the need for close monitoring. If choronicity cannot be established, yet the twins are found to be of the same sex, it would still be prudent to monitor closely for TTTS. Once a diagnosis of Monochorionic Twins is made, it is imperative that the parents be made aware of the risks and warning signs of the onset of TTTS. Close monitoring via Ultrasound (as close as one every two weeks) is necessary to diagnose the onset of the condi! tion as early as possible.
TTTS is a disease of the placenta in which the twins share blood vessels. It can occur at any point in the pregnancy, even up to the moment of delivery. In it's most common form, the shared blood vessels may result in one twin (donor) not gaining enough nutrition, while the other (recipient) gets too much. This can cause a build up of fluid around the recipient twin, while the donor may have very little amnionic fluid. The donor is usually smaller, and likely to be anemic. The recipient can be subject to heart failure due to the fluid overload. Depending upon the severity of the transfusion, one or the other twin may die in-utero. The surviving twin then is at risk of a "reverse" transfusion which may also result in death or severe neurological damage. This is thought to occur in up to 25% of these cases.
In most TTTS affected pregnancies, the excess fluid build up may cause premature labor and rupture of membranes. This often results in extremely premature delivery and survival can depend upon the gestational age at the time, and luck. Currently available treatments may buy time for twins that are not yet viable, or precious days for viable, but very premature babies. This is a disease where often chances for survival are better for the babies to be born, even prematurely, than to continue to be subject to the ongoing transfusion.
Should you be diagnosed with Monochorionic Twins, or a TTTS onset, you will find the links below to have much of the information you will need (including links to other sources) in order to make informed decisions about which treatment options and care you may choose to pursue:
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The Twin to Twin Transfusion Syndrome Foundation
eMedicine - Twin-to-Twin Transfusion Syndrome : Article by Terence Zach, MD