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What is twin-to-twin transfusion syndrome?
TTTS is condition if identical twin pregnancies where both babies share the same placenta. Connections between the babies within the placenta are common, and usually balance each other out. On occasions the connections are unbalanced and one baby ends up losing blood chronically into his or her sibling. The baby losing blood is called the donor, and the one receiving the blood is called the recipient.
Over time the donor becomes dehydrated and fails to grow properly. The amniotic sac for the donor becomes empty and the membranes wrap closely around the baby. At this point the donor is sometimes called the "stuck" twin, because he or she cannot move freely.
The recipient, on the other hand, becomes over-hydrated and swollen. His or her amniotic sac becomes over-full of fluid (polyhydramnios) and the uterus may become very distended. The recipient eventually develops heart failure when he or she can no longer cope with the extra blood volume.
How common is it?
Twins occur naturally in 1 in 84 pregnancies. About one third of twins are identical and two thirds of them share the same placenta. 10-20% of these twins end up with some degree of unequal sharing of blood. For 2000 pregnancies, therefore, one may have twin to twin transfusion syndrome.
How is it diagnosed?
TTTS is usually diagnosed early in the pregnancy by ultrasound. The characteristic appearance of low fluid in one sac (oligohydramnios) and excess fluid in the other (polyhydramnios) must always be present. As the condition advances, the bladder of the donor becomes too small to see, and blood flow in the umbilical cord and heart of the babies becomes abnormal. In advanced cases the recipient appears swollen (hydrops) and one or both of the babies may be dead.
What is the outcome?
Without treatment the babies die in 80-90% of cases. The outcome is dramatically improved with treatment.
Are there any treatments available?
There are a number of proposed treatments for TTTS.
Because the outcome has the potential to be so poor, many families opt to terminate their pregnancy if a severe early case of TTTS is diagnosed. Alternative therapies are available that attempt to either equalize the pressure between the two sacs or interrupt the connection between the babies. These therapies will be described below and are:
1. Aggressive reduction amniocentesis
2. Septostomy, and
3. Selective laser ablation of the connecting vessels.
Aggressive reduction amniocentesis
Selective laser ablation of the connecting vessels
The link below will take you to a slide presentation about laser ablation therapy, its outcomes and advantages: Minimally Invasive fetal therapy
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