What Is Twin To Twin Transfusion Syndrome?

Twin to Twin Transfusion Syndrome, commonly known as TTTS, occurs in between 10% and 15% of identical twin pregnancies in which both twins share a placenta (monochorionic).

Left untreated, it has a mortality rate of 90 percent - but now the Twins and Multiple Births Association (TAMBA) have launched an appeal to raise awareness of the potentially deadly condition so that it claims fewer lives. So what exactly is the syndrome?

What is TTTS?

Twin to Twin Transfusion Syndrome is a condition which occurs in some monochorionic identical twin pregnancies. It can manifest in varying degrees of severity, from mild - requiring no medical intervention - to severe, which is often fatal.

In basic terms, TTTS mean the blood vessels connecting the foetuses to the placenta are oversupplying one twin with blood and under-serving the other.

As a result, the weaker twin may develop more slowly than usual as a result of the restricted access to blood, while the stronger twin is at risk of heart failure due to the strain of excess blood.

As mentioned above, with treatment TTTS is non-fatal in 70 percent of cases, although it may cause health problems after birth.

How common is it?

TAMBA estimates that between and 10% and 15% of pregnancies with monozygotic twins (that's identical to you and me) who share a placenta are affected by TTTS. The majority of identical twins (around 75 percent) share a placenta, representing around 0.3 percent of all pregnancies.

What are the symptoms?

Common symptoms that TTTS may be affecting a pregnancy include:

- sudden weight gain and/or painful back and legs (both due to excess amniotic fluid being produced by the dominant twin)
- breathlessness and/or palpitations
- thirst
- spotting
- feelings of early contractions

However, if you are pregnant with monochorionic identical twins, your doctor should already be monitoring you and your babies for any signs of TTTS.

How is it treated?

Mild cases of TTTS may require no medical treatment, only close monitoring to ensure the condition does not worsen.

If it is decided that treatment is advisable, it can either come in two forms:

An amnioreduction, which involves draining off excess amniotic fluid using a needle inserted into the abdomen. It isn't a cure for TTTS, but it should reduce pressure inside the womb and stabilise the pregnancy. If fluid begins to build up again, the procedure may need to be repeated.

Laser ablation is currently the most effective treatment for TTTS. A fetoscope (small telescope) with an attached laser fibre is inserted into the womb, and the blood vessels connecting the foetuses are sealed off by the laser.

In extreme cases, parents may be advised to terminate one twin. Although the decision to cut off the 'donor' baby's cord in the womb is a devastating one, in rare cases it may be advised to give the other twin a better chance of life.

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