Twin-to-twin Transfusion Syndrome (TTTS)

Twin-to-twin Transfusion Syndrome (TTTS) is a rare but life-threatening condition that affects 10 to 15 percent of identical twins that share a placenta (monochorionic twins). TTTS can also occur in triplet or higher order pregnancies with monochorionic twins.

TTTS can have serious consequences to the babies so you will need to be monitored very closely by your doctors.

What is Twin-to-twin transfusion syndrome (TTTS)?

Twin-to-twin transfusion syndrome (TTTS) is a rare, but potentially fatal, condition that affects about 10-15% of twins that share a placenta (monochorionic twins), as well as higher order pregnancies with a shared placenta
It can appear at any time during pregnancy, but most commonly before 24 weeks’ gestation
It arises because there are blood vessels connecting the placenta that the twins share. Usually, these blood vessels allow blood to flow evenly between the babies so that each baby receives the same amount. However, in TTTS, part of the blood flow is diverted from one ‘donor’ twin to the other ‘recipient’ twin in what is effectively a blood transfusion (hence the name)
A lack of blood supply can affect the donor twin’s growth so they are smaller than average. The recipient twin is usually larger and has a higher blood volume, which can strain their heart as it works harder to pump the extra blood
To compensate for the excess blood, the recipient twin often produces a large amount of urine which is then passed out as amniotic fluid (the water around the baby). In contrast, the smaller donor twin can have a reduced amount of amniotic fluid; occasionally it can become stuck against the wall of the womb if there’s very little surrounding fluid

Who does TTTS affect?

TTTS only affects twins, triplets or more who share a placenta. Twins with a shared placenta are referred to as monochorionic twins because they share an outer membrane (chorion)

What are the warning signs?

During your first ultrasound scan, the sonographer will look carefully to see if your twins are monochorionic or dichorionic
If they are monochorionic, or you have monochorionic or dichorionic triplets, they should be closely monitored with ultrasound scans, so that if TTTS starts to develop it is diagnosed and suitable treatment considered

What symptoms should I look out for?

Sudden weight gain due to excess fluid – getting noticeably bigger in a short space of time, sometimes even within 24 hours
Being breathless at rest and having palpitations (unusual heartbeats)
Feeling that your tummy is tight, uncomfortable and/or the surface looks shiny
Increased thirst
Feeling early contractions
Back pain and leg pain due to the build-up of fluid

For further information please download our Complications Guide, which is designed to help you to understand some of the conditions associated with twin, triplet and higher-order pregnancies.

Understanding TTTS and the Laser Therapy Treatment Option

Illustrating TTTS in Twin and Triplet Pregnancies

The video and diagram are supported by the GIFT-Surg international research project, which is funded by the Wellcome Trust and EPSRC.

If you are worried please talk to your midwife and doctors as they are best placed to explain your situation and treatment options for you.

Our Twinline listening service can provide a reassuring listening ear so you are not alone but we do not provide medical advice.