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Twin-twin transfusion syndrome: developing a new way to help babies who are struggling in the womb

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What did the project achieve?

“The results from pre-clinical experiments show that our new ultrasound-based technique appears to be effective – and, importantly, has few side effects,” says Professor Christoph Lees of Imperial College London.

Twin-twin transfusion syndrome (TTTS) is a serious condition that affects around one in 10 identical twins who share a placenta.1 Caused by abnormal connections developing between placental blood vessels, it can be extremely dangerous for both babies – potentially leading to premature birth, death and disability.

Laser treatment to block the affected blood vessels is an option. However, as this involves surgery inside the womb, it carries a risk of serious complications such as early labour, miscarriage or infection. So this procedure is only offered in the most severely affected pregnancies.

Professor Lees and his team are developing a new treatment for TTTS using a type of ultrasound called high-intensity focused ultrasound (HIFU) to block blood vessels in the twins’ shared placenta. As this new approach does not involve surgery, it could offer a safer alternative to laser therapy.

“We have now demonstrated that we can successfully block the blood flow in placental blood vessels using HIFU in pre-clinical experiments,” says Professor Lees.“We have several more steps to go but guided by these encouraging results, we have secured funding of over £2 million from the Medical Research Council to carry out a clinical trial in pregnant women that we hope to launch in 2020.” 


1. NHS website: Antenatal care with twins https://www.nhs.uk/conditions/pregnancy-and-baby/antenatal-care-twins/#ttts [website accessed 25 October 2018]

This research was completed on

Estimates suggest that around 10 per cent of identical twins develop a serious condition called twin-twin transfusion syndrome (TTTS), which strikes while babies are in the womb.1-3 This condition can be very dangerous for babies, causing premature birth, death and disability. Professor Christoph Lees, of Queen Charlottes’s and Chelsea Hospital, Imperial College, London, is investigating whether treatment with a powerful form of ultrasound has the potential to help babies during pregnancy. The ultimate aim is to prevent premature birth, save babies’ lives and protect them from disability – and spare parents from anxiety and heartache.

How are babies’ lives affected now?

“When identical twins develop TTTS during pregnancy, blood moves from one baby to the other via connections in their shared placenta,” explains Professor Lees. “One twin can become perilously short of fluid and the other dangerously overloaded.”

“If left untreated, babies with TTTS can lose their lives,” continues Professor Lees.4 “Babies are also at risk of being born very early, which brings its own dangers. Those who survive pregnancy can be unusually small at birth, with anaemia, or they can develop heart failure or brain damage.”

Pregnant women whose babies develop TTTS are monitored closely and can be offered treatment – often laser therapy. “Although laser therapy boosts babies’ chances of survival, it involves potentially risky surgery during pregnancy,” says Professor Lees. “Complications include miscarriage, premature birth and infection, so laser therapy is only suggested if TTTS is severe enough for benefits to outweigh risks.”


How could this research help?

Professor Lees’ team is in the laboratory stages of developing a new treatment for babies with TTTS using a type of ultrasound, called high-intensity focussed ultrasound.

The idea behind this new treatment – like laser therapy – is to stop blood from moving between identical twins in the womb by blocking blood vessels in their shared placenta.

“Laser therapy involves surgery: the mother is given a local anaesthetic and a needle is inserted through the abdominal wall and into the womb,” explains Professor Lees. “The invasive nature of this surgery can lead to serious complications.”

“As the new ultrasound treatment that we are hoping to develop does not involve surgery, we believe it could be safer than laser therapy – although we can’t be sure, as our treatment is not yet ready for clinical use. In theory though, an ultrasound treatment could mean more babies with TTTS could be treated earlier in pregnancy, hopefully improving their chances of surviving and escaping disability."


1. Lewi L et al. The natural history of monochorionic twins and the role of prenatal ultrasound scan. Ultrasound Obstet Gynecol 2007; 30(S): 401.

2. Duncan KR et al. The aetiology and management of twin-twin transfusion syndrome. Prenatal diagnosis 1997; 17:13: 1227-36.

3. NHS Choices. Have a health pregnancy with twins or more. http://www.nhs.uk/conditions/pregnancy-and-baby/pages/twins-healthy-mult... Website accessed 3 January 2014.

4. Senat M-V et al. Endoscopic laser surgery versus serial amnioreduction for severe twin-to-twin transfusion syndrome. NEJM 2004; 351: 136-44.



Project Leader Professor Christoph C Lees MD MRCOG MB BS
Project Team Professor Dino A Giussani PhD BScDr Gail R ter Haar DSc PhD MA MScDr I H Rivens PhD ARCS
Project Location Centre for Fetal Care, Queen Charlotte's and Chelsea Hospital, Imperial College London
Project Location Other Department of Fetal Medicine, Addenbrookes Hospital, CambridgeDepartment of Physiology, Development and Neuroscience, University of CambridgeJoint department of Physics, Institute of Cancer Research (ICR), Royal Marsden Hospital
Date awarded 9 October 2013
Project start date 1 January 2014
Project end date 31 July 2016
Grant amount £102,258
Grant code GN2052


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