A UK-led research team has reported that a non-invasive ultrasound procedure may offer a new way to treat twin-twin transfusion syndrome, a rare but serious complication that can threaten the lives of identical twins sharing a placenta. The early-stage study, funded by the Medical Research Council and led by researchers at Imperial College London and Imperial College Healthcare NHS Trust, found the approach to be safe in the first human trial of its kind.
Early results from a world-first trial
Published on 10 July 2026, the study tested high intensity focused ultrasound, or HIFU, in 10 women from the UK and Europe between 12 and 17 weeks of pregnancy. The procedure used Doppler ultrasound to locate the tiny placental vessels that connect the twins’ circulations, then applied a beam of high-energy sound waves from outside the body to heat and block those vessels.
Researchers said the treatment successfully blocked blood flow in 90% of the placental blood vessels treated. No adverse side effects were reported among the women and unborn twins involved, and 18 out of 20 pregnancies were still healthy two weeks after treatment. The team described the findings as an important proof of concept, while stressing that the study was designed to assess safety and feasibility rather than clinical effectiveness.
A condition with limited options
Twin-twin transfusion syndrome affects between 10% and 15% of identical twins who share a placenta, which the MRC says amounts to between 300 and 400 pregnancies each year in the UK. The condition occurs when blood flow between the babies becomes unbalanced, leaving one twin with too much blood and the other with too little. If left untreated, it can lead to organ failure and, in the most severe cases, the death of one or both babies.
At present, the standard treatment involves inserting a fetoscope into the womb and using a laser to block the shared blood vessels on the placenta’s surface. While often effective, that approach requires a small incision in the mother’s stomach and can damage the amniotic sac, creating a risk of miscarriage.
What the researchers say comes next
Professor Christoph Lees, who led the study, said the findings are encouraging because they show the non-invasive procedure can be used safely in twin-twin transfusion syndrome. He said the team now hopes to follow the feasibility study with a larger clinical trial involving 50 to 100 women to determine whether the treatment can successfully improve outcomes.
The researchers also noted that the study was not designed to test real-world efficacy, and that half of the women still required further treatment, including laser ablation. That means the results do not yet prove the HIFU approach can replace existing care, but they do suggest a possible route to earlier and less invasive intervention.
A possible shift in fetal medicine
For clinicians, the appeal of HIFU lies in the possibility of treating TTTS without an incision and before the condition progresses further. For families facing a diagnosis early in pregnancy, that could matter greatly. One participant, Brioney Garrett from Cornwall, said the trial gave her family “much-needed hope” after learning that laser treatment would not be an option.
The study adds to a broader stream of UK life sciences research aimed at moving promising technology from the lab into the clinic. If larger trials confirm the early findings, HIFU could become a new option for a condition that currently leaves doctors with limited choices, especially in early pregnancy. The team says the next phase will determine whether the method can reverse or improve TTTS well enough to be offered routinely to patients.
