Identical twins Nancy and Margo benefitted from the procedure while in the womb as part of a world-first medical trial.

A pioneering procedure using high-powered sound waves has the potential to treat identical twins affected by a serious but rare condition during early pregnancy, a study has found. Blood flow between babies with twin-to-twin transfusion syndrome (TTTS) is uneven, leaving one baby dangerously small and the other too large, putting their survival at risk. Brioney Garrett's identical girls' lives were in danger during her pregnancy before doctors at a London hospital used the treatment to seal blood vessels causing the problem, without needing an operation. Following the world-first treatment, Nancy and Margo were born healthy and, now aged four, will soon start school. Half of the 10 women who took part in the trial required further treatment, and 12 of 20 twin babies survived following the treatment, as reported in the American Journal of Obstetrics & Gynecology, external. The researchers, from Queen Charlotte's and Chelsea Hospital, said it was "extremely exciting" to have a non-invasive method to treat the condition, without the need to put a needle or telescope into the mother's tummy. But before the procedure can be offered more widely, larger studies on more pregnant women are needed to show it can be an effective treatment. "We were in a very dire situation and I don't forget that," she said. "It stays with me always how things could have been. Every day I still count my blessings."