A High Court ruling has raised uncertainty over Government plans to introduce "long overdue" changes to children's heart surgery services across the country.
A judge quashed part of an NHS consultation process vital for introducing the re-organisation.
Last July the Joint Committee of Primary Care Trusts (JCPCT) selected seven specialist centres for the future delivery of paediatric cardiac surgery in England.
It chose centres at Great Ormond Street and the Evelina Children's Hospital in London, as well as Newcastle's Freeman Hospital, Birmingham Children's Hospital, Alder Hey in Liverpool, the Royal Children's Hospital in Bristol and Southampton General.
The controversial decision, if it stands, means the closure of units at Leeds General Infirmary, Glenfield Hospital in Leicester and London's Royal Brompton.
The reconfiguration was the result of the Safe and Sustainable NHS review, which was triggered by the Bristol heart scandal in the 1990s in which 35 babies died and dozens more were left brain-damaged. The aim of the review is to provide fewer but more efficient units round the country.
Mrs Justice Nicola Davies, sitting at London's High Court, allowed a challenge against the Leeds unit closure and declared the decision-making process "legally flawed".
She said there had been "a fundamental unfairness" in the consultation process. The judge emphasised that she was not ordering that the whole consultation process had to be re-run.
Lawyers involved on either side of the challenge are now considering the full impact of her ruling - and there is disagreement over the extent to which reconsultation and reconsideration must take place.
The judge's decision was a victory for Save Our Surgery (SOS), which represents some 600,000 residents in the Leeds area fighting to keep their unit open. SOS believes the ruling means that all the hospitals that face losing their children's units will now be able to fight again retain them.