Parents worried about the possible closure of a specialist children's heart surgery unit in Southampton will attend a public meeting later.
A national review wants to reduce the number of centres providing treatment and create larger teams of experts.
The NHS National Specialised Commissioning Group will advise which of the 11 centres should stop doing surgery or which should be expanded.
The results of the study are expected to be published later this year.
Sam Prior, from Locks Heath, who has an eight-year-old son born with a missing left ventricle muscle, is worried that they will have to travel to Bristol for his treatment if the unit closes.
She said: "Every parent would say they would travel to the other side of the world to get the best treatment for their child, but I firmly believe that that treatment is already available here in Southampton.
"It would be the worst thing to happen if we were lose the world class centre that we already have."
Steve Collins, from the NHS Specialist Commissioning Team, said: "The talk that's around of closures is not helpful.
"What we're looking at is the care that people with congenital heart problems need and have and where these operations should happen."
Up to 200 people are expected to attend the meeting at Southampton Football Club at 1800 BST.
It is the only public meeting to discuss the proposed cuts.
The centre at Southampton General Hospital currently carries out about 350 surgical procedures each year.