If there is one then it means it could wrap around the baby and cause amputations or deformities of fingers, toes and sometimes even arms and legs. It's a good thing that they don't think it's done that yet and will probably just give you more regular scans to check and make sure it doesn't become attached. If it does then I think there is an operation that can be done to remove it and untangle baby but most people don't find out it's happened until after their baby is born so you're lucky it's been picked up now and can be monitored.
I know all of this because my son was born with the fingers on his right hand not fully developed and they first diagnosed it as ABS. Turns out his wasn't and is actually a sporadic congenital abnormality called Symbrachydactyly.
Good luck with the re scan.. let me know if you want any more info