Has there ever been a case where a surrogate mother didn't want to give the baby to the parents?

I know I couldn't be a surrogate mother because I would get attached and wouldn't want to let go of the baby. So has there ever been a case like this? Is there some sort of contract when becoming a surrogate mother? I don't know too much about it.Has there ever been a case where a surrogate mother didn't want to give the baby to the parents?
One of the first cases of it, the "Baby M" case back in the 80s gained a LOT of attention because she wanted to keep the baby.