It's amazing what modern medicine can do for these babies nowadays. Even ten years ago, many of these children would have died in the womb, or shortly after birth, but because of the advances in medicine, they are able to be separated and go on to live normal lives.
I wonder about some cases, though. I saw a documentary about a set of conjoined twins who comprised, essentially, a two-headed person with each head controlling one side of the body. Although they both have distinct personalities, likes and dislikes, I have to wonder about their future. Can they ever really lead a normal life? I don't know what you do in a case like this. The medical ethics involved are staggering.