My sister had 5 back to back. If she gets pregnant again her doctor told her she wouldn't make it. But that's just because she didn't wait a few years in between each child for her body to heal properly.
3 is what that they deem safe, but as long as you are healthy and the scar tissue is ok you can have as many as you like, I just had my fourth and last and I know a mom who has had 6.
they advise not more than 3 but if u get pregnant they have 2 take care of u..i have had 4