You may want to search the forums at http://www.ubpn.org
for all kinds of information about shoulder dystocia. These people had babies with the birth injury that commonly occurs from problems about shoulder dystocia, so they are experts. I would have thought they would suggest cesareans for everyone, but their responses are significantly more thoughtful.
I do have one friend who had a first baby with shoulder dystocia, but after a lot of difficulty, her skilled midwife managed to get the baby out safely. She moved to another state, and had another midwife. During the second pregancy, she had dreams about having a cesarean, but she was committed to natural birth so she stayed with the new midwife.
Sadly, this baby did have shoulder dystocia and was not able to extricate the baby without serious injury.
That's how I know about the ubpn.org. So -- in her case, she was having dreams about it and things -- maybe it was a coincidence, but maybe she had an intuitive knowing on some level.
I guess my point is to listen to your own body's intuition and try to get a feel that way. I know it's not very scientific, but maybe you can get a sense for yourself. You can also find all kinds of information on the subject on those forums, including plenty of posts from women who had babies with birth injuries from shoulder dystocia the first time but elect to have natural childbirth the second time.