This is a very interesting thread. I'm still in two minds, having read all of your comments.
I think part of the dilemma comes from birth being both medical (complications) and non-medical (normal low risk birth). And disagreements about where the line is. I don't think there is enough evidence about risk in pregnancy for anyone to be categorical about many situations (although some are clearer) - as people have pointed out the policy on VBACs has changed recently.
So, it's a grey area. And also a sensitive area, with new life involved. And also the only major involvement with the healthcare system many people will have until old age. So 'healthy' people are rightly resentful of being 'medicalised' when they may not feel it's warranted.
Clearly, where the intervention of medical professionals is required they must be allowed to follow clinical procedure - they're trained after all and those procedures are designed to keep us safe. However, the standard rules of informed consent apply just as they would for any other medical intervention.
But I think the above circumstances have to be taken into account - it's unreasonable to expect women to go along with medical advice blindly, a higher level of information is required. It's not like breaking your leg, which is more clear cut. And with that goes greater choice about the outcome.
Do I think women should have absolute choice? Difficult.
To refuse treatment, yes. That's the right of anyone offered medical treatment.
To be supported in a natural birth in order to avoid medicalisation of birth, if medicalisation is not justified? Yes.
To demand treatment? No, as that goes over the line into the medical sphere where I think we need to live by the rules of healthcare provision (unless by exercising the choice to go against medical advice, we waive the right to complain/seek compensation if something goes wrong). There's obviously also a cost lens, funds are not infinite for healthcare.
However, all risk factors being relatively equal, women should certainly have a choice between medical options. And much more needs to be done to take the wishes of women more seriously - there are too many stories of women not being heard when they say their pain is unbearable, or they feel that something is wrong with their labour, or that they are terrified of birth.
I think it's an important debate, because approximately half the population will experience this at least once in their lives and it does have a lot of undercurrents about the wider position of women in society. I don't think the current situation is ideal, so I think we need to keep poking things to improve the situation.