At what stage would you have a cannula? Fair enough you don't want one. Me I'd prefer it there as a just in case I needed it later. In the case of life and death or serious illness they can take up precious minutes putting one in especially if your compromised making it harder to get in (like your haemorraging or something) and you can't guarantee someone experienced in getting them in will be there all the time.

As a midwife I would respect your decision not wanting it in but to cover myself I would have to document it in the notes that the client was refusing and the reasons behind that. Of course I would let the person know I was doing this not that I didn't agree with them just to protect myself. I would imagine the Obstetrician would do the same if you said no and of course are of sound mind so can not be made to have it in. I would say most reasonable health professionals would except your decision after telling you why they would want it there and then would cover themself incase something happened and an inquest was looking into what could have been done differently to chance the outcome.

In the event you did walk out depending on the circumstance (say your in labour and didn't want one in and said you were off to have a free birth at home) then legally the department of community services would be called and a report would be made to say that the medical staff did not think you were protecting your unborn child and they believed they were at risk of serious harm (in the case of failing to provide medical care) I am going to all extremes here. No one can hold you against your will except in the event they believe your not of sound mind but if a mandatory reporter (such as nurse or Dr) thought you were putting your baby at risk they would most likely report it (and nothing would probably become of it). A report wouldn't mean you would have the police on your door step dragging you back against your will.

The hospital were I work with have policies that we have to stick to. For a VBAC our policy is that continuous monitoring, a cannula is in place and a few other stipulations. If this is not done and say something happened like your baby was distressed and an emergency c/s needed to occur and say bub had some sort of disability (again going to the extreme) then that would come back to bite us if an inquest happened into the cause. Now this is going to the extreme I know but just outlining why these policies are in place. Unfortunately most maternity hospitals are medically based and don't protect the natural phylosophy of labour and birth.

If a health professional was following policy and you refused and knew the pro's and con's and were of sound mind when you made your decision then if it all went to court over something happening to you or bub then if it was documented that would cover them against medical negligency so to speak.

Once again I am going to the extreme but just thought I would add what would happen if that happened where I worked. The chance of this happening would be very low. Much more likely to come in in labour refuse a cannula have a troublefree birth, no complications, no need for a cannula.