This isn't quite true Brian.
The GPEW do not criticise the use of live-saving medical interventions. They criticise the use of C sections where their use is not clinically indicated. This position flows from the evidence provided by WHO and NICE. That evidence shows that an overuse of interventions are too often due to a number of factors - one of which it that maternity units are too often too understaffed to support vaginal birth in all cases.
C-section exposes birthing women to increased post natal risks and harms. To use surgeries due to overcome shortages or similar such reasons is an abuse, depriving women of bodily autonomy for vaginal birth.
My wife is a midwife and has been for over 25 years. I am not one myself but obviously we talk.
C Section is often the go to for any doctor who is a little uneasy with the way any birth is going will opt for C Section. Situations where proper "normal birth" management are implemented will often negate any risk perceived by a doctor.
The fear of litigation is a driving factor
The post section risks to the mother can be greater than any risk to mother and baby of a normal birth.
I don't think there is any other example in the NHS where one can elect for surgery when not needed. Consider going in to A&E with stomach pain and insisting on having your appendix out . . . it would not be entertained and yet C Section is something any mother can opt for.
Not only are there arguments on the medical and moral fronts, but the cost of C Sections (greater than 50% of births in some trusts I believe) involving surgeons, anesthetists, nurses, time in hospital etc etc is huge when compared to a "normal" vaginal birth and a significant unnecessary cost to the NHS.
There are, of course, very legitimate and necessary reasons for some C Sections but I believe these to be a small proportion of those carried out.
Given what I believe the present situation to be, this seems a logical and financially sensible policy from the Greens.