If it was someone I didn't know very well, and only chatted to in passing then I wouldn't have said anything personally, as she has her midwife to discuss her pain relief etc with.
If it was someone I knew well who had ASKED me what I thought of it, then I would have told her what I know, and also state it is limited knowledge and advise her to seek the full facts from her midiwfe.
In either situation though I wouldn't give my opinion on it, as it is ust that...my opinion, and I feel there is a time and a place for it.
Not having a go crazy mofo, just saying what I would do.