We've attended a number of antenatal classes lately. One major focus of these is the labour process, explaining methods of relaxing and how to help manage pain. We were taught breathing exercises, focussing on breathing out (similar to coping techniques for an asthma attack). Various active labour positions were shown to us, as the TV sterotype of lying on your back with legs akimbo is pretty much the worst position for childbirth.
One major benefit of these classes is that it gave me the sense that I have an active and beneficial role to play, rather than just sitting there like a lemon for hours holding Katherine's hand saying muttering vague sympathies and wondering if the bloke's role should be to pace up and down the corridor smoking cigars...
I digress. So far, the advice given is all good common sense stuff that's well backed up physiologically.
However, some other advice about pain relief made my sceptical eyebrow raise. The teacher at the NCT (National Childbirth Trust) class recommended arnica tablets as a pain relief (though the NHS classes made no mention of this). I didn't think any more of it until Katherine bought some on a shopping trip with a friend. They turn out to be a homeopathic remedy (i.e. sugar pills). All the research I can find shows them to be nothing more than placebos as would be expected if you think about it (for example - http://archsurg.ama-assn.org/cgi/content/full/133/11/1187). Now you might think that a placebo has a strong effect (and indeed it is), but at over £5 for a small tub of tablets it's just a plain rip off. I may as well give Katherine some mints.
Another method of pain relief that is on potentially dodgy scientific ground is TENS, which consists of a small machine with four electrodes on wires that are placed on particular places on your back. The machine sends pulses at certain frequencies that are said to "block" your pain transmitting nerves (though why this has no effect on other nerves with jobs such as motor or temperature sensing I have no idea). This was recommended by both the NCT and the NHS.
The research into the effectiveness of TENS for childbirth seems inconclusive. I'm not sure I quite believe the pain blocking theory of operation, but perhaps a better theory is that TENS performs a bit of neurological slight of hand. The tingling sensation could be enough to distract the brain. The human brain can only process so much information at once, so the pain is felt less strongly.
It is (to me) quite surprising given how much TENS was emphasised by the teachers as a good therapy (especially by the NHS who really should know better about clinical trials). However, neither therapy seems to do any harm, which is why I think they're both recommended. I guess a few good placebos are better than nothing.
I think it mostly comes down to the fact that childbirth is not a very predictable or controlled process. It's different for everyone, lasts wildly varying lengths of time, different people have different pain thresholds, etc. Bascially, there are far too many differences to make a good control group for a double blind trial into obstetric pain relief with good methodology. You can't even test the same person through two labours with and without the pain relief because so many other factors will be different that the results would be meaningless.