Just wanted to c+p this from the Royal College of Midwives 'Normal Birth Campaign' website. It's aimed at midwives and is about trying to increase rates of normal births:
Birth positions
Our upright posture makes us unique amongst mammals. However, this evolutionary development has made giving birth much more difficult for us. And these difficulties can be made much worse when we don't even take advantage of the help that gravity and being able to move around can provide.
From a physiological point of view, lying on one's back to give birth has many disadvantages and few advantages. This supine, 'confined' position, which has been common for the last two hundred years or so, came about for social and historical reasons which are no longer relevant. We continue to use it only from habit and familiarity.
Throughout the ages, and across human cultures, women have preferred to give birth with their bodies vertical. Historical manuscripts often show women giving birth in a standing or squatting position with their legs spread. There is now substantial evidence to suggest that these positions increase the outlet of the pelvis.
Over the last couple of decades, 'alternative' birthing positions have become more popular once more. However, there still seems to be considerable resistance to using them amongst midwives - perhaps because we believe they might expose us to the criticism and censure of our colleagues. These positions can be very beneficial, and should be part of every midwife's repertoire.
How do they work?
The key benefit of upright birthing positions is that they use the force of gravity to assist the descent of the fetus and the opening up of the cervix. They also allow a woman to move around during labour, flexing with the contractions and shifting from side to side to ease the pain. Some positions, such as 'all fours' enable a supporter to massage her lower back or put warm towels on it, which can help to relieve the strain.
If you try out the common positions, you will see how one flows into another - they are not really distinct positions at all. If a woman is familiar with them, she can move from one to another in labour according to her feelings at the time, finding the one that most suits her needs.
Moving around in this way is good for her. In the first stage, she may prefer more upright positions that afford greater mobility, but as she progresses through the second stage she will want to adopt those positions that feel most suitable for bearing down and giving birth.
Tips and tricks
Think about how you can help her to adopt other positions in labour ? observe what works and what doesn't, and review when and why these positions were most successful. Your knowledge of antatomy can also help you to understand how different positions aid the physiological processes (for example, the curve of Carus).
Recommend that the she familiarise herself with different positions ? this is something she can do before labour with her partner or other supporters, and the more familiar she is with them beforehand the easier she will find it to adopt them during labour. Some positions, like squatting, may not come easily to women brought up in the Western world.
Create a secure, private environment - this facilitates a woman's self expression and gives her the freedom to follow her own instincts. The feeling that she is in a private space will help her to feel comfortable trying out 'unconventional' positions."
Want to add - this could not be further from the reality of birth at our local hospital. 85% of women there give birth in minor variations of the same position: on their backs. I think it's really, really cr*p. If I was giving birth for the first time again today I'd be tempted to print this off and make the midwife read it aloud to me on admittance to hospital, just to make sure she'd taken the message on board.