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"Your pelvis may be too small"

"Your pelvis may be too small" is a particularly poor excuse for not supporting a woman who intends to have a home birth. In the extremely unlikely event that her pelvis really is too small, and she is at home, her labour simply will not progress. She will labour on in her own time, and eventually, when she gets fed up of it, she will transfer to hospital for the inevitable C-section.

Where cephalo-pelvic disproportion (CPD) occurs, there just isn't room for the baby to move through the pelvis... so things don't progress, and a CS is needed. In places where the mother has no access to medical attention, this can be tragic - resulting in an obstructed labour that lasts for days and days, concluding with a dead baby and a mother with a fistula or worse. But this has precisely zilch to do with women planning a home birth in a developed country.

At least if you start off at home, you know that there is less chance that your 'failure to progress' was really a 'failure of the hospital environment to make you feel at ease'; less chance that it was due to lack of mobility or being stuck on your back/propped up on a monitor; less chance that it was due to infection risk in hospital and arbitrary time limits being set on your labour there. And if the slow progress was due to the baby's head being slightly misaligned - eg asynclitic (tilted to one side, maybe ear presenting first) - then the journey to hospital might just jolt it back into position!

Now consider what would be different if you abandoned plans for a home birth because your pelvis 'too small'.

You go to hospital in labour, maybe feeling disappointed. You hang around for a while. If labour doesn't progress at the rate your caregivers would like, they may suggest an oxytocin drip. This will drive your uterus harder, but if there is true CPD, no amount of oxytocin can make that baby pass through your pelvis. So you will be in more pain, as accelerated labours are usually more painful - the cascade of interventions will have started - you will probably want an epidural. Labour still won't progress.

Maybe you will worry then that, if you'd been at home and relaxed, things might have been better. You will never know. Maybe you will worry that the epidural is slowing things down. You will never know. If you reach full dilation, forceps or ventouse may be attempted - but if there is true CPD then you will end up with a CS. The only difference is that you may well wonder whether it would have happened, if you had gone ahead with that home birth.

It is often said that "the only good pelvimetry is a baby's head" - ie there is no point trying to measure the dimensions of a woman's pelvis, because the only way of knowing whether the baby can pass through it, is for her to labour.

Remember that pelvic ligaments are stretchy, allowing your pelvis to open up to allow your baby through; your baby's head moulds, allowing it to fit through; and remember too, that apart from the past 50 years or so when CS has become an option, every single one of your female ancestors has clearly had a baby which passed through her pelvis, and lived to tell the tale. I think that 220 million years of mammalian evolution speaks pretty loudly.

And to finish off... there is a wonderful article by birth attendant Gloria Lemay, Pelvises I Have Known and Loved (www.birthlove.com/pages/gloria.html)

This page updated 15 October 2001

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