A report finding no link between backache and epidural injections used to relieve labour pain has been greeted with scepticism.

Pregnancy groups say they have anecdotal evidence that scores of women have been troubled by a sore back since they were given the painkilling injection.

However, a handful of studies into the issue - the latest of which was published in the British Medical Journal on Friday - has failed to find any such association.

An epidural is a spinal injection which gives longer-lasting pain relief during labour.

A needle is inserted into cavity at the base of the spine, and the anaesthetic numbs nerves from the womb.

Side-effects

It is often offered as a method of achieving pain-free labour, although there can be side-effects, and studies suggest it increases the chance of doctors having to use a suction cap or forceps to deliver the child.

The research, by anaesthetists at North Staffordshire Hospital in Stoke on Trent, looked at 369 women, half of whom received an epidural, and the other half who got other forms of pain relief.

Too often, the epidural is presented simply as a way of having a pain-free delivery, an women are not informed of the downside

Belinda Phipps, National Childbirth Trust

They were then followed up to see who had back pain and given general checks of their spinal mobility.

The researchers found that there were no significant differences in mobility - or in pain reported by the women.

However, many experts believe that studies on this issue have so far involved too few women to yield a meaningful result.

Belinda Phipps, from the National Childbirth Trust, said she had encountered many women who could trace the root of their back pain to the epidural given during labour.

She told BBC News Online: "There's no such thing as a free lunch - as with every medical intervention, there is a price to pay.

"Too often, the epidural is presented simply as a way of having a pain-free delivery, and women are not informed of the downside."