Mothers with rare gene feel less pain while giving birth

Around 1pc of women have variant that acts as a ‘natural epidural’ during labour, study discovers

ONE in 100 women carry a gene that raises their pain threshold, allowing them to give birth without anaesthetic, a study has found.

The rare genetic variant, known as KCNG4, acts as a “natural epidural”, inhibiting pain signals to the brain during contractions.

Scientists from the University of Cambridge compared 33 women who were delivering their first child and did not request any pain relief during an uncomplicated vaginal delivery with a control group of 33 women who were given pain relief during delivery of their firstborn.

Two women in the first group carried KCNG4, a much higher proportion than average.

Researchers carried out three tolerance tests on each of the women for cold, heat and mechanical pressure. The tests involved submerging their hands in icy water, attaching hot thermode to their forearm and contracting a cuff on their upper arm.

The first group of women, containing the KCNG4 gene carriers, were found to have a greater ability to withstand pain, which could account for why they did not request pain relief during childbirth.

Dr Michael Lee, from Cambridge university’s Division of Anaesthesia, said: “It is unusual for women to not request gas and air, or epidural for pain relief during labour, particularly when delivering for the first time.

“When we tested these women, it was clear their pain threshold was generally much higher than it was for other women.”

There is therefore a higher degree of pain tolerance in a group of women among whom KCNG4 carriers are over-represented, the study suggested.

KCNG4 inhibits the ability of nerve cells to send signals to the brain, where the sensation of pain is registered.

Dr Ewan St John Smith, senior co-author, said: “The genetic variant that we found in women who feel less pain during childbirth leads to a ‘defect’ in the formation of the switch on the nerve cells.

“In fact, this defect acts like a natural epidural. It means it takes a much greater signal – in other words, stronger contractions during labour – to switch it on. This makes it less likely that pain signals can reach the brain.”

It is hoped that the study, published in the peer-reviewed journal Cell

Reports, will aid the development of new drugs to help control labour pain.

Professor Frank Reimann, co-author of the study, said: “Not only have we identified a genetic variant in a new player underlying different pain sensitivities, but we hope this can open avenues to the development of new drugs to manage pain.”

Scientists also believe the discovery could lead to better treatments for other types of pain.

Professor David Menon, senior coauthor, said: “This approach of studying individuals who show unexpected extremes of pain experience also may find wider application in other contexts, helping us understand how we experience pain and develop new drugs to treat it.”