A key genetic variant has been discovered in women who experience less pain during labour.
Researchers at the University of Cambridge found this 'natural epidural' to be attributed to a change in the KCNG4 gene, carried by one in 100 women. This offers insight into how childbirth pain is experienced and how it can be managed.
'Not only have we identified a genetic variant in a new player underlying different pain sensitivities,' said, senior co-author, Professor Frank Reimann, 'but we hope this can open avenues to the development of new drugs to manage pain.'
The team of scientists and clinicians, who published their results in Cell Reports, compared a group of women with uncomplicated vaginal deliveries who did not request pain relief during the delivery of their first child, to women who experienced similar births but were given analgesics. The women's heat, cold and pressure pain thresholds were measured by applying heat and pressure to their arms and plunging their hands into icy water. Consistently, the women who did not opt for pain relief showed higher tolerance to pain.
Next, the team analysed the women's genome and found the women with a higher pain threshold were more likely to have a variant in the KCNG4 gene.
KCNG4 provides instructions to make a protein which acts as a 'gate', controlling electrical signals that travel down our nerve cells carrying pain signals to the brain. Testing in mice confirmed the variant has a higher threshold to 'open the gate' and carry electrical signals to the brain, raising pain tolerance.
It is unknown whether men can carry this genetic variant as this research focused on pain during childbirth.
Although researchers acknowledged it is 'unusual' for women not to request pain relief during labour, each woman's experience is unique, and levels of pain can vary widely. Professor David Menon, a senior co-author, stresses the importance of identifying these differences: '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.'