A pregnant woman tries breathing through labour pains.

Labour’s sharp pangs are softened for some women by a genetic variant that affects neurons in the womb. Credit: Getty

Neuroscience

A gene helps women in labour to skip the painkillers

Uncommon genetic variant dampens the response of uterine neurons that sense pain.

Giving birth can be a painful experience — but not for women with a rare DNA variant that reduces the ability of neurons to send pain signals to the brain.

Michael Lee at the University of Cambridge, UK, and his colleagues studied 72 women after they had given birth for the first time, including some who had not requested analgesics during labour. Such women tended to feel less pain when heat or pressure was applied to their arms than did those who had sought pain relief.

The researchers sequenced the new mothers’ DNA and found that there was a higher prevalence of a rare variant of KCNG4, a gene encoding a protein that helps to control the activation of neurons, in those who gave birth without pain relievers. Experiments on cells isolated from mice showed that the mutation reduces the sensitivity of the protein to electric signals. As a result, stronger contractions are needed to activate pain-sensing nerves in the uterus.

The finding could help to develop drugs to manage pain, the researchers say.