One in 100 women feels less pain during childbirth thanks to a rare gene variant acting as anesthesia: Study
While childbirth can be harrowing for most women, some go through the experience with lesser discomfort. Now, researchers in their new study reveal that a rare version of a gene could be giving these women a higher pain tolerance. The gene called KCNG4 limits the flow of signals to the brain, thereby reducing pain. About one in 100 women carry this gene variant. The findings could make way for new pain relievers, researchers from the UK and Sweden said.
About 71% of pregnant women have opted for pain relievers — epidurals or other spinal anesthesia — to reduce labor pain, according to a study that gathered data between 2009 and 2014. It is a 10% jump from 2008, according to a previous study. Despite their widespread use, however, some women refused to take epidurals during childbirth.
“It is unusual for women to not request gas and air, or epidural for pain relief during labor, particularly when delivering for the first time,” Dr Michael Lee from the University of Cambridge and the joint first author, said in a statement. “When we tested these women, it was clear their pain threshold was generally much higher than it was for other women," he added.
In this study, Lee and his colleagues recruited 39 women who did not require painkillers during labor and 33 other women who needed them. The team gauged the participants' ability of pain tolerance through tests such as the application of heat and pressure to the arms and contact with icy water. Comparing the two groups, the team found that women who refused pain relievers during childbirth had higher pain thresholds for heat, cold, and mechanical pressure.
To check if genetic factors led to higher pain tolerance, the team gathered and analyzed DNA samples from both groups. While sequencing the samples, they found that KCNG4 was highly prevalent in women who did not require painkillers during labor. KCNG4 produces a defective protein. Under normal conditions, it acts as a gatekeeper for nerves that carry signals to alert the brain of the pain. But the altered version present in these women is not sensitive enough to open the gates, thereby limiting the flow of information. The defect fails to switch on the nerve cells that carry them.
"In fact, this defect acts as a natural epidural. It means it takes a much greater signal — in other words, stronger contractions during labor — to switch it on. This makes it less likely that pain signals can reach the brain," Dr St John Smith, co-author of the study, explained. “Not only have we identified a genetic variant in a new player underlying different pain sensitivities,” added senior co-author Professor Frank Reimann, “but we hope this can open avenues to the development of new drugs to manage pain.”
"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,” said Professor David Menon, senior co-author. The study was published in Cell Reports.