An ion channel, which controls uterine contractions during human labour and is dysregulated in obese women, has been identified in a study published in Nature Communications this week. The finding may explain why obese women often have irregular contractions and are more likely to require a caesarean section than non-obese women.

Successful vaginal delivery requires strong rhythmic contractions of the uterus which enable the baby’s head to dilate the cervix. However, the molecular underpinnings controlling these contractions are not well understood.

Helena Parkington and her team show that the potassium ion channel hERG is expressed in the human uterus. They find that hERG is active during pregnancy, where it suppresses contractions. At the onset of labour, however, hERG is turned off by an inhibitory protein. The release of this “brake”, mediated by hERG, then facilitates strong uterine contractions during labour. The team further demonstrates that the release of the brake is not working properly in obese women, providing a mechanistic explanation for why obese women tend to have poorer labour outcomes.