Childbirth depends not only on hormones, but also on the ability of the uterus to perceive physical force. The researchers found that pressure and stretch sensors in the uterine muscles and surrounding nerves work together to trigger coordinated contractions. These sensors allow the uterus to sense pressure and tension during labor. When the sensors are disturbed, contractions weaken and labor slows down. This discovery explains the causes of stalled birth. It could lead to better birth control methods in the future. The uterus knows when to push thanks to these mechanical sensors.