MODEL RELEASED. Woman in early labour. Midwife checking a young woman in the early stages of labour (childbirth). The midwife is adjusting the ultrasound sensor of a cardiotocography (CTG) machine (centre left) which picks up the foetus' heartbeat. The machine also records uterine contractions. The foetus' heartbeats are closely monitored during childbirth in order to detect problems such as foetal distress, which occurs when the baby's oxygen supply is impaired. During early labour the contractions dilate the neck of the uterus (cervix) allowing the baby to leave the body.