At the end of pregnancy, vigorous contraction of the uterus causes expulsion or delivery of the foetus. This process of delivery of the foetus (childbirth) is called parturition. Parturition is induced by a complex neuroendocrine mechanism. Oxytocin acts on the uterine muscle and causes stronger uterine contractions. The levels of estrogen and progesterone also increases. Prostaglandins act on myometrium and stimulates uterine contractions. Prolactin is a lactation hormone that has no role in initiation of parturition.