Parturition is induced by a complex neuroendocrine mechanism. The signals for parturition originate from the fully developed foetus and the placenta which induce mild uterine contractions called foetal ejection reflex. This triggers release of oxytocin from the maternal pituitary. Estrogen and progesterone ratio increases, and prostaglandins are produced to stimulate uterine contractions. Prolactin is a hormone involved in milk production (lactation) and has no role in the initiation of parturition.