According to the text, parturition is induced by a complex neuroendocrine mechanism involving signals that trigger the release of oxytocin from the maternal pituitary, which causes stronger uterine contractions. The summary also lists cortisol and estrogens as involved in this mechanism. In contrast, prolactin is explicitly stated to regulate the growth of mammary glands and the formation of milk (lactation), which occurs towards the end of pregnancy, rather than initiating parturition.