Hormonal control of parturition.

Birth relies on neural signals from the uterus and on maternal hormones that act on the uterus. In response to sensory neural input arising from the push of the fetus on the cervix, the maternal posterior pituitary gland releases oxytocin, which stimulates uterine smooth muscle contractions. The secretion of prostaglandins by the uterus also increases the strength of the contractions. Sensory receptors in the uterus detect the more forceful contractions and signal the mother's posterior pituitary gland to secrete more oxytocin, thus completing a positive feedback loop that further strengthens the contractions.