**2.2 Endocrinology of labor**

Hormonal signals play a crucial role in orchestrating the initiation and progression of labor. Throughout pregnancy, progesterone keeps the uterus in a quiescent state [1, 9, 10]. As labor approaches, progesterone levels decline, while estrogen and corticotropin-releasing hormone (CRH) start to rise [9]. CRH is released from the placenta and stimulates the fetal adrenal glands to produce cortisol which in turn boosts the production of prostaglandins [9]. Estrogen also promotes the synthesis of prostaglandins, increases receptivity to oxytocin, and stimulates the growth of uterine muscle, leading to the initiation of labor [9]. Prostaglandins help soften and ripen the cervix [1, 10]. During this time, oxytocin levels and receptors rise, aiding in the stimulation of the smooth muscle fibers in the myometrium leading to an increase in the frequency, duration, and intensity of uterine contractions [9, 10]. Oxytocin is released from the posterior pituitary gland, and its release is regulated by a positive feedback mechanism during labor, where further descent of the fetus into the pelvis increases oxytocin release [6].
