Foetal ejection reflex in human female is induced by

Oxytocin (child birth hormone) secreted by neurohypophysis of pituitary gland stimulates contraction of uterius muscles, including labour pain for child birth, when secretion of progesterone hormone declines, making the end of pregnancy. As the sensory impulse of increasing labour pain reaches hypothalamus, more and more oxytocin is released from posterior pituitary under a positive feedback regulation childbirth, it dilates the cervix (vaginal stretching).