Answer:
Oxytocin
Step-by-step explanation:
Positive feedback mechanism is the one by which the changes leads to more changes of same type.
During child birth, the head of the baby is pressed against the cervix which in turn send the nerve impulses to brain. Brain makes the pituitary gland to secrete the hormone oxytocin. Oxytocin is released in blood and causes the uterine contraction. As labor continues, more stimulation of cervix and intense uterine contractions lead to more release of oxytocin.