The correct option is D A-cortisol B-placenta C- vigorous contractions of uterus
Parturition or child birth is the act of bringing forth an infant from the uterus. In the event of parturition, some of the fetal cells (hypothalamic-pituitary adrenal axis) produces cortisol which acts on the placenta to stimulate the conversion of pregnenolone to estrogen. As a result, the normal progesterone to estrogen ratio is altered in the pregnant female. This disturbance leads to production of prostaglandins which are critical to the myometrial contractions leading to labour. Thus, the correct answer is D.