CPM Certified Professional Midwife

Answer: D - All of the above

Estrogen increases release of oxytocin from the pituitary gland. Estrogen also promotes the synthesis of the receptor for oxytocin in myometrium, and accelarates lysosomal disintegration in amnion cells (resulting in prostaglandin synthesis). Before onset of labor, the progesterone level falls (due to increased fetal production of DHEA - S). Prostaglandins are important factors which initiate and maintain labor.