Follicle stimulating hormone (FSH) and luteinizing hormone work in collaboration with each other to stimulate the follicles within the female reproductive system to release an egg. This is known as ovulation. When the eggs meets sperm, the human gonadotrophin (hCG) hormone is released to trigger elevated levels of estrogen and progesterone. Estrogen and progesterone are the two key pregnancy hormones. Estrogen is instrumental in promoting uterine growth, regulating other pregnancy hormones, and promoting the development of the embryo's organs. The placenta produces placental growth factor and human placental lactogen (HPL) hormones to increase the blood volume and adjust the metabolism of the mother to help nourish the fetus. Progesterone encourages the growth of breast tissue in preparation for breastfeeding after birth. Relaxin works in collaboration with progesterone to relax the mother's joints and ligaments in preparation for labor and childbirth.

Prolactin is a hormone that is responsible for breastmilk production and the regulation of breastmilk. During pregnancy and breastfeeding, prolactin levels are elevated in order to increase insulin resistance, regulate lipid metabolism, and increase growth factor levels. Once a baby is born, oxytocin is responsible for the muscle contractions in the alveoli of the breasts in order to squeeze milk into the milk ducts of the breasts. Oxytocin also causes the "milk let down" that results when a baby breastfeeds.