But only half of all adopting mothers who attempt to breastfeed will make any milk at all and few will produce enough to fully satisfy their babies. It's the suckling of a child that triggers milk production, not an automatic physiological reaction that begins during pregnancy.
Hormones drive the production of breast milk.
Prolactin, a hormone created by the pituitary gland, makes breast milk, and if you stimulate the breast enough to increase prolactin levels, you will get milk. They are totally separate bodily functions. Increases in the hormones estrogen and progesterone during pregnancy do help prepare a woman's body for breastfeeding by enlarging the ducts and alveoli, so it is more difficult to start the milk flowing in mothers who haven't delivered a child. Learn more about how your body makes breast milk . But don't expect to lactate overnight.