What stimulates milk production immediately after delivery?

Prolactin is the hormone that stimulates milk production immediately after delivery. It is secreted by the anterior pituitary gland and plays a crucial role in postpartum lactation. Following childbirth, levels of progesterone and estrogen, which had been elevated during pregnancy, drop significantly. This drop in progesterone, in particular, removes the inhibition on prolactin, allowing it to act on the lactating breast tissue to initiate milk production.

Immediately after delivery, the suckling of the infant at the breast also acts as a stimulus that further promotes the release of prolactin, reinforcing the milk supply as the demand increases. The physiological role of prolactin is fundamental during this early stage of breastfeeding, ensuring that the mother is capable of providing milk to her newborn.

While oxytocin is important for the let-down reflex, allowing the milk to be released, it is prolactin that is directly responsible for the synthesis of milk in the mammary glands. Estrogen and progesterone contribute to breast development during pregnancy but are not involved in stimulating milk production immediately after delivery.