Breastfeeding and Lactation

Lactation is the physiological production and secretion of milk by the breast, and breastfeeding is the feeding of an infant at the breast; together they are a central element of postpartum recovery and infant nutrition. The establishment, maintenance, and support of breastfeeding, along with its short- and long-term effects, are core topics of postpartum care.

Definition

Lactation is the hormonally regulated synthesis and secretion of milk by the mammary gland after birth, and breastfeeding is the practice of nourishing an infant with milk directly from the breast.

Scope

The topic covers the endocrine control of lactation, the stages of lactogenesis, the composition and benefits of human milk, common challenges to establishing breastfeeding, and the population-level evidence on breastfeeding's effects. It is framed as reference material and not as feeding instruction for an individual mother and infant.

Core questions

• How is lactation initiated and sustained hormonally?
• What are the stages of lactogenesis and milk composition?
• What short- and long-term effects are associated with breastfeeding at the population level?
• What factors support or impede the establishment of breastfeeding?

Key concepts

• Lactogenesis I and II
• Prolactin and milk synthesis
• Oxytocin and the milk-ejection (let-down) reflex
• Colostrum and mature milk
• Exclusive breastfeeding
• Latch and supply-demand regulation
• Lactational amenorrhea

Mechanisms

During pregnancy the breast is primed for milk production, and after delivery the fall in placental progesterone permits copious milk secretion (lactogenesis II). Suckling stimulates prolactin release, which drives milk synthesis, and oxytocin release, which contracts myoepithelial cells to eject milk (the let-down reflex). Continued milk removal sustains production through a supply-and-demand feedback loop, while the same suckling-driven endocrine state can suppress ovulation and produce lactational amenorrhea (aap-breastfeeding-2012; victora-2016).

Clinical relevance

Breastfeeding support is integrated into postpartum care because milk composition and feeding patterns are central to infant nutrition and because the lactation process intersects with maternal recovery and fertility. This entry summarizes the physiology and evidence as reference content and does not provide individualized feeding guidance.

Epidemiology

A major synthesis estimated the global prevalence of breastfeeding and reviewed its associations with infant and maternal health outcomes across high- and low-income settings, framing breastfeeding as having measurable population-level effects (victora-2016). Professional bodies summarize the evidence base supporting breastfeeding and recommend its support within maternity and postpartum care (aap-breastfeeding-2012; acog-2018-postpartum).

History

The scientific understanding of lactation as a prolactin- and oxytocin-driven process developed through twentieth-century endocrinology, and large epidemiologic syntheses in the twenty-first century reframed breastfeeding as a determinant of population health rather than solely an individual feeding choice (victora-2016).

Seminal works

• victora-2016
• aap-breastfeeding-2012

Frequently asked questions

What triggers milk production after birth?

Copious milk production (lactogenesis II) is triggered largely by the drop in placental progesterone after delivery, after which suckling-induced prolactin maintains synthesis and oxytocin drives the milk-ejection reflex.

What is colostrum?

Colostrum is the thick, nutrient- and antibody-rich first milk produced in the earliest days after birth, before the transition to mature milk; it is a defining feature of early lactation.