Final answer:
Breast milk composition changes after childbirth from high-protein colostrum to transitional milk, and then to mature milk by the tenth day. Mature milk itself varies during a feed, starting with lactose and protein-rich foremilk, followed by fat-rich hindmilk.
Step-by-step explanation:
The composition of breast milk varies through different stages of lactation and even during a single feeding session. At the onset of lactation following childbirth, the mother produces colostrum, which is high in protein but lower in fat and glucose when compared to mature milk. After about three postpartum days, transitional milk is secreted, which is an intermediate between colostrum and mature milk, becoming mature milk around the tenth postpartum day.
Mature breast milk further changes during a feeding. The early milk or foremilk is watery, rich in lactose and protein, and quenches the infant's thirst. As the feeding progresses, hindmilk is delivered which is creamier, high in fat, and satisfies the infant's hunger. This adaptive mechanism ensures the infant receives a balanced intake of nutrients tailored to its immediate needs.