Final answer:
The first breast milk produced after childbirth is colostrum, a nutrient-rich milk high in immunoglobulins essential for the newborn's early immunity. It transitions to mature milk around 10 days postpartum, with the composition changing even within a single feeding session.
Step-by-step explanation:
The first breast milk after childbirth is called colostrum. Colostrum is a special form of milk that mammals produce just after giving birth. It is a thick, yellowish substance high in proteins and immunoglobulins, vital for the newborn's immune defense, and contains less fat and glucose than mature breast milk. Colostrum is produced during the first 48-72 hours postpartum, and although only a small amount is produced, it's packed with nutrients essential for the newborn's first days of life. Following the secretion of colostrum, transitional milk comes in around the third postpartum day, which leads up to mature milk by approximately postpartum day 10.
The overall composition of breast milk changes during the early days of lactation, starting with colostrum and transitioning to mature milk. Within a single feeding session, the nature of the milk also changes; the initial foremilk is watery and quenches the infant's thirst, while the hindmilk that comes after is richer and satisfies the infant's hunger. This dynamic composition of breast milk ensures the infant receives a balance of hydration and nutrients required for healthy growth.