Final answer:
The composition of breast milk changes from colostrum high in immunoglobulins in the first 2-3 days after birth to transitional milk, and then to mature milk by the tenth day. Foremilk and hindmilk within a single feeding meet the immediate hydration and nutritional needs of the infant respectively.
Step-by-step explanation:
During the initial days of lactation, the composition of breast milk undergoes significant changes to meet the nutritional and immunological needs of the newborn. Colostrum is secreted during the first 48-72 hours postpartum. Although only produced in small volumes, approximately 3 ounces in a 24-hour period, it plays a crucial role in providing immunoglobulins which help in gastrointestinal and systemic immunity for the newborn's adjustment to the nonsterile environment.
Following the colostrum phase, transitional milk is produced starting from the third postpartum day. This type of milk serves as an intermediate stage before the secretion of mature breast milk, which generally begins around the tenth day postpartum. Foremilk, the initial milk during a feeding, is designed to quench the infant’s thirst. As feeding continues, hindmilk is released, richer in fat content, to satisfy the infant's hunger.
It is also essential to highlight that breastfeeding plays a vital role in helping the newborn's digestive system to expel meconium and clear bilirubin, assisting in overall neonatal adjustment and development.