Final answer:
Breast milk composition changes during the first days of lactation with colostrum initially produced, helping the newborn's immune system and clearing bilirubin via meconium expulsion. During a single feeding, breastfeeding starts with foremilk that is rich in lactose and protein, and ends with hindmilk that is rich in fat.
Step-by-step explanation:
The subject of this question is the timing of the onset of jaundice in newborns as it relates to their feeding type, with an emphasis on the physiological effects of breast milk composition on bilirubin levels. During the first days of lactation, colostrum is produced, which is a thick, yellowish milk high in protein. Colostrum has special properties that enhance the newborn's immune defenses and help clear bilirubin by promoting the expulsion of meconium.
As lactation continues, the breast milk composition changes. The first milk at each feeding, known as foremilk, is watery and rich in lactose and protein, and it helps quench the infant's thirst. Later in the feeding, hindmilk, which is rich in fat, is secreted and helps satisfy the infant's hunger.
Breastfeeding helps clear bilirubin, the substance that can cause jaundice when present in high concentrations. Herein lies the significance: breastfed babies typically pass meconium, which helps clear bilirubin more effectively than in formula-fed babies, potentially leading to a decreased risk of jaundice or an earlier resolution of the condition.