Lactation of suckling by the baby. The milk ejection reflex (also called let-down reflex) is not always consistent, especially at first. Once a woman is conditioned to nursing, let-down can be triggered by a variety of stimuli, including the sound of any baby. Even thinking about breastfeeding can stimulate this reflex, causing unwanted leakage, or both breasts may give out milk when an infant is feeding from one breast. However, this and other problems often settle after two weeks of feeding. Stress or anxiety can cause difficulties with breastfeeding. The release of the hormone oxytocin leads to the "milk ejection" or
Human milk microbiome genomes are uniquely equipped to metabolize HMOs, which are otherwise indigestible by enzymes of the infant gut, some have suggested a coevolutionary dynamic between HMOs and certain bacteria common in both the milk and infant gastrointestinal microbiomes. Furthermore, relative to other mammalian milks, primate milk, particularly human milk, appears to be unique with respect to the complexity and diversity of its oligosaccharide repertoire. Human milk is typified by greater overall HMO diversity and predominance of oligosaccharides known to promote growth of "Bifidobacterium" in the infant gut. Milk microbiota are thought to play an essential role in programming the infant immune