In human women, milk goes through different stages in order to meet the needs of their baby. As health professionals, it is important to understand the mechanics involved in its various processes to better support mothers and babies.
Common to all mammals, the fact remains that breast milk is a biological liquid unique to each species. In human women, milk goes through different stages in order to meet the needs of their baby. As health professionals, it is important to understand the mechanics involved in its various processes to better support mothers and babies.
The woman's breast has a special structure to allow vascular exchanges, milk production and expression.
This unique anatomy is not thus constituted at the time of birth, the woman will have to go through a series of changes during puberty and pregnancy in order to secrete breast milk that will satisfy the baby she is carrying both in quality and quantity. As you might have understood, not only does the woman's body go through many adaptive processes to respond to the needs of her developing baby, it also starts planning well before birth for the continuation of the maternal adventure via breastfeeding.
From the first weeks of pregnancy, hormones trigger a transformation in the cells of the breasts. Estrogens have the role of development of the galactophore ducts while progesterone allows a maturation of secretory and myoepithelial cells.
Many women suffer from breast tension during this process.
Thus, the breasts of the mother will be ready to respond to their nurturing function well before birth. Some visual external changes show how well this phenomenon of transformation unwinds:
Note that it is not necessary for an active discharge of colostrum to be reported to judge a good lactogenesis.
It is during the middle of the second trimester that the mammary glands will begin their secretory differentiation. This colostral phase is often referred to as stage I lactogenesis.
The first milk available for the baby is called colostrum. Viscous and rare, this milk can be enjoyed within a drop rather than a sip. Perfectly adapted to the newborn, it meets its most glaring need after birth, passive immunity.
The milk phase called lactogenesis II will be associated with abundant milk production during secretory activation. The drastic drop in progesterones, happening when the placenta has been fully expelled, causes a closure of the intercellular spaces at the lactocyte level. Milk comes in around days 2 to 5 postpartum, the fluid flows more easily and its volume grows rapidly, while other changes are reported such as tension, heat and heaviness of the breasts.
Different mechanisms are to be considered when it comes to evaluating and adjusting milk production in a mother. Fortunately, the female body once again has the essential tools to ensure this abundance in the first years of the baby’s life.
Under the effect of prolactin, lactocytes ensure the synthesis and variable storage of milk. Under the effect of oxytocin, the myoepithelial cells that surround the lactocytes contract and allow the milk to be ejected to the baby. This is called endocrine control of human lactation.
Autocrine control is also present within the secretory cells. The shape of the cells will vary depending on the volume of milk stored in the alveoli. The greater the expansion, the lesser milk production will be. Thus, the more baby drinks, the more the channels are "empty" and produce milk. This is the principle of supply and demand.
Prolactin, the main hormone that causes milk production and storage, is stimulated by the mechanical action of the baby's mouth against the receptors located on the areola and nipple. The greater the stimulation, the more abundant the milk will be. Note that other factors influence circulating prolactin levels, including the circadian cycle.
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Breastfeeding is a process that takes place in a perfectly normal way in at least 85% of postpartum women. Experience shows that with the right support from health professionals and the immediate entourage, at least 95% of women could exclusively breastfeed their child. As milk production evolves and adapts to the different stages of motherhood, the uniqueness of each woman must be considered. While it is true that human milk varies both in quantity and composition within the same day to perfectly meet the needs of the baby, the same goes for our advice which must also have a unique and adaptive character for each milk story.
Marie-Ève Brouillette, Perinatal Clinician Nurse for 10 years and Certified Lactation Consultant of the IBCLCE. Founder of private nursing perinatal services Sein-Biose. Certified as babywearing instructor and member of the INPE. Mother of 4 young kids.