Introduction:
Lactation is a process of milk formation that begins in the mid-stage of pregnancy, even before the initial latch of the newborn takes place. A woman's breast tends to undergo various changes in composition, size, and shape during puberty, pregnancy, and lactation. All these stages are governed by a cascade of physiologic changes essential to successful breastfeeding in a woman’s body.
In the postpartum period, some women may experience breastfeeding difficulty if they have inadequate milk production, poor milk extraction, or insufficient caloric intake to meet their body demands. Therefore, all lactating mothers are recommended to have extra 300-500 calories per day to meet lactation needs. Besides, all women are suggested to frequently empty their breasts, usually every 2 hours to 3 hours, to maintain proper milk supply.
What Is Lactogenesis?
Lactogenesis is the onset of milk secretion from the mammary gland. It includes all the changes occurring in the mammary epithelium from undifferentiated mammary gland to fully developed lactation in a woman.
The release of prolactin hormones from the anterior pituitary gland and oxytocin from the posterior pituitary gland regulates milk secretion from the mammary gland. It is maintained by frequent removal of milk. Stimulation of the nipple by the suckling ability of the infant triggers the release of these hormones. The mammary gland must receive hormonal signals to maintain milk secretion. Although these hormones act independently, their collective action is essential for successful breastfeeding.
There is a change in concentration and milk volume from colostrum to transitional milk and mature milk. Therefore, it varies according to the growing needs of the infants. That is why breast milk is considered the best source of nutrition for infants' growth and development. All breastfeeding mothers are suggested to breastfeed their newborn as often as possible to maintain a proper flow of milk supply in the mammary ducts.
What Is the Physiology of Lactation?
Women's breasts are composed of two major structures called ducts and lobules. Approximately ten major ducts open onto the skin surface of the nipple. Large ducts lead to the terminal duct lobular unit, and these terminal ducts branch into grape-like clusters of small acini to form a lobule. There are mainly three types of lobules:
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Type 1.
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Type 2.
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Type 3.
These lobules are formed at different stages of a woman's development. These lobules increase progressively in number and size by the end of pregnancy. The breast is composed entirely of lobules separated by small amounts of the stroma at this stage.
During puberty, the formation of lobule type 1 occurs. The level of estrogen and progesterone during each menstrual cycle stimulates lobule 1 to produce new alveolar buds. This leads to the formation of type-2 and type-3 lobules in the breasts. After the completion of puberty, there occurs no further change in the female breast until pregnancy.
What Are the Stages of Lactogenesis?
Lactogenesis is the process of developing the ability to secrete breast milk. The method of lactation involves the maturation of alveolar cells. There are mainly two stages: secretory initiation and secretory activation.
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Stage I Lactogenesis: It is secretory initiation during the mid-stage of pregnancy. During that period, the placenta supplies more progesterone which inhibits further differentiation. As a result, some women may notice small amounts of milk secretion by a week 16th of gestation, and some may express colostrum by late pregnancy.
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Stage II Lactogenesis: It is secretory activation that begins with copious milk formation after delivery. It is stimulated by removing the placenta at delivery, the rapid drop in progesterone levels, and elevated prolactin, cortisol, and insulin levels. It is commonly reported that most women experience swelling of the breast and copious milk production on the second or third day of postpartum. Some reports claim lower milk volume in women who had cesarean births than those who delivered vaginally. The women with placental remnants, diabetes, and stressful vaginal deliveries show a late onset of milk production. The retained placental fragments could inhibit lactogenesis stage II by continued secretion of progesterone that remains the same until removing the remaining placental fragments.
The secretion of prolactin hormone increases rapidly with the suckling of the nipple by the infant, as it stimulates the nerve endings located around the nipples. Oxytocin is responsible for milk ejection or letdown reflex. It leads to the contraction of cells, hence forcing milk into the mammary ducts that come out through the nipple. Additionally, oxytocin has a psychological effect, and it can induce a calm state to reduce stress. Ultimately, it helps to enhance the feelings of affection between the mother and the child, which is essential for their bonding.
After establishing lactation, production is regulated by the interaction of physical and biochemical factors. For example, when breast milk is not removed, an elevation in the intramammary pressure causes the accumulation of a feedback inhibitor of lactation to reduce the milk production and initiate mammary involution.
However, if breast milk is adequately removed from the breast, the inhibitor is also removed, and the secretion of breast milk will continue normally. The feedback inhibitor of lactation regulates the milk volume, which is primarily determined by how much milk the baby takes.
Conclusion:
Lactogenesis stage I starts when you are six months pregnant. Some may experience milk secretion from their breast by the end of pregnancy. Lactogenesis stage II is the onset of the secretion of copious breast milk called colostrum. It occurs during the first four days of postpartum. Colostrum has various health benefits for infants. It provides a protective shield for newborns and prevents many systemic diseases in the later stages of life. Sometimes delayed lactogenesis can occur with stressful deliveries or in the case of an underlying systemic disease like diabetes. You may seek the help of a lactation specialist if the milk formation is delayed for an extended period.
