Lactation describes the secretion of milk from the mammary glands and the period of time that a mother lactates to feed her young. The process can occur with all post-pregnancy female mammals, although it predates mammals. In humans the process of feeding milk is also called breastfeeding or nursing. Newborn infants often produce some milk from their own breast tissue, known colloquially as witch's milk.
In most species, milk comes out of the mother's nipples; however, the monotremes, egg-laying mammals, lack nipples and release milk through ducts in the abdomen. In only one species of mammal, the Dayak fruit bat, is milk production a normal male function.
Galactopoiesis is the maintenance of milk production. This stage requires prolactin. Oxytocin is critical for the milk let-down reflex in response to suckling. Galactorrhea is milk production unrelated to nursing. It can occur in males and females of many mammal species as result of hormonal imbalances such as hyperprolactinaemia.
The chief function of a lactation is to provide nutrition and immune protection to the young after birth. In almost all mammals, lactation induces a period of infertility (in humans, lactational amenorrhea), which serves to provide the optimal birth spacing for survival of the offspring.
It is also possible to induce lactation without pregnancy. Protocols for inducing lactation are called the Goldfarb protocols. Using birth control pills to mimic the hormone levels of pregnancy, then discontinuing the birth control, followed by use of a double electric breast pump for 15 minute sessions at regular 2-3 hour intervals (100+ minutes total per day)_ helps induce milk production.
During the latter part of pregnancy, the woman's breasts enter into the Secretory Differentiation stage. This is when the breasts make colostrum (see below), a thick, sometimes yellowish fluid. At this stage, high levels of progesterone inhibit most milk production. It is not a medical concern if a pregnant woman leaks any colostrum before her baby's birth, nor is it an indication of future milk production.
At birth, prolactin levels remain high, while the delivery of the placenta results in a sudden drop in progesterone, estrogen, and HPL levels. This abrupt withdrawal of progesterone in the presence of high prolactin levels stimulates the copious milk production of Secretory Activation.
When the breast is stimulated, prolactin levels in the blood rise, peak in about 45 minutes, and return to the pre-breastfeeding state about three hours later. The release of prolactin triggers the cells in the alveoli to make milk. Prolactin also transfers to the breast milk. Some research indicates that prolactin in milk is greater at times of higher milk production, and lower when breasts are fuller, and that the highest levels tend to occur between 2 a.m. and 6 a.m.
Other hormones—notably insulin, thyroxine, and cortisol—are also involved, but their roles are not yet well understood. Although biochemical markers indicate that Secretory Activation begins about 30–40 hours after birth, mothers do not typically begin feeling increased breast fullness (the sensation of milk "coming in the breast") until 50–73 hours (2–3 days) after birth.
Colostrum is the first milk a breastfed baby receives. It contains higher amounts of white blood cells and antibodies than mature milk, and is especially high in immunoglobulin A (IgA), which coats the lining of the baby's immature intestines, and helps to prevent pathogens from invading the baby's system. Secretory IgA also helps prevent food allergies. Over the first two weeks after the birth, colostrum production slowly gives way to mature breast milk.
The hormonal endocrine control system drives milk production during pregnancy and the first few days after the birth. When the milk supply is more firmly established, autocrine (or local) control system begins.
During this stage, the more that milk is removed from the breasts, the more the breast will produce milk. Research also suggests that draining the breasts more fully also increases the rate of milk production. Thus the milk supply is strongly influenced by how often the baby feeds and how well it is able to transfer milk from the breast. Low supply can often be traced to:
This is the mechanism by which milk is transported from the breast alveoli to the nipple. Suckling by the baby stimulates the paraventricular nuclei and supraoptic nucleus in the hypothalamus, which signals to the posterior pituitary gland to produce oxytocin. Oxytocin stimulates contraction of the myoepithelial cells surrounding the alveoli, which already hold milk. The increased pressure causes milk to flow through the duct system and be released through the nipple. This response can be conditioned e.g. to the cry of the baby.
Milk ejection is initiated in the mother's breast by the act 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 let-down reflex. Oxytocin stimulates the muscles surrounding the breast to squeeze out the milk. Breastfeeding mothers describe the sensation differently. Some feel a slight tingling, others feel immense amounts of pressure or slight pain/discomfort, and still others do not feel anything different.
A poor milk ejection reflex can be due to sore or cracked nipples, separation from the infant, a history of breast surgery, or tissue damage from prior breast trauma. If a mother has trouble breastfeeding, different methods of assisting the milk ejection reflex may help. These include feeding in a familiar and comfortable location, massage of the breast or back, or warming the breast with a cloth or shower.
This is the mechanism by which milk is transported from the breast alveoli to the nipple. Suckling by the baby innervates slowly-adapting and rapidly-adapting mechanoreceptors that are densely packed around the areolar region. The electrical impulse follows the spinothalamic tract, which begins by innervation of fourth intercostal nerves. The electrical impulse then ascends the posterolateral tract for one or two vertebral levels and synapses with second-order neurons, called tract cells, in the posterior dorsal horn. The tract cells then decussate via the anterior white commissure to the anterolateral corner and ascend to the supraoptic nucleus and paraventricular nucleus in the hypothalamus, where they synapse with oxytocinergic third-order neurons. The somas of these neurons are located in the hypothalamus, but their axon and axon terminals are located in the infundibulum and pars nervosa of the posterior pituitary, respectively. The oxytocin is produced in the neuron's soma in the supraoptic and paraventricular nuclei, and is then transported down the infundibulum via the hypothalamo-neurohypophyseal tract with the help of the carrier protein, neurophysin I, to the pars nervosa of the posterior pituitary, and then stored in Herring bodies, where they are stored until the synapse between second- and third-order neurons.
Following the electrical impulse, oxytocin is released into the bloodstream. Through the bloodstream, oxytocin makes its way to myoepithelial cells, which lie between the extracellular matrix and luminal epithelial cells that also make up the alveoli in breast tissue. When oxytocin binds to the myoepithelial cells, the cells contract. The increased intra-aveolar pressure forces milk into the lactiferous sinuses, into the lactiferous ducts (a study found that lactiferous sinuses may not exist. If this is true then milk simply enters the lactiferous ducts), and then out the nipple.
A surge of oxytocin also causes the uterus to contract. During breastfeeding, mothers may feel these contractions as afterpains. These may range from period-like cramps to strong labour-like contractions and can be more severe with second and subsequent babies. 
In humans, induced lactation and relactation have been observed frequently in some cultures, and demonstrated with varying success in adoptive mothers. It appears plausible that the possibility of lactation in women (or females of other species) who are not biological mothers does confer an evolutionary advantage, especially in groups with high maternal mortality and tight social bonds. The phenomenon has been also observed in most primates, in some lemurs, and in dwarf mongooses.
Lactation can be induced in humans by a combination of physical and psychological stimulation, by drugs, or by a combination of those methods. Some couples may stimulate lactation outside of pregnancy for sexual purposes.
Rare accounts of male lactation (as distinct from galactorrhea) exist in historical medical and anthropological literature, although the phenomenon has not been confirmed by more recent literature.
Charles Darwin recognized that mammary glands seemed to have developed specifically from cutaneous glands, and hypothesized that they evolved from glands in brood pouches of fish, where they would provide nourishment for eggs. The latter aspect of his hypothesis has not been confirmed; however, more recently the same mechanism has been postulated for early synapsids.
As all mammals lactate, lactation must have evolved before the last common ancestor of all mammals, which places it at a minimum in the Middle or Late Triassic when monotremes diverged from therians. O. T. Oftedal has argued that therapsids evolved a proto-lacteal fluid in order to keep eggs moist, an adaption necessitated due to diapsids parchment shelled eggs which are more vulnerable to evaporation and dehydration than the mineralized eggs produced by some sauropsids. This protolacteal fluid became a complex, nutrient-rich milk which then allowed a decline in egg size by reducing the dependence on a large yolk in the egg. The evolution of lactation is also believed to have resulted in the more complex dentition seen in mammals, as lactation would have allowed the prolonged development of the jaw before the eruption of teeth.
During early evolution of lactation, the secretion of milk was through pilosebaceous glands on mammary patches, analogous to the areola, and hairs on this patch transported the nourishing fluids to the hatchlings as is seen in monotremes. Later the development of the nipple rendered mammary hairs obsolete.
Another well known example of nourishing young with secretions of glands is the crop milk of columbiform birds. Like in mammals, this also appears to be directed by prolactin. Other birds such as flamingos and penguins utilize similar feeding techniques.
The discus fish (Symphysodon) is known for (biparentally) feeding their offspring by epidermal mucus secretion. A closer examination reveals that, as in mammals and birds, the secretion of this nourishing fluid may be controlled by prolactin. Similar behavior is seen in at least 30 species of cichlids.
Lactation is also the hallmark of adenotrophic viviparity - a breeding mechanism developed by some insects, most notably tsetse flies. The single egg of the tsetse develops into a larva inside the uterus where it is fed by a milky substance secreted by a milk gland inside the uterus. The cockroach species Diploptera punctata is also known to feed their offspring by milky secretions.
Toxeus magnus, an ant-mimicking jumping spider species of Southeast Asia, also lactates. It nurses its offspring for about 38 days, although they are able to forage on their own after 21 days. Blocking nursing immediately after birth resulted in complete mortality of the offspring, whereas blocking it 20 days after birth resulted in increased foraging and reduced survival. This form of lactation may have evolved from production of trophic eggs.
The human areola (areola mammae, or ) is the pigmented area on the breast around the nipple. Areola, more generally, is a small circular area on the body with a different histology from the surrounding tissue, or other small circular areas such as an inflamed region of skin.
The mature human female nipple has several small openings arranged radially around the tip of the nipple (lactiferous ducts) from which milk is released during lactation. Other small openings in the areola are sebaceous glands, known as Montgomery's glands.Breastfeeding
Breastfeeding, also known as nursing, is the feeding of babies and young children with milk from a woman's breast. Health professionals recommend that breastfeeding begin within the first hour of a baby's life and continue as often and as much as the baby wants. During the first few weeks of life babies may nurse roughly every two to three hours and the duration of a feeding is usually ten to fifteen minutes on each breast. Older children feed less often. Mothers may pump milk so that it can be used later when breastfeeding is not possible. Breastfeeding has a number of benefits to both mother and baby, which infant formula lacks.Deaths of an estimated 820,000 children under the age of five could be prevented globally every year with increased breastfeeding. Breastfeeding decreases the risk of respiratory tract infections and diarrhea, both in developing and developed countries. Other benefits include lower risks of asthma, food allergies, type 1 diabetes, and leukemia. Breastfeeding may also improve cognitive development and decrease the risk of obesity in adulthood. Mothers may feel pressure to breastfeed, but in the developed world children generally grow up normally when bottle fed.Benefits for the mother include less blood loss following delivery, better uterus shrinkage, and decreased postpartum depression. Breastfeeding delays the return of menstruation and fertility, a phenomenon known as lactational amenorrhea. Long term benefits for the mother include decreased risk of breast cancer, cardiovascular disease, and rheumatoid arthritis. Breastfeeding is less expensive than infant formula.Health organizations, including the World Health Organization (WHO), recommend breastfeeding exclusively for six months. This means that no other foods or drinks other than possibly vitamin D are typically given. After the introduction of foods at six months of age, recommendations include continued breastfeeding until one to two years of age or more. Globally about 38% of infants are only breastfed during their first six months of life. In the United States in 2015, 83% of women begin breastfeeding and 58% were still breastfeeding at 6 months, although only 25% exclusively. Medical conditions that do not allow breastfeeding are rare. Mothers who take certain recreational drugs and medications should not breastfeed. Smoking, limited amounts of alcohol, or coffee are not reasons to avoid breastfeeding.Breastfeeding difficulties
Breastfeeding difficulties refers to problems that arise from breastfeeding, the feeding of an infant or young child with milk from a woman's breasts. Although babies have a sucking reflex that enables them to suck and swallow milk, and although human breast milk is usually the best source of nourishment for human infants, there are circumstances under which breastfeeding can be problematic, or even, in rare instances, contraindicated.
Difficulties can arise both in connection with the act of breastfeeding and with the health of the nursing infant.Diana West (lactation consultant)
Diana West is a leading lactation consultant and author specializing on the topic of breastfeeding.Domperidone
Domperidone, sold under the brand name Motilium among others, is a peripherally selective dopamine D2 receptor antagonist that was developed by Janssen Pharmaceutica and is used as an antiemetic, gastroprokinetic agent, and galactagogue. It may be administered orally or rectally, and is available in the form of tablets, orally disintegrating tablets (based on Zydis technology), suspension, and suppositories. The drug is used to relieve nausea and vomiting; to increase the transit of food through the stomach (by increasing gastrointestinal peristalsis); and to promote lactation (breast milk production) by release of prolactin.Erotic lactation
Erotic lactation is sexual arousal by breastfeeding on a woman's breast. Depending on the context, the practice can also be referred to as adult suckling, adult nursing, and adult breastfeeding. Practitioners sometimes refer to themselves as being in an adult nursing relationship (ANR). Two persons in an exclusive relationship can be called a nursing couple.
"Milk fetishism" and "lactophilia" are medical, diagnostic terms for paraphilias and are used for disorders according to the precise criteria of ICD-10 and DSM-IV.Galactocele
A galactocele (also called lacteal cyst or milk cyst) is a retention cyst containing milk or a milky substance that is usually located in the mammary glands. They can occur in women during or shortly after lactation.
They present as a firm mass, often subareolar, and are caused by the obstruction of a lactiferous duct. Clinically, they appear similar to a cyst on examination. The duct becomes more distended over time by epithelial cells and milk. It may rarely be complicated by a secondary infection and result in abscess formation. These cysts may rupture leading to formation of inflammatory reaction and may mimic malignancy.
Once lactation has ended the cyst should resolve on its own without intervention. A galactocele is not normally infected as the milk within is sterile and has no outlet through which to become contaminated. Treatment is by aspiration of the contents or by excision of the cyst. Antibiotics are given to prevent infection.Galactoceles may be associated with oral contraceptive use.Lactation consultant
A lactation consultant is a health professional who specializes in the clinical management of breastfeeding. The International Board of Lactation Consultant Examiners (IBLCE) certifies lactation consultants who meet its criteria and have passed its exam.Lactation room
Lactation room (or Lactorium) is an American English term for a private space where a nursing mother can use a breast pump. The development is mostly confined to the United States, which is unique among developed countries in providing minimal maternity leave. Historian Jill Lepore argues that the "non-bathroom lactation room" and breast pumps generally are driven by corporate need for workers rather than mothers' wishes or babies' needs.Lactation suppression
Lactation suppression refers to the act of suppressing lactation by medication or other non pharmaceutical means. The breasts may become painful when engorged with milk if breastfeeding is ceased abruptly, or if never started. This may occur if a woman never initiates breastfeeding, or if she is weaning from breastfeeding abruptly. Historically women who did not plan to breastfeed were given diethylstilbestrol and other medications after birth to suppress lactation. However, its use was discontinued, and there are no medications currently approved for lactation suppression in the US and the UK.Lactivism
Lactivism (a portmanteau of "lactation" and "activism") is the doctrine or practice of vigorous action or involvement as a means of achieving a breastfeeding culture, sometimes by demonstrations, protests, etc. of breastfeeding. Supporters, referred to as "lactivists", seek to protest the violation of International Code of Marketing of Breast-milk Substitutes by formula companies and industry.
One form that lactivism takes is the staging of a "nurse-in" (a play on "sit-in"), which involves women gathering in public to nurse their children, usually to protest incidents in which a nursing mother was asked to cover up or leave a location because she was nursing.During nurse-ins, nursing mothers often wear clothing with the International Breastfeeding Symbol on it, to show their solidarity.Another form of lactivism is acting as support for mothers that wish to nurse. Lactivists provide information and share resources on successful nursing.
Many lactivists choose to breastfeed their children over bottle feeding, seeing this as the natural way to provide nutrition. It is claimed that breastfeeding provides a bonding experience superior to that or bottle feeding. Lactivists may also argue that bottle feeding is costlier than breastfeeding as it requires a multitude of items, and the money saved from breastfeeding can be spent on other useful items for the child. Multiple health organizations recommend breast milk as the primary source of nutrition for babies, including the American Academy of Pediatrics, the American Medical Association, and the World Health Organization.Lactose synthase
Lactose synthase is an enzyme that generates lactose from glucose and UDP-galactose.
It is classified under EC 220.127.116.11.
It consists of N-acetyllactosamine synthase and alpha-lactalbumin. Alpha-lactalbumin, which is expressed in response to prolactin, increases the affinity of N-acetyllactosamine synthase for its substrate, causing increased production of lactose during lactation.Low milk supply
In breastfeeding women, low milk supply, also known as lactation insufficiency, insufficient milk syndrome, agalactia, agalactorrhea, hypogalactia or hypogalactorrhea, is the production of breast milk in daily volumes that do not fully meet the nutritional needs of her infant.
Breast milk supply augments in response to the baby's demand for milk, and decreases when milk is allowed to remain in the breasts. Low milk supply is usually caused by allowing milk to remain in the breasts for long periods of time, or insufficiently draining the breasts during feeds. It is usually preventable, unless caused by medical conditions that have been estimated to affect up to five percent of women.Several common misconceptions often lead mothers to believe they have insufficient milk when they are in fact producing enough. Actual low milk supply is likely if the baby is latching and swallowing well at the breast, is nevertheless not growing well or is showing signs of dehydration or malnutrition, and does not have a medical condition that would explain the lack of growth. The main method for increasing milk supply is improved breastfeeding practices and/or expressing milk through pumping or hand expression. The medication domperidone increases milk supply for some women. For mothers who cannot breastfeed exclusively, breastfeeding as much as possible, with supplementary formula feeding as necessary, offers many benefits over formula alone.Male lactation
In zoology, male lactation is production of milk (lactation) from a male mammal's mammary glands. It is well-documented in the Dayak fruit bat. The term male lactation is not used in human medicine. It has been used in popular literature, such as Louise Erdrich's The Antelope Wife, to describe the phenomenon of male galactorrhea, which is a well-documented condition in humans, unrelated to childbirth or nursing. Newborn babies of both sexes can occasionally produce milk; this is called neonatal milk (also known as "witch's milk") and not considered male lactation.Mammary gland
A mammary gland is an exocrine gland in mammals that produces milk to feed young offspring. Mammals get their name from the Latin word mamma, "breast". The mammary glands are arranged in organs such as the breasts in primates (for example, humans and chimpanzees), the udder in ruminants (for example, cows, goats, and deer), and the dugs of other animals (for example, dogs and cats). Lactorrhea, the occasional production of milk by the glands, can occur in any mammal, but in most mammals, lactation, the production of enough milk for nursing, occurs only in phenotypic females who have gestated in recent months or years. It is directed by hormonal guidance from sex steroids. In a few mammalian species, including humans, male lactation can occur.Milk
Milk is a nutrient-rich, white liquid food produced by the mammary glands of mammals. It is the primary source of nutrition for infant mammals (including humans who are breastfed) before they are able to digest other types of food. Early-lactation milk contains colostrum, which carries the mother's antibodies to its young and can reduce the risk of many diseases. It contains many other nutrients including protein and lactose. Interspecies consumption of milk is not uncommon, particularly among humans, many of whom consume the milk of other mammals.As an agricultural product, milk, also called dairy milk, is extracted from farm animals during or soon after pregnancy. Dairy farms produced about 730 million tonnes of milk in 2011, from 260 million dairy cows. India is the world's largest producer of milk, and is the leading exporter of skimmed milk powder, yet it exports few other milk products. The ever increasing rise in domestic demand for dairy products and a large demand-supply gap could lead to India being a net importer of dairy products in the future. The United States, India, China and Brazil are the world's largest exporters of milk and milk products. China and Russia were the world's largest importers of milk and milk products until 2016 when both countries became self-sufficient, contributing to a worldwide glut of milk.Throughout the world, more than six billion people consume milk and milk products. Over 750 million people live in dairy farming households.Nursing Madonna
The Nursing Madonna, Virgo Lactans, or Madonna Lactans, is an iconography of the Madonna and Child in which the Virgin Mary is shown breastfeeding the infant Jesus.
The depiction is mentioned by Pope Gregory the Great, and a mosaic depiction probably of the 12th century is on the facade of Santa Maria in Trastevere in Rome, though few other examples survive from before the late Middle Ages. It continued to be found in Orthodox icons (as Galaktotrophousa in Greek, Mlekopitatelnitsa in Russian), especially in Russia.Usage of the depiction seems to have revived with the Cistercian Order in the 12th century, as part of the general upsurge in Marian theology and devotion. Milk was seen as "processed blood", and the milk of the Virgin to some extent paralleled the role of the Blood of Christ.In the Middle Ages, the middle and upper classes usually contracted breastfeeding out to wetnurses, and the depiction of the Nursing Madonna was linked with the Madonna of Humility, a depiction that showed the Virgin in more ordinary clothes than the royal robes shown, for instance, in images of the Coronation of the Virgin, and often seated on the ground. The appearance of a large number of such depictions in Tuscany in the early 14th century was something of a visual revolution for the theology of the time, compared to the Queen of Heaven depictions; they were also popular in Iberia. After the Council of Trent in the mid-16th century, clerical writers discouraged nudity in religious subjects, and the use of the Madonna Lactans iconography began to fade away.Another type of depiction, also deprecated after Trent, showed Mary baring her breast in a traditional gesture of female supplication to Christ when asking for mercy for sinners in Deesis or Last Judgement scenes. A good example is the fresco at S. Agostino in San Gimignano, by Benozzo Gozzoli, painted to celebrate the end of the plague.The nursing Virgin survived into the Baroque some depictions of the Holy Family, by El Greco for example, and narrative scenes such as the Rest on the Flight into Egypt, for example by Orazio Gentileschi (versions in Birmingham and Vienna).Postpartum physiological changes
The postpartum physiological changes are those expected changes that occur to the woman's body after childbirth, in the postpartum period. These changes mark the beginning of the return of pre-pregnancy physiology and of breastfeeding. Most of the time these postnatal changes are normal and can be managed with medication and comfort measures, but in a few situations complications may develop. Postpartum physiological changes may be different for women delivering by cesarean section. Other postpartum changes, may indicate developing complications such as, postpartum bleeding, engorged breasts, postpartum infections.Pregnancy category
The pregnancy category of a medication is an assessment of the risk of fetal injury due to the pharmaceutical, if it is used as directed by the mother during pregnancy. It does not include any risks conferred by pharmaceutical agents or their metabolites in breast milk.
Every drug has specific information listed in its product literature. The British National Formulary used to provide a table of drugs to be avoided or used with caution in pregnancy, and did so using a limited number of key phrases, but now Appendix 4 (which was the Pregnancy table) has been removed. Appendix 4 is now titled "Intravenous Additives". However, information that was previously available in the former Appendix 4 (pregnancy) and Appendix 5 (breast feeding) is now available in the individual drug monographs.
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