Difference between revisions of "Lactation"

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Lactation is physiologically appropriate following childbirth.
 
Lactation is physiologically appropriate following childbirth.
 
If is occurs in other settings, it is pathophysiologic and is referred to as [[galactorrhea]]
 
If is occurs in other settings, it is pathophysiologic and is referred to as [[galactorrhea]]
Related Key Words and Synonyms:
 
  
===== References =====
+
'''Lactation''' describes the secretion of [[milk]] from the [[mammary gland]]s, the process of providing that milk to the young, and the period of time that a [[mother]] lactates to feed her young. The process occurs in all [[female]] [[mammal]]s, and in humans it is commonly referred to as [[breastfeeding]] or nursing. In most species milk comes out of the mother's [[nipples]]; however, the [[platypus]] (a non-placental mammal) releases milk through ducts in its abdomen. In only one [[species]] of mammal, the [[Dayak fruit bat]], is milk production a normal male function. In some other mammals, the male may produce milk as the result of a [[hormone]] imbalance, (for instance [[witch's milk]]).  This phenomenon may also be observed in newborn infants as well.
 +
 
 +
==Purpose==
 +
 
 +
The chief function of lactation is to provide [[nutrition]] to the young after birth. In almost all mammals lactation, or more correctly the suckling stimulus, induces a period of [[infertility]], usually by the suppression of [[ovulation]], which serves to provide the optimal birth spacing for survival of the offspring.<ref>McNeilly, A. S. 1997. Lactation and fertility. ''Journal of Mammary Gland Biology and Neoplasia'' 2:291-298 PMID 10882312</ref>
 +
 
 +
==Human lactation==
 +
 
 +
[[Image:Breastfeeding(milkfinal).png|frame|right|When the baby sucks its mother's breast, a hormone called oxytocin compels the milk to flow from the alveoli, through the ducts (milk canals) into the sacs (milk pools) behind the areola and then into the baby's mouth]]
 +
 
 +
===Hormonal influences===
 +
 
 +
From the third month of [[pregnancy]] (the second and third [[trimesters]]), a woman's body produces [[hormone]]s that stimulate the growth of the [[milk duct]] system in the [[breast]]s:
 +
*[[Progesterone]] &mdash; influences the growth in size of [[Alveolar gland|alveoli]] and lobes. Progesterone levels drop after birth. This triggers the onset of copious milk production.<ref name=Mohrbacher_2003>{{cite book | last= Mohrbacher | first= Nancy |coauthor=Stock, Julie  | title = The Breastfeeding Answer Book | edition = 3rd ed. (revised)  | publisher = La Leche League International | year =  2003 | id = ISBN 0-912500-92-1 }}</ref>
 +
*[[Estrogen]] &mdash; stimulates the milk duct system to grow and become specific. Estrogen levels also drop at delivery and remain low for the first several months of breastfeeding.<ref name=Mohrbacher_2003 /> It is recommended that breastfeeding mothers avoid estrogen-based birth control methods, as a spike in estrogen levels may reduce a mother's milk supply.
 +
*[[Follicle stimulating hormone]] (FSH)
 +
*[[Luteinizing hormone]] (LH)
 +
*[[Prolactin]] &mdash; contributes to the increased growth of the alveoli during pregnancy.
 +
*[[Oxytocin]] &mdash; contracts the [[smooth muscle]] of the [[uterus]] during and after birth, and during orgasm. After birth, oxytocin contracts the smooth muscle layer of band-like cells surrounding the alveoli to squeeze the newly-produced milk into the duct system. Oxytocin is necessary for the ''milk ejection reflex'', or ''let-down'' to occur.
 +
*[[Human placental lactogen]] (HPL) &mdash; From the second month of pregnancy, the [[placenta]] releases large amounts of HPL. This hormone appears to be instrumental in breast, nipple, and areola growth before birth.
 +
 
 +
By the fifth or sixth month of pregnancy, the breasts are ready to produce milk. It is also possible to [[#Lactation without pregnancy|induce lactation]] without pregnancy.
 +
 
 +
====Lactogenesis I====
 +
 
 +
During the latter part of pregnancy, the woman's breasts enter into the ''Lactogenesis I'' 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. 
 +
 
 +
====Lactogenesis II====
 +
 
 +
At [[Childbirth|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 ''Lactogenesis II''.
 +
 
 +
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 higher 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.<ref name="Cregan_2002">{{cite journal |author=Cregan M, Mitoulas L, Hartmann P |title=Milk prolactin, feed volume and duration between feeds in women breastfeeding their full-term infants over a 24 h period |journal=Exp Physiol |volume=87 |issue=2 |pages=207-14 |year=2002 |id=PMID 11856965}}</ref>
 +
 
 +
Other hormones&mdash;notably insulin, thyroxine, and cortisol&mdash;are also involved, but their roles are not yet well understood. Although biochemical markers indicate that Lactogenesis II begins about 30–40 hours after birth, mothers do not typically begin feeling increased breast fullness (the sensation of milk "coming in") 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 [[antibody|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 germs from invading the baby's system. Secretory IgA also helps prevent food allergies.<ref name="Sears_2002">{{cite book | last = Sears | first = Martha | coauthors = [[William Sears (physician)|Sears, William]] | title = The Breastfeeding Book | publisher = Little, Brown | year = 2000  | id = ISBN 978-0-316-77924-5 }}</ref> Over the first two weeks after the birth, colostrum production slowly gives way to mature breast milk.<ref name="Mohrbacher_2003" />
 +
 
 +
====Lactogenesis III====
 +
 
 +
The hormonal [[endocrine]] control system drives milk production during pregnancy and the first few days [[postpartum|after the birth]]. When the milk supply is more firmly established, [[autocrine]] (or local) control system begins. This stage is called ''Lactogenesis III''
 +
 
 +
During this stage, the more that milk is removed from the breasts, the more the breast will produce milk.<ref name=deCarvalho_1985>{{cite journal |author=deCarvalho M, Anderson D, Giangreco A, Pittard W |title=Frequency of milk expression and milk production by mothers of non-nursing premature neonates |journal=Am J Dis Child |volume=139 |issue=5 |pages=483-5 |year=1985 |id=PMID 3984973}}</ref><ref name=Hopkinson_1988>{{cite journal |author=Hopkinson J, Schanler R, Garza C |title=Milk production by mothers of premature infants |journal=Pediatrics |volume=81 |issue=6 |pages=815-20 |year=1988 |id=PMID 3368280}}</ref> Research also suggests that draining the breasts more fully also increases the rate of milk production.<ref name=Daly_1993>{{cite journal |author=Daly S, Owens R, Hartmann P |title=The short-term synthesis and infant-regulated removal of milk in lactating women |journal=Exp Physiol |volume=78 |issue=2 |pages=209-20 |year=1993 |id=PMID 8471241}}</ref> 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:
 +
* not feeding or [[breast pump|pumping]] often enough
 +
* inability of the infant to transfer milk effectively caused by, among other things:
 +
** jaw or mouth structure deficits
 +
** poor latching technique
 +
* rare maternal endocrine disorders
 +
* hypoplastic breast tissue
 +
* a metabolic or digestive inability in the infant, making it unable to digest the milk it receives
 +
* inadequate calorie intake or malnutrition of the mother
 +
 
 +
===Milk ejection reflex===
 +
 
 +
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.
 +
 
 +
The let-down reflex is not always consistent, especially at first. The thought of breastfeeding or the sound of any baby 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 (medicine)|Stress]] or anxiety can cause difficulties with breastfeeding.
 +
 
 +
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.
 +
 
 +
===Afterpains===
 +
 
 +
The surge of oxytocin that triggers the milk ejection reflex 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.<ref name="Kathy Fray">{{cite book | last = Fray | first = Kathy | title = Oh Baby...Birth, Babies & Motherhood Uncensored |  publisher = Random House NZ | year = 2005 | id = ISBN 1-86941-713-5 }}</ref>
 +
 
 +
===Lactation without pregnancy===
 +
 
 +
Women who have never been [[pregnant]] are sometimes able to induce enough lactation to breastfeed. This is called "induced lactation". A woman who has breastfed before and re-starts is said to "relactate". If the nipples are consistently stimulated by a breast pump or actual suckling, the breasts will eventually begin to produce enough milk to begin feeding a baby. Once established, lactation adjusts to demand. This is how some [[adoption|adoptive mothers]], usually beginning with a supplemental nursing system or some other form of supplementation, can breastfeed.<ref>[http://www.fourfriends.com/abrw/ http://www.fourfriends.com/abrw/] ''Fourfriends.com'' </ref> There is thought to be little or no difference in milk composition whether lactation is induced or a result of pregnancy. Rare accounts of [[male lactation]] (as distinct from [[galactorrhea]]) exist in the medical literature.
 +
 
 +
Some drugs, primarily [[atypical antipsychotics]] such as [[Risperdal]], may cause lactation in both women and men. Also, some couples may use lactation for [[Erotic lactation|sexual purposes]].
 +
 
 +
== References ==
 +
 
 +
<references />
 +
 
 +
[[bs:Dojenje]]
 +
[[da:Amning]]
 +
[[de:Laktation]]
 +
[[es:Lactancia materna]]
 +
[[fr:Lactation]]
 +
[[it:Allattamento materno]]
 +
[[he:הנקה]]
 +
[[lt:Žindymas]]
 +
[[nl:Borstvoeding]]
 +
[[ja:授乳]]
 +
[[no:Amming]]
 +
[[pl:Laktacja]]
 +
[[pt:Aleitamento]]
 +
[[ru:Грудное вскармливание]]
 +
[[fi:Imetys]]
 +
[[sv:Amning]]
 +
[[uk:Лактація]]
 +
[[zh:母乳喂养]]
  
 
== Epidemiology and Demographics ==
 
== Epidemiology and Demographics ==

Revision as of 13:11, 9 September 2007

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Contents

Overview

Lactation is physiologically appropriate following childbirth. If is occurs in other settings, it is pathophysiologic and is referred to as galactorrhea

Lactation describes the secretion of milk from the mammary glands, the process of providing that milk to the young, and the period of time that a mother lactates to feed her young. The process occurs in all female mammals, and in humans it is commonly referred to as breastfeeding or nursing. In most species milk comes out of the mother's nipples; however, the platypus (a non-placental mammal) releases milk through ducts in its abdomen. In only one species of mammal, the Dayak fruit bat, is milk production a normal male function. In some other mammals, the male may produce milk as the result of a hormone imbalance, (for instance witch's milk). This phenomenon may also be observed in newborn infants as well.

Purpose

The chief function of lactation is to provide nutrition to the young after birth. In almost all mammals lactation, or more correctly the suckling stimulus, induces a period of infertility, usually by the suppression of ovulation, which serves to provide the optimal birth spacing for survival of the offspring.[1]

Human lactation

When the baby sucks its mother's breast, a hormone called oxytocin compels the milk to flow from the alveoli, through the ducts (milk canals) into the sacs (milk pools) behind the areola and then into the baby's mouth

Hormonal influences

From the third month of pregnancy (the second and third trimesters), a woman's body produces hormones that stimulate the growth of the milk duct system in the breasts:

  • Progesterone — influences the growth in size of alveoli and lobes. Progesterone levels drop after birth. This triggers the onset of copious milk production.[2]
  • Estrogen — stimulates the milk duct system to grow and become specific. Estrogen levels also drop at delivery and remain low for the first several months of breastfeeding.[2] It is recommended that breastfeeding mothers avoid estrogen-based birth control methods, as a spike in estrogen levels may reduce a mother's milk supply.
  • Follicle stimulating hormone (FSH)
  • Luteinizing hormone (LH)
  • Prolactin — contributes to the increased growth of the alveoli during pregnancy.
  • Oxytocin — contracts the smooth muscle of the uterus during and after birth, and during orgasm. After birth, oxytocin contracts the smooth muscle layer of band-like cells surrounding the alveoli to squeeze the newly-produced milk into the duct system. Oxytocin is necessary for the milk ejection reflex, or let-down to occur.
  • Human placental lactogen (HPL) — From the second month of pregnancy, the placenta releases large amounts of HPL. This hormone appears to be instrumental in breast, nipple, and areola growth before birth.

By the fifth or sixth month of pregnancy, the breasts are ready to produce milk. It is also possible to induce lactation without pregnancy.

Lactogenesis I

During the latter part of pregnancy, the woman's breasts enter into the Lactogenesis I 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.

Lactogenesis II

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 Lactogenesis II.

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 higher 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.[3]

Other hormones—notably insulin, thyroxine, and cortisol—are also involved, but their roles are not yet well understood. Although biochemical markers indicate that Lactogenesis II begins about 30–40 hours after birth, mothers do not typically begin feeling increased breast fullness (the sensation of milk "coming in") 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 germs from invading the baby's system. Secretory IgA also helps prevent food allergies.[4] Over the first two weeks after the birth, colostrum production slowly gives way to mature breast milk.[2]

Lactogenesis III

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. This stage is called Lactogenesis III

During this stage, the more that milk is removed from the breasts, the more the breast will produce milk.[5][6] Research also suggests that draining the breasts more fully also increases the rate of milk production.[7] 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:

  • not feeding or pumping often enough
  • inability of the infant to transfer milk effectively caused by, among other things:
    • jaw or mouth structure deficits
    • poor latching technique
  • rare maternal endocrine disorders
  • hypoplastic breast tissue
  • a metabolic or digestive inability in the infant, making it unable to digest the milk it receives
  • inadequate calorie intake or malnutrition of the mother

Milk ejection reflex

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.

The let-down reflex is not always consistent, especially at first. The thought of breastfeeding or the sound of any baby 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.

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.

Afterpains

The surge of oxytocin that triggers the milk ejection reflex 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.[8]

Lactation without pregnancy

Women who have never been pregnant are sometimes able to induce enough lactation to breastfeed. This is called "induced lactation". A woman who has breastfed before and re-starts is said to "relactate". If the nipples are consistently stimulated by a breast pump or actual suckling, the breasts will eventually begin to produce enough milk to begin feeding a baby. Once established, lactation adjusts to demand. This is how some adoptive mothers, usually beginning with a supplemental nursing system or some other form of supplementation, can breastfeed.[9] There is thought to be little or no difference in milk composition whether lactation is induced or a result of pregnancy. Rare accounts of male lactation (as distinct from galactorrhea) exist in the medical literature.

Some drugs, primarily atypical antipsychotics such as Risperdal, may cause lactation in both women and men. Also, some couples may use lactation for sexual purposes.

References

  1. McNeilly, A. S. 1997. Lactation and fertility. Journal of Mammary Gland Biology and Neoplasia 2:291-298 PMID 10882312
  2. 2.0 2.1 2.2 Mohrbacher, Nancy (2003). The Breastfeeding Answer Book (3rd ed. (revised) ed.). La Leche League International. ISBN 0-912500-92-1. Unknown parameter |coauthor= ignored (help)
  3. Cregan M, Mitoulas L, Hartmann P (2002). "Milk prolactin, feed volume and duration between feeds in women breastfeeding their full-term infants over a 24 h period". Exp Physiol. 87 (2): 207–14. PMID 11856965.
  4. Sears, Martha (2000). The Breastfeeding Book. Little, Brown. ISBN 978-0-316-77924-5. Unknown parameter |coauthors= ignored (help)
  5. deCarvalho M, Anderson D, Giangreco A, Pittard W (1985). "Frequency of milk expression and milk production by mothers of non-nursing premature neonates". Am J Dis Child. 139 (5): 483–5. PMID 3984973.
  6. Hopkinson J, Schanler R, Garza C (1988). "Milk production by mothers of premature infants". Pediatrics. 81 (6): 815–20. PMID 3368280.
  7. Daly S, Owens R, Hartmann P (1993). "The short-term synthesis and infant-regulated removal of milk in lactating women". Exp Physiol. 78 (2): 209–20. PMID 8471241.
  8. Fray, Kathy (2005). Oh Baby...Birth, Babies & Motherhood Uncensored. Random House NZ. ISBN 1-86941-713-5.
  9. http://www.fourfriends.com/abrw/ Fourfriends.com

bs:Dojenje da:Amning de:Laktation it:Allattamento materno he:הנקה lt:Žindymas nl:Borstvoeding no:Amming fi:Imetys sv:Amning uk:Лактація

Epidemiology and Demographics

References

Risk Factors

References

Screening

References

Pathophysiology & Etiology

References

Molecular Biology

References

Genetics

References

Natural History

References

Diagnosis

Differential Diagnosis

References

History and Symptoms

References

Physical Examination

Appearance of the Patient

Vital Signs

Skin

Eyes

Ear Nose and Throat

Heart

Lungs

Abdomen

Extremities

Neurologic

Other

References

Laboratory Findings

Electrolyte and Biomarker Studies

References

Electrocardiogram

References

Chest X Ray

References

MRI and CT

References

Echocardiography or Ultrasound

References

Other Imaging Findings

References

Other Diagnostic Studies

References

Risk Stratification and Prognosis

References

Treatment

Pharmacotherapy

Acute Pharmacotherapies

References

Chronic Pharmacotherapies

References

Surgery and Device Based Therapy

Indications for Surgery

References

Pre-Operative Assessment

References

Post-Operative Management

References

Transplantation

References

Primary Prevention

References

Secondary Prevention

References

Cost-Effectiveness of Therapy

References

Future or Investigational Therapies

References

"The Way I Like To Do It ..." Tips and Tricks From Clinicians Around The World

Suggested Revisions to the Current Guidelines

References

<biblio>

</biblio>

Acknowledgements

The content on this page was first contributed by: C. Michael Gibson, M.S., M.D.

List of contributors:

Suggested Reading and Key General References

Suggested Links and Web Resources

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