Lactation refers to the formation of milk in the breasts during the period following childbirth . Breastfeeding is the process of the infant obtaining milk by suckling at the breast.


Although breast development begins around puberty , development of mammary function is only completed in pregnancy. During the first half of pregnancy the mammary ducts proliferate and group together to form large lobules. During the second half of pregnancy, secretory activity increases and the alveoli become distended by accumulating colostrum. After 16 weeks of pregnancy, lactation occurs even if the pregnancy does not progress.

The ability of the mammary gland to secrete milk during later pregnancy is called lactogenesis, stage 1. During this time, breast size increases and fat droplets accumulate in the secretory cells. The onset of copious milk secretions after birth is lactogenesis, stage 2, and usually occurs from day two or three to eight days postpartum. During this time, the milk goes through a maturation process to match the infant's needs. Without the hormone prolactin, lactation would not occur. During pregnancy prolactin helps to increase breast mass but does not cause lactation because it is inhibited by the hormone progesterone, which is made by the placenta. The inhibiting influence of progesterone is so strong that lactation is delayed if any of the placenta is retained after birth. Prolactin levels rise and fall in direct proportion to the frequency, intensity, and duration of nipple stimulation from the infant's suckling. During the first week after birth, prolactin levels in breastfeeding women fall about 50 percent. If a mother does not breastfeed, prolactin levels usually reach the levels of the nonpregnant state by seven days postpartum. After milk "comes in" or rapidly increases in volume, lactation is no longer driven by the hormone prolactin. It shifts control to a milk removal driven process, i.e., sucking stimulus. Thus, the initiation of lactation is not driven by breastfeeding, but breastfeeding is necessary for the continuation of lactation.

The breast is not a passive container of milk. It is an organ that actively produces milk due to the stimulus of the infant's sucking; the removal of milk from the breasts causes continued milk production. It is a supply and demand response that regulates the production of milk to match the intake of the infant. The composition of breast milk changes to meet the specific needs of the growing infant. In response to suckling, the hormone oxytocin causes the milk ejection reflex or "let-down" reflex to occur. Milk ejection is the forceful expulsion of milk from the alveoli openings. Oxytocin secretion is also nature's way of causing a woman's uterus to contract after birth to control postpartum bleeding and assist in uterine involution. These contractions can continue for up to 20 minutes after feeding and may be painful during the first few days. The benefit of this, however, is that uterine discharge diminishes faster and the uterine involution occurs more quickly.

Colostrum is thick and creamy yellow as compared with mature milk, which is thin and bluish-white. Compared with mature milk, colostrum is richer in protein and minerals and lower in carbohydrates, fat, and some vitamins . The high concentration of total protein and minerals in colostrum gradually changes to meet the infant's needs over the first two to three weeks until lactation is established. The key component in colostrum and breast milk is immunoglobulins or antibodies that serve to protect the infant against infections or viruses. Breast milk also facilitates the development of the infant's own immune system to mature faster. As a result, breast-fed babies have fewer ear infections, diarrhea , rashes , allergies , and other medical problems than bottle-fed babies. Human milk is rich in proteins, lipids, carbohydrates, vitamins, minerals, hormones, enzymes, growth factors, and many types of protective agents. It contains about 10 percent solids for energy and growth and the rest is water, which is essential to maintain hydration. This is also why a breastfed baby does not need additional water. Infants can digest breast milk much more rapidly than formula and, therefore, do not get constipated. On average, it takes about 30 minutes longer to digest formula as opposed to breast milk. Breastfed babies have better cheekbone development and better jaw alignment.

Besides the benefits of the contracting uterus, the process of producing milk burns calories, which helps the mother to lose excess weight gained during pregnancy. After all, that is why pregnant women put on extra fat during pregnancy—energy storage for milk production. Breastfeeding is also related to a lower risk of breast cancer and ovarian cancer. For every year of life spent breastfeeding, a woman's risk of developing breast cancer drops by 4.3 percent and this is on top of the 7 percent reduction she enjoys for every baby to whom she gives birth.

Additionally, there is the convenience. Breast milk is always with the mother. Mothers do not have to store it. It is always at the right temperature. It is free. It does not require sterilization. In fact, it prevents diseases and has protective factors resulting in healthier babies and decreased healthcare costs. It saves money as there is no need to buy formula, bottles, and nipples.


It is best to begin breastfeeding immediately after birth as it is an infant's natural instinct to nurse then. Regardless of the baby's initial suckling behavior, this interaction stimulates uterine contractions, promotes colonization of harmless bacteria on the nipple, and helps to protect the infant from pathogenic bacteria. It is an important time to nuzzle. Women breastfeed for a longer duration if feedings are started early. The first several feedings have an imprinting effect. It is recommended to continue feeding about every two to three hours. It is important to remember that all babies are different; some need to nurse almost constantly at first, while others can go much longer between feedings. There are babies and mothers who have no trouble breastfeeding, while others may need some assistance. Once the baby begins to suck, the mother makes sure that the entire dark area around the nipple (areola) is in the baby's mouth. This helps stimulate milk flow and allows the baby to get enough milk. Nipple soreness can be a result of the infant not getting a good grasp of the entire areola. A newborn needs to be fed at least eight to 12 times in 24 hours. Since breast milk is so easily digested, a baby may be hungry again as soon as one and one-half hours after the last feeding.

Mothers need to be comfortable when nursing; therefore, loose, front-opening clothes and a good nursing bra are essential. They need to explore different positions for breastfeeding to determine what is best for them. The cradle hold works well in bed or sitting in a comfortable chair. The football hold is excellent if the woman had a cesarean section . The mother can use pillows to support the baby and a footstool to flatten her

(Table by GGS Information Services.)
(Table by GGS Information Services.)

Signs of good breastfeeding  
progress Warning signs  
Eight to 12 feeding per 24 Fewer than eight feedings in 24 hours;
hours baby sleeps four to six hours at time
Baby nurses every 1.5 to Baby nurses every hour or more, but
three hours never seems satisfied
Six to eight wet diapers every Fewer than six wet diapers after the
24 hours after the third day third day
Soft yellow stools, about 1 Dark black, green, or brown stools
tablespoon or larger after the third day
After the third day, four to 10 Fewer than three or four stools per
stools per day day after the third day
Average daily weight gain of Baby does not regain birth weight by
15 to 30 g once milk comes in 10 days of age
Milk comes in; breasts are full Milk does not seem to come in by the
and warm and may leak milk fifth day
Intermittent periods of rhythmic Milk comes in, but sucking or
sucking and audible swallows swallowing is not audible
Breasts are tender and may be Sore and painful nipples throughout
slightly painful or sore most feedings; scabbed or cracked
Breasts soften after a feed Severe engorgement; breast remain
  very hard after a feed

lap. The mother can position the baby's head by snuggling it in one arm and supporting her breast with the other hand by keeping her thumb well above the areola and the rest of the fingers below and under the breast (sometimes called the C-hold). In this position, the mother can lift her breast and guide her nipple in any direction as she helps the baby to take in more of the areola.

For early feedings, the infant should be offered both breasts at each feeding as this stimulates the need-supply response. The length of the feeding is up to the mother. The general rule is to watch the baby, not the clock. If, however, it is a first time mother, 20 to 30 minutes on the first side can be suggested. If the baby falls asleep at the breast, the next feeding should begin with the breast that was not nursed. Mothers can tell if the baby is getting enough milk by checking diapers; a baby who is wetting between four to six disposable diapers (six to eight cloth) and who has three or four bowel movements in 24 hours is getting enough milk.

Common problems

New mothers may experience nursing problems, including the following:

When an infant is properly latched onto the breast, the babys nose touches (or nearly touches) the breast. He or she takes the entire areola into the mouth, facilitating the intake of milk far back into the throat. (Illustration by GGS Informat
When an infant is properly latched onto the breast, the baby's nose touches (or nearly touches) the breast. He or she takes the entire areola into the mouth, facilitating the intake of milk far back into the throat.
(Illustration by GGS Information Services.)

  • Engorgement: Breasts that are too full can prevent the baby from suckling because they cannot be grasped. Expressing milk manually or with a breast pump can alleviate this problem.
  • Sore nipples: Transient soreness can occur during the first week postpartum and is usually temporary. Air drying the nipples and rubbing colostrum or breast milk into them provides relief. Prolonged, abnormal soreness lasts longer than a week postpartum. Discontinuing use of soap on breasts while bathing and applying purified lanolin to nipples and air drying them helps.
  • Infection: Soreness and inflammation on the breast surface or a fever in the mother may be an indication of breast infection (mastitis). If it is just starting, the mother should drink lots of water and nurse frequently on the affected breast. Antibiotics may be necessary if the infection persists.

Lactation consultants work at almost every hospital where babies are delivered. First-time mothers can request the lactation consultant to visit her. The mother should make a note of the lactation consultant's phone number should problems be encountered after mother and infant go home.

There are no rules about when to stop breastfeeding. A baby needs breast milk for at least the first year of life and it is preferred that no solid food be given for at least the first six months to prevent allergies. As long as a baby eats age-appropriate solid food, the mother may nurse for several years.

Parental concerns

The majority of illnesses are not transmitted via breast milk; in fact, breast milk prevents many illnesses. However, some viruses, including HIV (the virus that causes AIDS can be passed in breast milk; for this reason, women who are HIV-positive should not breastfeed unless they are living in a country that does not have clean water to make formula. A lack of clean water to make formula could result in an infant dying from diarrhea.

Many medications have not been tested in nursing women, so it is not certain what drugs can affect a breastfed child. A nursing woman should always check with her doctor or lactation consultant before taking any medications, including over-the-counter drugs. The mother can usually take antibiotics without discontinuing breastfeeding.

The following drugs are not safe for a mother to take while she is nursing:

  • radioactive drugs for some diagnostic tests
  • chemotherapy drugs for cancer
  • bromocriptine
  • ergotamine
  • lithium
  • methotrexate
  • street drugs (including marijuana, heroin, amphetamines)
  • tobacco


Alveoli —The tiny air sacs clustered at the ends of the bronchioles in the lungs in which oxygen-carbon dioxide exchange takes place.

Bromocriptine —Also known as Parlodel, it is a dopamine receptor agonist used to treat galactorrhea by reducing levels of the hormone prolactin and is also used to treat Parkinson's disease.

Colostrum —Milk secreted for a few days after birth and characterized by high protein and antibody content.

Ergotamine —A drug used to prevent or treat migraine headaches. It can cause vomiting, diarrhea, and convulsions in infants and should not be taken by women who are nursing.

Involution —The return of a large organ to normal size.

Lactogenesis —The initiation of milk secretion.

Lithium —A medication prescribed to treat the manic (excited) phases of bipolar disorder.

Mammary —Relating to the breast.

Methotrexate —A drug that interferes with cell growth and is used to treat rheumatoid arthritis as well as various types of cancer. Side-effects may include mouth sores, digestive upsets, skin rashes, and hair loss. Since this drug can supress an infant's immune system, it should not be taken by nursing mothers.

Placenta —The organ that provides oxygen and nutrition from the mother to the unborn baby during pregnancy. The placenta is attached to the wall of the uterus and leads to the unborn baby via the umbilical cord.

Postpartum —After childbirth.

Progesterone —The hormone produced by the ovary after ovulation that prepares the uterine lining for a fertilized egg.

Prolactin —A hormone that helps the breast prepare for milk production during pregnancy.



Behrmann, Barbara L. The Breastfeeding Café: Mothers Share the Joys, Challenges, and Secrets of Nursing. Ann Arbor, MI: University of Michigan Press, 2005.

Hanson, Lars A. Immunobiology of Human Milk: How Breastfeeding Protects Babies. Armillo, TX: Pharmasoft Publishing, 2004.

La Leche League International Staff. The Womanly Art of Breastfeeding. East Rutherford, NJ: Penguin Group, 2004.

Lim, Robin. Eating for Two: Recipes for Pregnant and Breastfeeding Women. Berkeley, CA: Celestial Arts Publishing, 2004.

Olds, Sally, et al. Maternal-Newborn Nursing & Women's Health Care , 7th ed. Saddle River, NJ: Prentice Hall, 2004.

Riordan, Jan. Breastfeeding and Human Lactation , 3rd ed. Boston, MA: Jones and Bartlett Publishers, 2004.


International Lactation Consultants Association. 1500 Sunday Drive, Suite 102; Raleigh, NC 27607. Web site:

La Leche League International. 1400 North Meacham Rd., Schaumburg, IL 60173. Web site:

National Alliance for Breastfeeding Advocacy. 9684 Oak Hill Drive; Ellicott City, MD 21042. Web site:

Linda K. Bennington

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Also read article about Lactation from Wikipedia

User Contributions:

Report this comment as inappropriate
Aug 6, 2009 @ 8:08 am
I nursed my children, however my sister just had a child at the age of 37 and her labor was induced. Does that prohibit her milk from coming in, because she is struggling with that?


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