Breastfeeding and Lactation
Lactation, the normal physiologic response of all women following childbirth, causes the mammary glands (breasts) to secrete milk. Lactation involves both milk production and milk "let-down." During pregnancy, the placenta secretes high levels of estrogen and progesterone to prepare the breasts for lactation. Following the delivery of the placenta, the sudden drop in estrogen and progesterone triggers the pituitary gland to produce the hormone prolactin that stimulates the production of milk. Infant suckling stimulates the posterior pituitary gland to produce the hormone oxytocin which allows milk to "let down" (a reflex resulting in the release of milk from the alveoli to the milk ducts of the breasts). Without continued infant suckling, milk production and let down will cease within one-2 weeks.
Mechanical methods (manual or electric pumping devices, and/or hand expression of milk) can also stimulate milk production in situations where breast feeding at birth is not possible due to maternal/newborn illness or separation. Breast pumping also enables women to breast feed infants after returning to work because women maintain an adequate milk supply and provide babies with "pumped" breast milk, if proper storage and handling of breast milk is feasible.
Benefits of Breast-feeding
Breast milk is an ideal source of nutrition for infants because it provides the baby with essential nutrients, increases immunity, may prevent the development of allergies, and helps to foster an emotional bond between the mother and newborn. Breast milk is readily available, inexpensive, and safe in most situations.
HIV infection can be transmitted from an HIV-positive woman to her baby through breast-feeding. Wherever possible, women are advised to learn their HIV status during pregnancy, so that they can make informed decisions about their pregnancy, their own health, and choices for infant feeding.
Women who are HIV-positive are advised not to breastfeed. However, in locations where the availability of clean water is limited, and/or the cost of infant formula is beyond the means of the family, HIV-positive new mothers face a difficult choice.
Unlike the United States, breast-feeding for prolonged periods is the norm in many parts of the developing world. Frequent and continuous breast-feeding without supplementation with formula or food can inhibit ovulation, which has a contraceptive effect. For women who exclusively breastfeed (breastfeed on demand), and have not yet menstruated, breast-feeding is about 98% effective in preventing pregnancy for six months post-partum. The longer a woman breastfeeds, the more likely the contraceptive benefits will wear off. In developing countries, breast-feeding plays a major role in prolonging birth intervals and reducing fertility.
In the United States and other developed countries, breast-feeding plays a smaller role in contraception because fewer women breastfeed, and/or breastfeed continuously without supplementation using infant formula.