Breastfeeding

Lore & Background

Breast development starts in puberty with the growth of ducts, fat cells, and connective tissue. The ultimate size of the breasts is determined by the number of fat cells, but breast size is not related to a mother's breastfeeding capability or milk volume. The process of milk production, termed lactogenesis, occurs in three stages. The first stage takes place during pregnancy, allowing for the development of the breast and production of colostrum, the thick, early form of milk that is low in volume but rich in nutrition. The birth of the baby and the placenta trigger the second stage, causing milk to come in over the next several days. The third stage occurs gradually over several weeks and is characterized by a full milk supply regulated locally by the infant's demand for food. Changes in pregnancy, starting around 16 weeks gestational age, prepare the breast for lactation. These changes, collectively known as Lactogenesis I, are directed by hormones produced by the placenta and the brain, including estrogen, progesterone, and prolactin. While prolactin is the predominant hormone in milk production, progesterone blocks prolactin receptors in the breast during pregnancy, inhibiting milk from coming in until after delivery. The delivery of the placenta causes an abrupt drop in progesterone, allowing prolactin to work effectively and initiating Lactogenesis II. Oxytocin contracts the smooth muscle around milk ducts and alveoli to eject milk, a process known as the milk ejection reflex or let-down. Once milk supply is well established, the volume and content of milk produced are controlled locally. The only way to maintain milk supply is to drain the breasts frequently. Infrequent or incomplete drainage decreases blood flow to the alveoli and signals milk-producing cells to produce less milk. A condition called mastitis sometimes occurs from incomplete milk drainage. The Academy of Breastfeeding Medicine recommends against trying to empty the breasts to prevent causing milk oversupply.

Reader's Guide

Breastfeeding has a number of benefits to both the mother and the infant that infant formula lacks. Breastfeeding decreases the risk of respiratory tract infections, ear infections, sudden infant death syndrome (SIDS), and diarrhea for the baby, both in developing and developed countries. Other benefits have been proposed to include lower risks of asthma, food allergies, and diabetes. Breastfeeding may also improve cognitive development and decrease the risk of obesity in adulthood. Benefits for the mother include less blood loss following delivery, better contraction of the uterus, and a decreased risk of postpartum depression. Breastfeeding delays the return of menstruation and, in very specific circumstances, fertility, a phenomenon known as lactational amenorrhea. Long-term benefits for the mother include decreased risk of breast cancer, cardiovascular disease, diabetes, metabolic syndrome, and rheumatoid arthritis. Breastfeeding is less expensive than infant formula, but its impact on mothers' ability to earn an income is not usually factored into calculations comparing the two feeding methods. It is also common for women to experience symptoms such as vaginal dryness, De Quervain syndrome, cramping, mastitis, moderate to severe nipple pain, and a general lack of bodily autonomy. These symptoms generally peak at the start of breastfeeding but disappear or become considerably more manageable after the first few weeks. Medical conditions that do not allow breastfeeding are rare. Mothers who take certain recreational drugs should not breastfeed, however, most medications are compatible with breastfeeding. Available evidence indicates that it is unlikely that COVID-19 can be transmitted through breast milk. Smoking tobacco and consuming limited amounts of alcohol or coffee are not reasons to avoid breastfeeding.

Did You Know?

• Breastfeeding decreases the risk of respiratory tract infections, ear infections, sudden infant death syndrome (SIDS), and diarrhea for the baby.
• The size of the breast is not related to a mother's breastfeeding capability or the volume of milk she can produce.