How much do babies grow during infancy?
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Infancy is the time period between birth and a baby’s first birthday. At no other time in life are nutritional needs higher per body weight. Infants will usually double their birth weight by the time they are halfway through their first year of life. Furthermore, they can easily triple their birth weight by their first birthday. At the same time, an infant will increase its length by roughly 50 percent by his or her first birthday. Also, the head is relatively huge at birth, maybe accounting for one-third to one-quarter of the infant’s length. Since an adult’s head is only one-eighth of his or her height it is no wonder an infant cannot support the weight of its head for a month or so after being born. |
Pediatricians and parents can check changes in weight, length, and head circumference against normal growth patterns. Generally, breast milk or formula meets an infant’s nutritional needs during the first four to six months. Thereafter, the introduction of solid foods becomes a strong nutrient contributor.
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Boys |
Girls |
What is lactation?
One of the changes that occur in a female during pregnancy is an enhancement of breast tissue and the maturing of the mammary glands. This occurs due to hormonal changes during pregnancy. Lactation is a period of time when a woman is producing breast milk in her mammary glands. Increases in the level of the hormone prolactin in a female stimulates her mammary glands to produce milk. The suckling of an infant helps signal her pituitary gland to release more prolactin into her blood and is required for continued lactation.
Breast milk is not a single substance, as it changes in composition not only with time after birth but also during a single feeding. In the first few days after birth, mothers produce a very sophisticated form of breast milk called colostrum. Over the next two weeks or so of lactation, breast milk slowly loses many of the characteristics of colostrum and gains those of mature breast milk.
What is colostrum?
Colostrum is a yellowish, viscous solution that contains more than nutrients; it also contains immune factors. These immune factors include antibodies and other factors that can help boost an infant’s developing immune capabilities. Since the infant’s digestive tract is mostly unused during pregnancy, it is relatively immature at birth and will take the first few months after birth to develop. Many of the immune factors present in colostrum pass through the infant’s immature digestive tract wall intact and enter the blood. The immune factors in colostrum are believed to contribute to the fewer lung and intestinal infections observed in breast-fed infants versus formula-fed infants. Further, factors in breast milk seem to promote the formation of a healthy colon bacteria population, since an infant’s digestive tract is also born sterile (without bacteria).
What is breast milk?
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Mature breast milk is a thinner and almost translucent solution. It is not uncommon for it to present a slightly bluish tinge. Mature breast milk contains a greater ratio of whey to casein protein versus cow’s milk. Infants digest whey protein more easily, whereas casein tends to form a curd during digestion. Mature breast milk also contains a protein called lactoferrin, which can bind iron and potentially reduce bacterial infections. This is because bacteria require iron to reproduce. In addition, the amino acid called taurine is also present in breast milk. Taurine is not used to make proteins, but it is necessary for proper bile formation and visual processes. |
The fat content of mature breast milk increases during a single feeding. This is an excellent reason to encourage an infant to feed for longer periods of time (> 10 minutes). Infants need this energy-dense liquid available later in a feeding to help meet their needs for growth and development. Further, mature human breast milk contains linoleic acid and cholesterol, both of which are necessary for the proper growth of an infant’s brain and other nervous tissue.
Lactose is the major carbohydrate in mature breast milk. You will remember that lactose is a disaccharide made up of the monosaccharides glucose and galactose. Beyond providing energy, galactose also seems to be important for the development of the insulating wrapping around nerve cells. Only small amounts of vitamin D are present in mature breast milk, so a supplement may be necessary, especially if an infant has minimal exposure to sunlight. Also, because the iron composition is also very low in breast milk, infants may benefit from a supplement by their second to third month.
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