The phrase uttered most frequently by occasional visitors to the home of an infant is "My, hasn't he grown!" A perceptive individual who has not seen a particular infant for more than two to three weeks is often astounded by the growth during such a brief period. Infancy is a time of extraordinary growth in height and weight and dramatic changes in body proportion.


The average newborn weighs 7 1/2 pounds and measures about 20 inches from head to toe. In the next two years, the infant will grow faster than at any later period, including adolescence. Birth-weight typically doubles by five months (to 15 pounds) and triples by the first birthday (to 22 pounds). The baby gains only 5 to 6 pounds in the second year, and 4 to 5 pounds in the third year. Height increases by about half in the wpe11.jpg (5084 bytes)first year (to 30 inches) and by an additional 5-6 inches in the second year. Despite the overall rapid growth during the first two years, the rate of growth



tapers off from the first to the second year. It has been shown that a babies tend to grow in spurts, rather than in an even progression (Lampl et al., 1992). For example, a baby might not grow at all for several days or weeks, followed by sudden growth of up to an inch in 24 hours!

This rapid growth is a challenge to the physical strength of caregivers, particularly parents. The five-month-old weighs about as much as an average bag of groceries. That may not seem like much of a challenge - until one considers what it would be like to add about 4 to five ounces to that bag each week, especially if you must carry the bag with you wherever you go. Parents must gain in muscle strength with the increasing weight of the baby, and some suffer from the physical strain. A small industry has emerged in recent years for the manufacture of devices such as slings, backpacks, and infant seats to assist parents in transporting their increasingly heavy babies.


The body proportions of the newborn and infant are dramatically different from the proportions of an adult. Figure 6.1 provides an artist's representation of the changes in body proportions from the infant period to adulthood. These changes progress according to the two fundamental principles of physical growth:. First, by the cephalocaudal (Latin for head-to-tail) principle, growth of the head and upper body precede growth in the lower body. Eight weeks after conception, the head is half of the fetus' length; at birth it is only 25% of the body length but still roughly the length of its legs. By adulthood, the head accounts for only 12% of body length, whereas and the legs account for for about 50%.

Second, by the proximodistal (near-to-far) principle, the body grows from the center outward. Prenatally as well as during early childhood, the torso develops prior to the arms and legs, and the arms and legs develop prior to the hands and fingers. This principle reverses just before puberty when the hands and feet grow rapidly to mature size before other parts of the body (Tanner, 1978).


As your baby grows and begins to crawl, creep, walk, and run around your house, she will be become increasingly susceptible to accidents and injury. To ensure her safety, you must take a collective set of precautions known as "childproofing." Light sockets must be covered by protective caps, stairs and dropoffs blocked by secure gates, and dangerous objects (e.g., knives and tools) and substances (e.g., wpe11.jpg (5084 bytes)bleach and insecticides) securely stored. Childproofing requires progressive adjustment and elaboration synchronized to the rapidly increasing ability of the infant and toddler to defeat the protective hardware typically employed by parents and caregivers in day care facilities.



Is breast milk better for the baby than formula? Although the breast milk of a healthy, well-nourished mother contains all of the required nutrients in perfect proportion to the infant's needs during the first 3-4 months of life, formulas made of modified cow's milk are nutritionally acceptable for babies of mothers who cannot or choose not to breast-feed. The infant's needs for fats, protein,carbohydrates, minerals, and vitamins are adequately met by both human milk and formula. However, extensive research has shown that breast milk offers several important health advantages over formula:

There is increasing evidence that breast-feeding promotes the early development of the infant's brain and on has positive effects on long-term cognitive-intellectual development. One recent study showed that 2-month-old babies who were exclusively breast fed showed more optimal brain development than babies who were bottle fed (formula) or never breast fed (Herba and others, 2013). A similar positive effect was demonstrated in exclusively breast fed babies who were born premature (Isaacs and others, 2010). In this study, the positive effects on brain development were still wpe11.jpg (5084 bytes)present when these children were 7-8 years old.

There is also considerable evidence that breastmilk offers the baby a distinct immunological benefit that cannot be duplicated in formula. The infant's immune system does not become effective until the middle of the first year, leaving the infant vulnerable to infection. Immunological protection can be transmitted to the infant in the colostrum, a thin, yellowish fluid secreted by the breast for several days before milk is produced. Colostrum contains antibodies which cannot be duplicated in infant formula. This advantage is supported by evidence that breast-fed babies are hospitalized less than bottle-fed infants during the first 18 months of life. In one study, infants who were exclusively breast fed for the first 4 months were 72% less likely to be hospitalized for respiratory illness and 64% for gastrointestinal disorders as compared to formula fed infants (Ip and others, 2009). This study also showed a 36% reduction in the incidence of Sudden Infant Death Syndrome and a 30% decrease in the incidence of Type 1 Diabetes for babies who were exclusively breast fed for at least 3 months. Infants who are breast fed also show lower rates of obesity in childhood and adolescence. In one recent study (McCrory & Layte, 2012), infants who were breast fed more than 25 week were 50% less likely to be obese at age 9! There is also some suggestive evidence that children who are breast fed a somewhat less likely to develop Attention Deficit Hyperactivity Disorder (ADHD) at adolescence (Mimouni-Bloch and others, 2013).

The benefits of breast feeding also extend to the mothers. Mothers who breast-fed return more quickly to their pre-pregnancy weight. There is also evidence of lower rates of breast cancer (Newcomb and others, 1994) and ovarian cancer in mothers who breast-feed compared to those who do not (Reasonable & Thomas, 1993).

Based on this research and numerous other studies, the American Academy of Pediatrics recommends that mothers breast-feed their infants exclusively for the first six months of life, and to continue to breast-feed for 6 months or longer after solid foods are introduced (American Academy of Pediatrics: Policy Statement, 2012). However, despite the strong evidence in favor or breast-feeding, only about 79% of woman initiate the practice with their infants with considerable variation among racial and socioeconomics groups in the United States. By the time babies are 6 months old, less than 50% of babies continue to be breastfed (CDC, 2014.) It can be concluded, therefore, that the public health benefits of breast-feeding are still ignored by significant segments of the U.S. population.

In general, parents should not rely on their own intuition or on unreliable sources in establishing good nutrition for their infants. In particular, parents should avoid feeding their infants as they feed themselves. In one study, seven infants were identified who had been inadvertently malnourished by their overzealous, health-conscious parents. These parents placed their infants on low-fat, low-calorie diets in the mistaken belief that what is good for the parent is necessarily good for the infant (Lifshitz et al., 1987). You can avoid placing your infant's health at risk by following your pediatrician's advice on your infant's changing nutritional needs.