SUMMARY

Body Changes

1. In the first two years of life, infants grow taller, gain weight, and increase in head circumference—all indicative of development. Birthweight doubles by 4 months, triples by 1 year, and quadruples by 2 years.

2. Medical checkups in the first months of a child’s life focus especially on weight, height, and head circumference, because early detection of slow growth can halt later problems.

3. The amount of time a child sleeps gradually decreases over the first two years. Bed-sharing is the norm in many developing nations, and co-sleeping is increasingly common in developed ones.

Brain Development

4. Brain size increases dramatically, from about 25 to 75 percent of the adult brain’s weight in the first two years. Complexity increases as well, with cell growth, development of dendrites, and formation of synapses. Both growth and pruning aid cognition.

5. Experience is vital for brain development. An infant who is socially isolated, over-stressed, or deprived of stimulation may be impaired lifelong.

Perceiving and Moving

6. At birth, the senses already respond to stimuli. Prenatal experience makes hearing the most mature sense. Vision is the least mature sense at birth, but it improves quickly. Infants use all their senses to strengthen their early social interactions.

7. Infants gradually improve their motor skills as they begin to grow and brain maturation continues. Gross motor skills are soon evident, from rolling over to sitting up (at about 6 months), from standing to walking (at about 1 year), from climbing to running (before age 2).

8. Babies gradually develop the fine motor skills to grab, aim, and manipulate almost anything within reach. Experience, time, motivation, and practice allow infants to advance in all their motor skills.

Surviving in Good Health

9. About 2 billion infant deaths have been prevented in the past half-century because of improved health care. One major innovation is immunization, which has eradicated smallpox and virtually eliminated polio and measles. More medical professionals are needed to prevent, diagnose, and treat the diseases that still cause many infant deaths in poor nations.

10. Breast-feeding is best for infants, partly because breast milk helps them resist disease and promotes growth of every kind. Most babies are breast-fed at birth, but in North America only half are breast-fed at six months, and few of those are exclusively breast-fed, as doctors worldwide recommend.

11. Severe malnutrition stunts growth and can cause death, both directly through marasmus or kwashiorkor and indirectly through vulnerability if a child catches measles, an intestinal virus, or some other illness.