Body Changes

In infancy, growth is so rapid and the consequences of neglect so severe that gains are closely monitored. Medical checkups, including measurement of height, weight, and head circumference, provide the first clues as to whether an infant is progressing as expected—or not.

Body Size


Video: Physical Development in Infancy and Childhood offers a quick review of the physical changes that occur in a child’s first two years.

Newborns lose several ounces in the first three days and then gain an ounce a day for months. Birthweight typically doubles by 4 months and triples by a year. On average, a 7-pound newborn will be 21 pounds at 12 months (9,525 grams, up from 3,400 grams grams at birth). Height increases, too: A typical baby grows 10 inches (24 centimeters) in a year.

Physical growth then slows, but not by much. Most 24-month-old children weigh almost 28 pounds (13 kilograms) and have added another 4 inches (10 centimeters) or so. Typically, 2-year-olds are half their adult height and about one-fifth their adult weight, four times heavier than they were at birth (see Figure 5.1).

FIGURE 5.1
Eat and Sleep The rate of increasing weight in the first weeks of life makes it obvious why new babies need to be fed day and night.

At each well-baby checkup (monthly at first), growth is compared to the baby’s previous numbers. Often, measurements are expressed as a percentile, from 0 to 100, that indicates where an individual ranks on a particular measure. Percentiles are often used for school achievement; here they are used to indicate how an infant’s growth compares to other babies of the same age.

Thus, a 3-month-old’s weight at the 30th percentile means that 30 percent of 3-month-old babies weigh less and 70 percent weigh more. If the percentile were 60, then 60 percent weigh less and 40 percent weigh more. The fact that the first baby is a little smaller and the second a little bigger than average is not a problem, since humans vary on every dimension. Only one baby in a 100 is exactly average, at the 50th percentile.

For any baby, however, an early sign of trouble occurs when a percentile moves 20 percent or more, either up or down. If an average baby suddenly grows more slowly, that could be the first sign of a medical condition called failure to thrive. If weight gain is accelerated, as when a baby at the 30th percentile is at the 60th percentile a month later, that may signal later obesity.

A dramatic shift in percentile in either direction was once blamed solely on parents. For small babies, it was thought that parents made feeding stressful, leading to “nonorganic failure to thrive.” Now dozens of medical conditions have been discovered that cause failure to thrive. Thus, organic causes may impede growth. Pediatricians consider it “outmoded” to blame parents (Jaffe, 2011, p. 100).

Sleep

Throughout childhood, regular and ample sleep correlates with normal brain maturation, learning, emotional regulation, academic success, and psychological adjustment (Maski & Kothare, 2013). Lifelong, sleep deprivation can cause poor health, and vice versa. As with many health habits, sleep patterns begin in the first year.

139

Same Boy, Much Changed All three photos show Conor: first at 3 months, then at 12 months, and finally at 24 months. Note the rapid growth in the first two years, especially apparent in the changing proportions of the head compared to the body and legs.

Newborns spend most of their time sleeping, about 15 to 17 hours a day. Hours of sleep decrease rapidly with maturity: The norm per day for the first 2 months is 14¼ hours; for the next 3 months, 13¼ hours; for 6 to 17 months, 12¾ hours. Remember that norms are simply averages. Among every 20 newborns in the United States, parents report that one sleeps only nine hours per day and one sleeps 19 hours (Sadeh et al., 2009) (see Figure 5.2).

FIGURE 5.2
Good Night, Moon Average sleep per 24-hour period is given in percentiles because there is much variation in how many hours a young child normally sleeps. Other charts from this study show nighttime sleep and daytime napping. Most 1-year-olds sleep about 10 hours a night, with about 2 hours of napping, but some sleep much less. By age 3, about 10 percent have given up naps altogether. Note that these data are drawn from reports by U.S. parents, based on an Internet questionnaire. Actual sleep monitors or reports by a more diverse group of parents would show even more variation.

Cultural differences are apparent. By age 2, the typical toddler in New Zealand sleeps 15 percent more than the typical Japanese one, 13.3 hours a day compared to 11.6 (Sadeh et al., 2010). Everywhere, full-term newborns sleep more than preterm newborns, who need to eat every two hours.

Infants also vary in how long they sleep at a stretch. If “sleeping through the night” means sleeping from midnight to 5 a.m., half of all babies sleep through the night at least once by 3 months, but if a night is from 10 p.m. to 6 a.m., some 1-year-olds still do not sleep all night long (Russell et al., 2013).

Over the first months, the relative amount of time spent in each type or stage of sleep changes. Babies born preterm may always seem to be dozing. Full-term newborns dream a lot; about half their sleep is REM sleep (rapid eye movement sleep), with flickering eyes and rapid brain waves. That indicates dreaming. REM sleep declines over the early weeks, as does “transitional sleep,” the dozing, half-awake stage. At 3 or 4 months, quiet sleep (also called slow-wave sleep) increases markedly.

140

By about 3 months, all the various states of waking and sleeping become more evident. Thus, although newborns often seem half asleep, neither in deep sleep nor wide awake, by 3 months most babies have periods of alertness and periods of deep sleep (when noises do not rouse them).

Sleep varies not only because of biology (age and genes) but also because of caregiver actions. Babies who are fed cow’s milk and cereal sleep longer and more soundly—easier for parents but not good for the baby. Social environment matters more directly: If parents respond to predawn cries with food and play, babies learn to wake up early and often, night after night, which may not be good for anyone (Sadeh et al., 2009).

Insufficient sleep may become a serious problem for parents as well as for infants, because “[p]arents are rarely well-prepared for the degree of sleep disruption a newborn infant engenders, and many have unrealistic expectations about the first few postnatal months.” As a result many parents become “desperate” and institute patterns that they may later regret. (Russell et al., 2013, p. 68). This is more common in first-time parents; sleep problems are less often reported for later-born children.

opposing perspectives

Where Should Babies Sleep?

Traditionally, most middle-class U.S. infants slept in cribs in their own rooms; it was feared that they would be traumatized if their parents had sex. By contrast, most infants in Asia, Africa, and Latin America slept near their parents, a practice called co-sleeping, and sometimes in their parents’ bed, called bed-sharing. In those cultures, nighttime parent–child separation was considered cruel.

Even today, at baby’s bedtime, Asian and African mothers worry more about separation, whereas European and North American mothers worry more about privacy. A survey found that parents act on these fears: The extremes were 82 percent of Vietnam babies co-sleeping compared with 6 percent in New Zealand (Mindell et al., 2010) (see Figure 5.3). Cohort is also significant. In the United States, bed-sharing doubled from 1993 to 2010, from 6.5 percent to 13.5 percent (Colson et al., 2013).

This difference in practice may seem related to income since low-SES families are less likely to have an extra room and women with less education are more likely to sleep beside their baby (Colson et al., 2013). But even wealthy Japanese families often co-sleep. By contrast, many low-income North American families find a separate bedroom for their children. Co-sleeping results from culture and custom, not merely income, which makes it a difficult practice to change (Ball & Volpe, 2013).

FIGURE 5.3
Awake at Night Why the disparity between Asian and non-Asian rates of co-sleeping? It may be that Western parents use a variety of gadgets and objects—monitors, night lights, pacifiers, cuddle cloths, sound machines—to accomplish the same things Asian parents do by having their infant beside them.

141

The argument for bed-sharing is that the parents can quickly respond to a hungry or frightened baby without needing to get up to feed or comfort their infant. Breast-feeding, often done every hour or two at first, is less exhausting when the mother can stay in bed as she nurses.

Yet the argument against bed-sharing rests on a chilling statistic: Sudden infant death is twice as likely when babies sleep beside their parents (Vennemann et al., 2012). (Sudden infant death syndrome is discussed at the end of this chapter.) Many young parents occasionally go to sleep after drinking or drugging. If their baby is beside them, bed-sharing (not merely co-sleeping) is dangerous.

Since many ethnic groups co-sleep as a cultural practice, instead of arguing against it, experts seek ways to make it safe (Ball & Volpe, 2013). One innovation is the creation of a “co-sleeper” (an attachment to the parents’ bed), which avoids soft quilts or rollover danger.

Infant at Risk? Sleeping in the parents’ bed is a risk factor for SIDS in the United States, but don’t worry about this Japanese girl. In Japan, 97 percent of infants sleep next to their parents, yet infant mortality is only 3 per 1,000—compared with 7 per 1,000 in the United States. Is this bed, or this mother, or this sleeping position protective?

One reason for opposite practices is that adults are affected by their own early experiences. This phenomenon is called ghosts in the nursery because new parents bring decades-old memories into the bedrooms of their children. Those ghosts can encourage either co-sleeping or separate rooms.

For example, compared with Israeli adults who, as infants, had slept near their parents, those who had slept communally with other infants (as sometimes occurred on kibbutzim) were more likely to interpret their own infants’ nighttime cries as distress, requiring comfort (Tikotzky et al., 2010). That is how a ghost affects current behavior: If parents think their crying babies are frightened, lonely, and distressed, they want to respond. Quick responses are easier with co-sleeping.

But remember that infants learn from experience. If babies become accustomed to bed-sharing, they will crawl into their parents’ bed long past infancy. Parents might lose sleep for years because they wanted more sleep when their babies were small.

Developmentalists hesitate to declare either co-sleeping or separate bedrooms best because the issue is “tricky and complex” (Gettler & McKenna, 2010, p. 77). Sleeping alone may encourage independence—a trait appreciated in some cultures, abhorred in others. Past experiences (ghosts in the nursery) affect us all: Should some ghosts be welcomed and others banned?

An Internet study of more than 5,000 North American children under age 3 found that, according to their parents, sleep was a problem for 25 percent (Sadeh et al., 2009). Of course, parents are more troubled by their baby’s difficulty going to sleep, or staying asleep, than the baby is. This does not render sleep difficulties insignificant; overtired parents are less patient and responsive.

Parents will be frustrated if they expect their infant to conform to the parents’ sleep–wake schedule because infant brain patterns and digestion do not allow young babies to sleep quietly all night long. Maternal depression and family dysfunction are more common when infants wake up frequently at night (Piteo et al., 2013).

Especially for New Parents You are aware of cultural differences in sleeping practices, which raises a very practical issue: Should your newborn sleep in bed with you?

From the psychological and cultural perspectives, babies can sleep anywhere as long as the parents can hear them if they cry. The main consideration is safety: Infants should not sleep on a mattress that is too soft, nor beside an adult who is drunk or drugged. Otherwise, each family should decide for itself.

Parent reactions shape infant sleep patterns, which in turn affect the parents (Sadeh et al., 2010). Ideally, mutual adaptations allow everyone’s needs to be met, but, as the Opposing Perspectives feature explains, this is more controversial than it seems.

142

SUMMING UP   Birthweight doubles, triples, and quadruples by 4 months, 12 months, and 24 months, respectively. Height increases by about a foot (about 30 centimeters) in the first two years. Such norms are useful as general guidelines, but personal percentile rankings over time are more telling. They indicate whether a particular infant’s brain and body are growing appropriately. With maturation, sleep becomes regular, dreaming becomes less common, and distinct sleep–wake patterns develop. The youngest infants sleep more hours in total but for less time at a stretch; by age 1, most babies sleep longer at night, with a nap or two during the day. Cultural and caregiving practices influence norms, schedules, and expectations.

WHAT HAVE YOU LEARNED?

  1. Question 5.1

    uAvQJ99KnVDUG0Ft7b/Y6WARCjg0QN2LsbWSUfU39AIlZnKtofDJb1UvbkgqCyYVE0ZsXrbkMJ9/N0vV2+T0lYaptlA/qZ4MZE3r7gHH5EY=
    Birthweight typically doubles by 4 months and triples by a year. On average, a 7–pound newborn will be 21 pounds at 12 months (9,525 grams, up from 3,400 grams at birth). Height increases, too. A typical baby grows 10 inches (24 centimeters) in a year.

  2. Question 5.2

    v2a9oeEdTUmKwD32xJ5KESqbs+rgzkQm4s2QPsUHRZ7yTPR3YS9IRMT8sOIjoAs+IND5ggesFSJTfQvx7JYlb+0VdpVltjeRlO8YgcdEAl/HmkkiT1Vccq3eGA1qJjqNEtJATSryIxYo1NAEGTwgKjqzVb4UtMudJvjldksZcj4=
    At each well–baby checkup (monthly at first), growth is compared to the baby's previous numbers. Often, measurements are expressed as a percentile, from 0 to 100, that indicates where an individual ranks on a particular measure. Percentiles are often used for school achievement; here they are used to indicate how an infant's growth compares to other babies of the same age. Thus, a 3–month–old's weight at the 20th percentile means that 20 percent of 3–month–old babies weigh less and 80 percent weigh more. If the percentile were 60, then 60 percent weigh less and 40 percent weigh more. The fact that the first baby is a little smaller and the second a little bigger than average is not a problem, since humans vary on every dimension. Only one baby in 100 is exactly average at the 50th percentile.

  3. Question 5.3

    oW2dyGH7iVmwjZ1bnHkbXl7J2VwYBJ/pd7OhniuQb5xe1sbU6FX2GA2X6RxkDtAELLHCtQ==
    Newborns spend most of their time sleeping, about 15 to 17 hours a day. Hours of sleep decrease rapidly with maturity. The norm per day for the first 2 months is 14¼ hours; for the next 3 months, 13¼ hours; for 6 to 17 months, 12¾ hours. However, norms are simply averages. Among every 20 newborns in the United States, parents report that one sleeps only nine hours per day and one sleeps 19 hours. Full–term newborns dream a lot; about half their sleep is REM sleep (rapid eye movement sleep), with flickering eyes and rapid brain waves. That indicates dreaming. REM sleep declines over the early weeks, as does “transitional sleep,” the dozing, half–awake stage. At 3 or 4 months, quiet sleep (also called slow–wave sleep) increases markedly.

  4. Question 5.4

    9VWZSRsBzBQnIyVlBnCd1cj6YwjT8Um1gWuRUwOXJ3HZVSRUDMpNN5J9KjSS2LW0+qB5N6PmUz1LokxS
    Hours of sleep decrease rapidly with maturity. The norm per day for the first two months is 14¼ hours; for the next three months, 13¼ hours; for six to 17 months, 12¾ hours.