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The First Year
The prenatal period and the 1st yr of life provide the platform for remarkable growth and development, setting the trajectory for a child's life. Neural plasticity , the ability of the brain to be shaped by experience, both positive and negative, is at its peak. Total brain volume doubles in the 1st yr of life and increases by an additional 15% over the 2nd yr. Total brain volume at age 1 mo is approximately 36% of adult volume but by age 1 yr is approximately 72% (83% by 2 yr) ( Fig. 22.1 ).
Scatterplots showing brain growth in the 1st 2 yr of life.
A, Total brain volume by age at scan. B, Cortical hemispheres. C, Cerebellum. D, Subcortical region and brainstem.
(From Knickmeyer RC, Gouttard S, Kang C, et al: A structural MRI study of human brain development from birth to 2 years, J Neurosci 28(47):12176–12182, 2008.)
The acquisition of seemingly “simple” skills, such as swallowing, reflect a series of intricate and highly coordinated processes involving multiple levels of neural control distributed among several physiologic systems whose nature and relationships mature throughout the 1st yr of life. Substantial learning of the basic tools of language (phonology, word segmentation) occurs during infancy. Speech processing in older individuals requires defined and precise neuronal networks; the infant brain possesses a structural and functional organization similar to that of adults, suggesting that structural neurologic processing of speech may guide infants to discover the properties of their native language. Myelination of the cortex begins at 7-8 mo gestation and continues into adolescence and young adulthood. It proceeds posterior to anterior, allowing progressive maturation of sensory, motor, and finally associative pathways. Given the importance of iron, cholesterol, and other nutrients in myelination, adequate stores throughout infancy are critical (see Chapter 56 ). Insufficient interactions with caregivers or the wider environment may alter experience-dependent processes that are critical to brain structure development and function during infancy. Although for some processes, subsequent stimulation may allow catch-up, as the periods of plasticity close during the rapid developmental changes occurring in infancy, more permanent deficits may result.
The infant acquires new competences in all developmental domains. The concept of developmental trajectories recognizes that complex skills build on simpler ones; it is also important to realize how development in each domain affects functioning in all the others. All growth parameters should be plotted using the World Health Organization charts, which show how children from birth through 72 mo “should” grow under optimal circumstances (see Chapter 23 , Figs. 23.1 and 23.2 ). Table 22.1 presents an overview of key milestones by domain; Table 22.2 presents similar information arranged by age. Table 22.3 presents age at time of x-ray appearance of centers of ossification. Parents often seek information about “normal development” during this period and should be directed to reliable sources, including the American Academy of Pediatrics website ( healthychildren.org ).
Table 22.1
Developmental Milestones in 1st 2 Yr of Life
| MILESTONE | AVERAGE AGE OF ATTAINMENT (MO) | DEVELOPMENTAL IMPLICATIONS |
|---|---|---|
| GROSS MOTOR | ||
| Holds head steady while sitting | 2 | Allows more visual interaction |
| Pulls to sit, with no head lag | 3 | Muscle tone |
| Brings hands together in midline | 3 | Self-discovery of hands |
| Asymmetric tonic neck reflex gone | 4 | Can inspect hands in midline |
| Sits without support | 6 | Increasing exploration |
| Rolls back to stomach | 6.5 | Truncal flexion, risk of falls |
| Walks alone | 12 | Exploration, control of proximity to parents |
| Runs | 16 | Supervision more difficult |
| FINE MOTOR | ||
| Grasps rattle | 3.5 | Object use |
| Reaches for objects | 4 | Visuomotor coordination |
| Palmar grasp gone | 4 | Voluntary release |
| Transfers object hand to hand | 5.5 | Comparison of objects |
| Thumb-finger grasp | 8 | Able to explore small objects |
| Turns pages of book | 12 | Increasing autonomy during book time |
| Scribbles | 13 | Visuomotor coordination |
| Builds tower of 2 cubes | 15 | Uses objects in combination |
| Builds tower of 6 cubes | 22 | Requires visual, gross, and fine motor coordination |
| COMMUNICATION AND LANGUAGE | ||
| Smiles in response to face, voice | 1.5 | More active social participant |
| Monosyllabic babble | 6 | Experimentation with sound, tactile sense |
| Inhibits to “no” | 7 | Response to tone (nonverbal) |
| Follows 1-step command with gesture | 7 | Nonverbal communication |
| Follows 1-step command without gesture | 10 | Verbal receptive language (e.g., “Give it to me”) |
| Says “mama” or “dada” | 10 | Expressive language |
| Points to objects | 10 | Interactive communication |
| Speaks first real word | 12 | Beginning of labeling |
| Speaks 4-6 words | 15 | Acquisition of object and personal names |
| Speaks 10-15 words | 18 | Acquisition of object and personal names |
| Speaks 2-word sentences (e.g., “Mommy shoe”) | 19 | Beginning grammatization, corresponds with 50-word vocabulary |
| COGNITIVE | ||
| Stares momentarily at spot where object disappeared | 2 | Lack of object permanence (out of sight, out of mind; e.g., yarn ball dropped) |
| Stares at own hand | 4 | Self-discovery, cause and effect |
| Bangs 2 cubes | 8 | Active comparison of objects |
| Uncovers toy (after seeing it hidden) | 8 | Object permanence |
| Egocentric symbolic play (e.g., pretends to drink from cup) | 12 | Beginning symbolic thought |
| Uses stick to reach toy | 17 | Able to link actions to solve problems |
| Pretend play with doll (e.g., gives doll bottle) | 17 | Symbolic thought |
Table 22.2
Emerging Patterns of Behavior During the 1st Yr of Life *
Data from Knobloch H, Stevens F, Malone AF: Manual of developmental diagnosis, Hagerstown, MD, 1980, Harper & Row.
| NEONATAL PERIOD (1ST 4 WK) | |
| Prone: | Lies in flexed attitude; turns head from side to side; head sags on ventral suspension |
| Supine: | Generally flexed and a little stiff |
| Visual: | May fixate face on light in line of vision; doll's eye movement (oculocephalic reflex) of eyes on turning of the body |
| Reflex: | Moro response active; stepping and placing reflexes; grasp reflex active |
| Social: | Visual preference for human face |
| AT 1 MO | |
| Prone: | Legs more extended; holds chin up; turns head; head lifted momentarily to plane of body on ventral suspension |
| Supine: | Tonic neck posture predominates; supple and relaxed; head lags when pulled to sitting position |
| Visual: | Watches person; follows moving object |
| Social: | Body movements in cadence with voice of other in social contact; beginning to smile |
| AT 2 MO | |
| Prone: | Raises head slightly farther; head sustained in plane of body on ventral suspension |
| Supine: | Tonic neck posture predominates; head lags when pulled to sitting position |
| Visual: | Follows moving object 180 degrees |
| Social: | Smiles on social contact; listens to voice and coos |
| AT 3 MO | |
| Prone: | Lifts head and chest with arms extended; head above plane of body on ventral suspension |
| Supine: | Tonic neck posture predominates; reaches toward and misses objects; waves at toy |
| Sitting: | Head lag partially compensated when pulled to sitting position; early head control with bobbing motion; back rounded |
| Reflex: | Typical Moro response has not persisted; makes defensive movements or selective withdrawal reactions |
| Social: | Sustained social contact; listens to music; says “aah, ngah” |
| AT 4 MO | |
| Prone: | Lifts head and chest, with head in approximately vertical axis; legs extended |
| Supine: | Symmetric posture predominates, hands in midline; reaches and grasps objects and brings them to mouth |
| Sitting: | No head lag when pulled to sitting position; head steady, tipped forward; enjoys sitting with full truncal support |
| Standing: | When held erect, pushes with feet |
| Adaptive: | Sees raisin, but makes no move to reach for it |
| Social: | Laughs out loud; may show displeasure if social contact is broken; excited at sight of food |
| AT 7 MO | |
| Prone: | Rolls over; pivots; crawls or creep-crawls (Knobloch) |
| Supine: | Lifts head; rolls over; squirms |
| Sitting: | Sits briefly, with support of pelvis; leans forward on hands; back rounded |
| Standing: | May support most of weight; bounces actively |
| Adaptive: | Reaches out for and grasps large object; transfers objects from hand to hand; grasp uses radial palm; rakes at raisin |
| Language: | Forms polysyllabic vowel sounds |
| Social: | Prefers mother; babbles; enjoys mirror; responds to changes in emotional content of social contact |
| AT 10 MO | |
| Sitting: | Sits up alone and indefinitely without support, with back straight |
| Standing: | Pulls to standing position; “cruises” or walks holding on to furniture |
| Motor: | Creeps or crawls |
| Adaptive: | Grasps objects with thumb and forefinger; pokes at things with forefinger; picks up pellet with assisted pincer movement; uncovers hidden toy; attempts to retrieve dropped object; releases object grasped by other person |
| Language: | Repetitive consonant sounds (“mama,” “dada”) |
| Social: | Responds to sound of name; plays peek-a-boo or pat-a-cake; waves bye-bye |
| AT 1 YR | |
| Motor: | Walks with one hand held; rises independently, takes several steps (Knobloch) |
| Adaptive: | Picks up raisin with unassisted pincer movement of forefinger and thumb; releases object to other person on request or gesture |
| Language: | Says a few words besides “mama,” “dada” |
| Social: | Plays simple ball game; makes postural adjustment to dressing |
* Data are derived from those of Gesell (as revised by Knobloch), Shirley, Provence, Wolf, Bailey, and others.
Table 22.3
Time of Radiographic Appearance of Centers of Ossification in Infancy and Childhood
The norms present a composite of published data from the Fels Research Institute, Yellow Springs, OH (Pyle SI, Sontag L: AJR Am J Roentgenol 49:102, 1943), and unpublished data from the Brush Foundation, Case Western Reserve University, Cleveland, OH, and the Harvard School of Public Health, Boston, MA. Compiled by Lieb, Buehl, and Pyle.
| BOYS—AGE AT APPEARANCE * | BONES AND EPIPHYSEAL CENTERS | GIRLS—AGE AT APPEARANCE * |
|---|---|---|
| HUMERUS, HEAD | ||
| 3 wk | 3 wk | |
| CARPAL BONES | ||
| 2 mo ± 2 mo | Capitate | 2 mo ± 2 mo |
| 3 mo ± 2 mo | Hamate | 2 mo ± 2 mo |
| 30 mo ± 16 mo | Triangular † | 21 mo ± 14 mo |
| 42 mo ± 19 mo | Lunate † | 34 mo ± 13 mo |
| 67 mo ± 19 mo | Trapezium † | 47 mo ± 14 mo |
| 69 mo ± 15 mo | Trapezoid † | 49 mo ± 12 mo |
| 66 mo ± 15 mo | Scaphoid † | 51 mo ± 12 mo |
| No standards available | Pisiform † | No standards available |
| METACARPAL BONES | ||
| 18 mo ± 5 mo | II | 12 mo ± 3 mo |
| 20 mo ± 5 mo | III | 13 mo ± 3 mo |
| 23 mo ± 6 mo | IV | 15 mo ± 4 mo |
| 26 mo ± 7 mo | V | 16 mo ± 5 mo |
| 32 mo ± 9 mo | I | 18 mo ± 5 mo |
| FINGERS (EPIPHYSES) | ||
| 16 mo ± 4 mo | Proximal phalanx, 3rd finger | 10 mo ± 3 mo |
| 16 mo ± 4 mo | Proximal phalanx, 2nd finger | 11 mo ± 3 mo |
| 17 mo ± 5 mo | Proximal phalanx, 4th finger | 11 mo ± 3 mo |
| 19 mo ± 7 mo | Distal phalanx, 1st finger | 12 mo ± 4 mo |
| 21 mo ± 5 mo | Proximal phalanx, 5th finger | 14 mo ± 4 mo |
| 24 mo ± 6 mo | Middle phalanx, 3rd finger | 15 mo ± 5 mo |
| 24 mo ± 6 mo | Middle phalanx, 4th finger | 15 mo ± 5 mo |
| 26 mo ± 6 mo | Middle phalanx, 2nd finger | 16 mo ± 5 mo |
| 28 mo ± 6 mo | Distal phalanx, 3rd finger | 18 mo ± 4 mo |
| 28 mo ± 6 mo | Distal phalanx, 4th finger | 18 mo ± 5 mo |
| 32 mo ± 7 mo | Proximal phalanx, 1st finger | 20 mo ± 5 mo |
| 37 mo ± 9 mo | Distal phalanx, 5th finger | 23 mo ± 6 mo |
| 37 mo ± 8 mo | Distal phalanx, 2nd finger | 23 mo ± 6 mo |
| 39 mo ± 10 mo | Middle phalanx, 5th finger | 22 mo ± 7 mo |
| 152 mo ± 18 mo | Sesamoid (adductor pollicis) | 121 mo ± 13 mo |
| HIP AND KNEE | ||
| Usually present at birth | Femur, distal | Usually present at birth |
| Usually present at birth | Tibia, proximal | Usually present at birth |
| 4 mo ± 2 mo | Femur, head | 4 mo ± 2 mo |
| 46 mo ± 11 mo | Patella | 29 mo ± 7 mo |
| FOOT AND ANKLE ‡ | ||
Values represent mean ± standard deviation, when applicable.
† Except for the capitate and hamate bones, the variability of carpal centers is too great to make them very useful clinically.
‡ Standards for the foot are available, but normal variation is wide, including some familial variants, so this area is of little clinical use.
Age 0-2 Months
In the full-term infant, myelination is present by the time of birth in the dorsal brainstem, cerebellar peduncles, and posterior limb of the internal capsule. The cerebellar white matter acquires myelin by 1 mo of age and is well myelinated by 3 mo. The subcortical white matter of the parietal, posterior frontal, temporal, and calcarine cortex is partially myelinated by 3 mo of age. In this period the infant experiences tremendous growth. Physiologic changes allow the establishment of effective feeding routines and a predictable sleep–wake cycle. The social interactions that occur as parents and infants accomplish these tasks lay the foundation for cognitive and emotional development.
Physical Development
A newborn's weight may initially decrease 10% (vaginal delivery) to 12% (cesarean section) below birthweight in the 1st wk as a result of excretion of excess extravascular fluid and limited nutritional intake. Nutrition improves as colostrum is replaced by higher-fat content breast milk, and when infants learn to latch on and suck more efficiently, and as mothers become more comfortable with feeding techniques. Infants regain or exceed birthweight by 2 wk of age and should grow at approximately 30 g (1 oz) per day during the 1st mo (see Table 27.1 ). This is the period of fastest postnatal growth. Arms are held to the sides. Limb movements consist largely of uncontrolled writhing, with apparently purposeless opening and closing of the hands. Smiling occurs involuntarily. Eye gaze, head turning, and sucking are under better control and thus can be used to demonstrate infant perception and cognition. An infant's preferential turning toward the mother's voice is evidence of recognition memory.
Six behavioral states have been described (see Chapter 21 ). Initially, sleep and wakefulness are evenly distributed throughout the 24 hr day ( Fig. 22.2 ). Neurologic maturation accounts for the consolidation of sleep into blocks of 5 or 6 hr at night, with brief awake, feeding periods. Learning also occurs; infants whose parents are consistently more interactive and stimulating during the day learn to concentrate their sleeping during the night.
Cognitive Development
Infants can differentiate among patterns, colors, and consonants. They can recognize facial expressions (smiles) as similar, even when they appear on different faces. They also can match abstract properties of stimuli, such as contour, intensity, or temporal pattern, across sensory modalities. Infants at 2 mo of age can discriminate rhythmic patterns in native vs non-native language. Infants appear to seek stimuli actively, as though satisfying an innate need to make sense of the world. These phenomena point to the integration of sensory inputs in the central nervous system. Caretaking activities provide visual, tactile, olfactory, and auditory stimuli, all of which support the development of cognition. Infants habituate to the familiar, attending less to repeated stimuli and increasing their attention to novel stimuli.
Emotional Development
The infant is dependent on the environment to meet his or her needs. The consistent availability of a trusted adult to meet the infant's urgent needs creates the conditions for secure attachment . Basic trust vs mistrust, the first of Erikson's psychosocial stages (see Chapter 18 ), depends on attachment and reciprocal maternal bonding. Crying occurs in response to stimuli that may be obvious (a soiled diaper) but are often obscure (see Chapter 22.1 ). Infants who are consistently picked up and held in response to distress cry less at 1 yr and show less aggressive behavior at 2 yr. Infants cry in response to the cry of another infant, which has been interpreted as an early sign of empathy.
Implications for Parents and Pediatricians
Success or failure in establishing feeding and sleep cycles influences parents' feelings of competence. When things go well, the parents' anxiety and ambivalence, as well as the exhaustion of the early weeks, decrease. Infant issues (e.g., colic) or familial conflict may prevent this from occurring. With physical recovery from delivery and hormonal normalization, the mild postpartum “blues” that affects many mothers passes. If the mother continues to feel sad, overwhelmed, and anxious, the possibility of moderate to severe postpartum depression, found in 10–15% of postpartum women, needs to be considered. Major depression that arises during pregnancy or in the postpartum period threatens the mother–child relationship and is a risk factor for later cognitive and behavioral problems. The pediatrician may be the first professional to encounter the depressed mother and should be instrumental in assisting her in seeking treatment (see Chapter 21 ).
Age 2-6 Months
At about age 2 mo, the emergence of voluntary (social) smiles and increasing eye contact mark a change in the parent–child relationship, heightening the parents' sense of being loved reciprocally. During the next months, an infant's range of motor and social control and cognitive engagement increases dramatically. Mutual regulation takes the form of complex social interchanges, resulting in strong mutual attachment and enjoyment. Routines are established. Parents are less fatigued.
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