The head circumference growth rate during the first year is approximately 4⁄10 inch (1 cm) per month. Usually the posterior fontanel closes by 2 to 3 months of age, whereas the larger anterior fontanel may remain open until 18 months. Head circumference and fontanel measurements indicate brain growth and are obtained, along with height and weight, at each well-baby visit. Chapter 33 discusses growth-rate monitoring throughout infancy.

In addition to height and weight, organ systems grow and mature rapidly in the infant. Although body systems are developing rapidly, the infant’s organs differ from those of older children and adults in both structure and function. These differences place the infant at risk for problems that might not be expected in older individuals. For example, immature respiratory and immune systems place the infant at risk for a variety of infections, whereas an immature renal system increases risk for fluid and electrolyte imbalances. Knowledge of these differences provides the nurse with important rationales on which to base anticipatory guidance and specific nursing interventions.

During the first few months after birth, muscle growth and weight gain allow for increased control of reflexes and more purposeful movement. At 1 month, movement occurs in a random fashion, with the fists tightly clenched. Because the neck musculature is weak, and the head is large, infants can lift their heads only briefly. By 2 to 3 months, infants can lift their heads 90 degrees from a prone position and can hold them steadily erect in a sitting position. During this time, active grasping gradually replaces reflexive grasping and increases in frequency as eye-hand coordination improves (see Table 6-1).

The Moro, tonic neck, and rooting reflexes disappear at approximately 3 to 4 months. These primitive reflexes, which are controlled by the midbrain, probably disappear because they are suppressed by growing cortical layers. Head control steadily increases during the third month. By the fourth month, the head remains in a straight line with the body when the infant is pulled to a sitting position. Most infants play with their feet by 4 to 5 months, drawing them up to suck on their toes. Parents need anticipatory guidance about ways to prevent unintentional injury by “baby-proofing” their homes before each motor development milestone is reached.

Cognitive development during the first 2 years of life begins with a profound state of egocentrism. Egocentrism is the child’s complete self-absorption and the inability to view the world from anyone else’s vantage point (Piaget, 1952). As infants’ cognitive capacities expand, they become increasingly aware of the outside world and their separateness from it. Gradually, with maturation and experience, they become capable of differentiating themselves from others and their surroundings.

According to Piaget’s theory (1952), cognitive development occurs in stages or periods (see Chapter 5) as described in the following discussion. Infancy is included in the sensorimotor stage (birth to 2 years), during which infants experience the world through their senses and their attempts to control the environment. Learning activities progress from simple reflex behavior to trial-and-error experiments.

During the first month of life, infants are in the first substage, reflex activity, of the sensorimotor period. In this substage, behavior such as grasping, sucking, or looking is dominated by reflexes. Piaget believed that infants organize their activity, survive, and adapt to their world by the use of reflexes.

Primary circular reactions dominate the second substage, occurring from age 1 to 4 months. During this substage, reflexes become more organized, and new schemata are acquired, usually centering on the infant’s body. Sensual activities such as sucking and kicking become less reflexive and more controlled and are repeated because of the stimulation they provide. The baby also begins to recognize objects, especially those that bring pleasure, such as the breast or bottle.

During the third substage, or the stage of secondary circular reactions, infants perform actions that are more oriented toward the world outside their own bodies. The 4- to 8-month-old infant in this substage begins to play with objects in the external environment, such as a rattle or stuffed toy. The infant’s actions are labeled secondary because they are intentional (repeated because of the response that is elicited). For example, a baby in this substage intentionally shakes a rattle to hear the sound.

By age 8 to 12 months, infants in the fourth substage, coordination of secondary schemata, begin to relate to objects as if they realize that the objects exist even when they are out of sight. This awareness is referred to as object permanence and is illustrated by a 9-month-old infant seeking a toy after it is hidden under a pillow. In contrast, 6-month-olds can follow the path of a toy that is dropped in front of them; however, they will not look for the dropped toy or protest its disappearance until they are older and have developed the concept of object permanence.

Infants in the fourth substage solve problems differently from how they solve problems in earlier substages. Rather than randomly selecting approaches to problems, they choose actions that were successful in the past. This tendency suggests that they remember and can perform some mental processing. They seem to be able to identify simple causal relationships, and they show definite intentionality. For example, when an 11-month-old child sees a toy that is beyond reach, the child uses the blanket that it is resting on to pull it closer (Flavell, 1964; Piaget, 1952).

Cognitive development in the infant parallels motor development. It appears that motor activity is necessary for cognitive development and that cognitive development is based on interaction with the environment, not simply maturation. Infancy is the period when the child lays the foundation for later cognitive functioning. Nurses can promote infants’ cognitive development by encouraging parents to interact with their infants and provide them with novel, interesting stimuli. At the same time, parents should maintain familiar, routine experiences through which their infants can develop a sense of security about the world. Within this type of environment, infants will thrive and learn.

The acquisition of language has its roots in infancy as the child becomes increasingly intrigued with sound, begins to realize that words have meaning, and eventually uses simple sounds to communicate (Box 6-1). Although young infants probably understand tones and inflections of voice rather than words themselves, it is not long before repetition and practice of sounds enable them to understand and communicate with words. Infants can understand more than they can express.

The social smile develops early in the infant, usually by 3 to 5 weeks of age (Figure 6-1). This powerful communication tool helps to foster attachment and demonstrates that the infant can differentiate between people and objects within the environment. The infant who does not display a social smile by 8 to 12 weeks of age needs further evaluation and close follow-up because of the possibility of developmental delay.

Vocalization, or speech, does not appear to be reflexive but rather is a relatively high-level activity similar to conversation. Parents usually elicit vocalization in infants better than other adults can. Language includes understanding word meanings, how to combine words into meaningful sentences and phrases, and social use of conversation. The development of both speech and language can be influenced by environmental cues, such as structures unique to a native language, physical disorders, hearing loss, cognitive impairment, autism spectrum disorders, or learning disabilities such as dyslexia (Schum, 2007).

Although there is great variability, most children begin to make nonmeaningful sounds, such as “ma,” “da,” or “ah,” by 4 to 6 months. The sounds become more meaningful and specific by 9 to 15 months, and by age 1 year the child usually has a vocabulary of several words, such as “mama,” “dada,” and “bye-bye.” Infants who have older siblings or who are raised in verbally rich environments sometimes meet these developmental milestones earlier than other infants.

Most experts agree that infancy is a crucial period during which children develop the foundation of their personalities and their sense of self. According to Erikson’s theory of psychosocial development (1963), infants struggle to establish a sense of basic trust rather than a sense of basic mistrust in their world, their caregivers, and themselves. If provided with consistent, satisfying experiences delivered in a timely manner, infants come to rely on the fact that their needs will be met and that, in turn, they will be able to tolerate some degree of frustration and discomfort until those needs are met. This sense of confidence is an early form of trust and provides the foundation for a healthy personality.

Conversely, if infants’ needs are ignored or met in a consistently haphazard, inadequate manner, they have no reason to believe that their needs will be met or that their environment is a safe, secure place. According to Erikson, without consistent satisfaction of needs, the individual develops a basic sense of suspicion or mistrust (Erikson, 1963).

Parallel to this viewpoint is Freudian theory, which regards infancy as the oral stage (Freud, 1974). The mouth is the major focus during this stage. Observation of infants for a few minutes shows that most of their behavior centers on their mouths. Sensory stimulation and pleasure, as well as nourishment, are experienced through their mouths. Sucking is an adaptive behavior that provides comfort and satisfaction while enabling infants to experience and explore their world. Later in infancy, as teething progresses, the mouth becomes an effective tool for aggressive behavior (see Chapter 7).

Nurses play an important role in health promotion and disease prevention related to immunization. Nursing responsibilities include assessing current immunization status, removing barriers to receiving immunizations, tracking immunization records, providing parent education, and recognizing contraindications to the receipt of vaccines. Chapter 5 provides detailed information regarding immunizations and their schedule.