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INTRODUCTION

This chapter provides an overview of typical development, identifies developmental variations, and discusses several developmental disorders. It does not cover typical development in the newborn period or adolescence (see Chapters 2 and 4, respectively). It addresses behavioral variations that reflect the spectrum of normal development, along with developmental and behavioral disorders and their treatment. The developmental principle of ongoing change and maturation is integral to the daily practice of pediatrics. The medical home is the optimal setting to understand and enhance typical development and to address variations, delays, and deviations as they may occur in the life trajectory of the child and the family.

NORMAL DEVELOPMENT

Typically developing children follow a trajectory of increasing physical size and increasing complexity of function, especially during the first 5 years of life. The child triples his or her birth weight within the first year and achieves two-thirds of his or her adult brain size by age 2½–3 years of age. The child progresses from a totally dependent infant at birth to a mobile, verbal person who can express his or her needs and desires by age 2–3 years. In the ensuing 3 years, the child further develops the capacity to interact with peers and adults, achieves considerable verbal and physical prowess, and prepares to enter the academic world of learning and socialization.

It is critical for the clinician to identify disturbances in development during these early years as there are windows of opportunity to intervene and effectively address developmental challenges.

Early developmental milestones have been recently updated by the Centers for Disease Control and Prevention (CDC) and the American Academy of Pediatrics (AAP) with the goal of providing evidence-informed guidelines for surveillance and providing clinicians with firm expectations for developmental progress. Many of the traditional milestones have been adjusted to align with the age at which most children would be expected to achieve this milestone. Milestones that coincide with health supervision visits were also included. It is important to consider the range of normal around a milestone but also to know when a clinician should consider further evaluation and intervention. These new guidelines provide surveillance recommendations and eliminate the need for a “watch and wait” mentality. The updated guidelines can be found on the CDC website referenced below. Selected milestones are included here for specific illustrations.

THE FIRST 2 YEARS

From a motor perspective, children develop in cephalocaudal and mediolateral directions. They can lift their heads with good control at 4 months, sit independently at 9 months, take first steps at 15 months, and run by 24 months. The child learning to walk has a wide-based gait at first. Next, he or she walks with legs closer together, the arms move medially, a heel-toe gait develops, and the arms swing symmetrically by 24 months.

Clinicians often focus on ...

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