Germinal: Conception to approximately 2 weeks

Embryonic: 2 to 8 weeks

Fetal: 8 to 40 weeks (birth)

A rapid growth rate and total dependency make this one of the most crucial periods in the developmental process. The relationship between maternal health and certain manifestations in the newborn emphasizes the importance of adequate prenatal care to the health and well-being of the infant.

Neonatal: Birth to 27 to 28 days

Infancy: 1 to approximately 12 months

The infancy period is one of rapid motor, cognitive, and social development. Through mutuality with the caregiver (parent), the infant establishes a basic trust in the world and the foundation for future interpersonal relationships. The critical first month of life, although part of the infancy period, is often differentiated from the remainder because of the major physical adjustments to extrauterine existence and the psychological adjustment of the parent.

Toddler: 1 to 3 years

Preschool: 3 to 6 years

This period, which extends from the time the children attain upright locomotion until they enter school, is characterized by intense activity and discovery. It is a time of marked physical and personality development. Motor development advances steadily. Children at this age acquire language and wider social relationships, learn role standards, gain self-control and mastery, develop increasing awareness of dependence and independence, and begin to develop a self-concept.

Frequently referred to as the “school age,” this period of development is one in which the child is directed away from the family group and centered around the wider world of peer relationships. There is steady advancement in physical, mental, and social development, with emphasis on developing skill competencies. Social cooperation and early moral development take on more importance with relevance for later life stages. This is a critical period in the development of the self-concept.

Prepubertal: 10 to 13 years

Adolescence: 13 to approximately 18 years

The tumultuous period of rapid maturation and change known as adolescence is considered to be a transitional period that begins at the onset of puberty and extends to the point of entry into the adult world—usually high school graduation. Biological and personality maturation are accompanied by physical and emotional turmoil, and there is redefining of the self-concept. In the late adolescent period, the young person begins to internalize all previously learned values to focus on an individual, rather than a group, identity.