CHAPTER 2. HEALTHY CHILD

PERIODS OF CHILDHOOD. ANATOMICAL AND PHYSIOLOGICAL FEATURES

Concepts of age and age periodization in pediatric practice

Childhood is the longest period of human development, comprising at least 20% of the physiological life expectancy. The United Nations Convention on the Rights of the Child defines childhood as the age span ranging from birth to 18 years (in the USA - up to 21 years old).

Unlike adults, children need to be followed up by health care specialists much more often and, since the duration of inter-evaluation periods is related to the age of the child (table 2.1), the younger the child, the more often he or she is brought to see the doctor.

Table 2.1. Time intervals for child status monitoring

• Gestational age (Lat. gestatio, bearing) is the age of the embryo and fetus from the moment of fertilization.

• According to the rules adopted either by WHO and by Russian Government, every product of conception that was born with a body weight of 500 g or more is considered a child of about 20-22 weeks gestation.

• Postconceptual age should be taken into consideration in preterm infants. It includes the sum of gestational and chronological (calendar) ages (for example: a baby was born at the 27th week of gestation, now he is 4 weeks old, i.e. his post-conceptual age is 31 weeks).

Each period of childhood has special morphological, physiological, and psychological features, therefore, the process of human ontogenesis may be divided into various periods or stages of development. The three most important periods are: the preparatory phase, intrauterine development and postnatal phase, or childhood itself (table 2.2).

Table 2.2. Extraand intrauterine stages. Periods of human development