ENVIRONMENTAL-FACTORS INFLUENCING GROWTH AND PUBERTAL DEVELOPMENT

Postnatal growth is based on hereditary signals and environmental fact ors in a complex regulatory network. Each factor must be in an optimal state for normal growth of the child. Fetal conditions may also have consequences on postnatal height. Intrauterine growth retardation can be recovered postnatally, although postnatal growth remains depressed in about one-third of cases. After birth, the environment may exert ei ther a positive or negative effect on growth. In underdeveloped countr ies, malnutrition plays a major role in inhibiting the growth process. Children from families of higher socioeconomic classes are taller tha n their coevals in the lower socioeconomic groups. Urbanization also h as a positive effect on growth. Better child care is supported by suff icient food supply, appropriate health and sanitation services, and a higher level of education. Over the last century, these factors have i nduced a taller stature and a more rapid maturity in Europe, North Ame rica, and Australia; a phenomenon which has been referred to as ''the secular trend'' in growth. Recently, a secular trend has also been rep orted in some developing countries. Although urbanization in general a ppears to be associated with better conditions of living, this is not the case in the slums of South America or in Africa where rural childr en are better off than children living in the poor cities. This paper describes in more detail the different hereditary and environmental fa ctors that act during the fetal period and postnatally, and which play a role in human growth and pubertal development.