Paediatrics: Normal growth

Normal growth

Normal human growth can be divided into two distinct phases: prenatal (foetal) and postnatal.

Prenatal/foetal growth

This is the fastest period of growth, accounting for around 30% of eventual height. Factors that determine growth during this period include maternal size, maternal nutrition, and intrauterine environment. Hormonal factors such as insulin, insulin-like growth factor (IGF)–II, and human placental lactogen are important regulators of growth during this period.

Postnatal growth

This is classically divided into three overlapping periods.

Infantile period

From birth to 18–24mths of age. Rapid but decelerating growth rate (growth velocity range: 22–8cm/yr). Growth is largely under nutritional regulation during this period. Some infants (15–20%) may show significant catch-up or catch-down in length and weight. By age 2yrs, height is more predictive of final adult height than at birth.

Childhood period

From age 2yrs until onset of puberty. Characterized by a slow, steady growth velocity (range 8–5cm/yr). Growth is primarily dependent on growth hormone (GH), provided there is adequate nutrition and health.

Puberty

Growth during this period is dependent on growth hormone (GH) and the actions of sex steroid hormones (testosterone and oestrogen). This combination induces the characteristic ‘growth spurt’ of puberty. In both males and females, oestrogen induces the maturation of the epiphyseal growth centres of the bones, eventually resulting in fusion of the growth plates, the cessation of linear growth, and the attainment of final height.

Sex differences in growth during puberty

The onset of the pubertal growth spurt is earlier in females compared with males. Females are therefore, on average, taller than males between the ages of 10 and 13yrs. In males, the pubertal growth spurt is later in onset and greater in magnitude. As a result males are, on average, 12–13cm taller than females at final height.