Short stature is defined as a height that is 2 or more standard deviations below the mean for age and gender within a population (below the 2.5th percentile).
Growth deceleration is defined as a growth velocity that is below the 5th percentile for age and gender (e.g., <5 cm/year after the age of 5 years), or a height drop across 2 or more percentiles on the growth chart.
About 2% of all children, or more than 1 million children in the US, present with short stature. Boys come to medical attention because of short stature more frequently than girls. However, one study found that 38% of boys and 20% of girls who were referred were of normal height, the referral being due to errors in measurement, errors in plotting on the growth chart, or failure to account for the child's genetic height potential.  
In most truly short children, there is often no organic cause but rather a combination of familial (genetic) short stature and constitutional delay of growth and development. However, in a small number of children, short stature can be a manifestation of a pathologic condition (e.g., endocrinopathy, malabsorption, renal disease, inflammatory disease). In a school-based study, 14% of children who were shorter than the 3rd percentile and growing at <5 cm/year were found to have an underlying medical condition, of which 5% were endocrine in origin.1[B] Evidence Evidence
Factors determining normal growth depend on the child's age. An alteration in any of the factors can lead to growth failure. 
Prenatal growth: the major determinants of fetal growth are uterine size, placental function, maternal nutrition, insulin, insulin-like growth factors (IGFs), and IGF-binding proteins (IGFBPs).
Postnatal growth: this is characterized by an initial rapid growth rate that declines progressively, reaching a plateau of about 5 to 7 cm/year between 3 years of age until puberty. Babies born large or small for their genetic potential will "channel" to their correct percentile in their first 2 years. Growth hormone, thyroid hormones, nutrition, and insulin play major roles at this time.
Pubertal growth: immediately prior to puberty, growth usually slows down ("prepubertal dip"), only to be followed by the pubertal growth spurt. Sex hormones exert important growth effects during puberty, in addition to other factors such as growth hormone, thyroid hormones, nutrition, and insulin. Girls have their growth spurt early in puberty. Boys experience their growth spurt toward the end of puberty and achieve greater height velocities than girls. This, combined with the fact that boys grow for approximately 2 years more than girls, explains the 13 cm (5 inches) difference in final heights between the sexes.