Smaller-than-gestational-age children are newborns whose birth weight and/or length are below the 10th percentile of the mean for the same gestational age and sex or 2 standard deviations below the mean. The incidence of SGA in the population is 3%-10%, and the incidence in China is about 7.5%, of which 10%-15% of children with SGA have no postnatal catch-up growth. About half of these children with growth disorders will have an adult height that is 2 standard deviations below the normal average height, and eventual adult short stature. There are many causes of SGA, including maternal factors, fetal self factors, placental and umbilical cord factors, and endocrine factors. Studies have proven that serum concentrations of insulin, IGF-1 and IGFBP-3 are closely associated with growth catch-up induced with growth hormone before puberty. Numerous studies have confirmed that GH application during childhood and prepubertal period can lead to normal height in children with dwarf SGA and can lead to a final height of expected height.