Cognitive impairment is independently related to low birth weight, low birth length and small head circumference. SGA children who have not experienced height and / or head circumference catch-up have the worst cognitive function. The serum IGF-1 level of short SGA children is significantly lower than that of catch-up SGA children. This may be due to the defect of GH-IGF-1 axis, resulting in some hGH / IGF-1 deficiency. GH treatment can induce catch-up growth of head circumference, especially for those with small birth head circumference, growth hormone can help to improve IQ, behavior and self cognition of children with SGA. Two years after birth is the most critical period for children's physical, neurological, cognitive and emotional development. This study evaluated the effect of growth hormone treatment on the improvement of cognitive function and growth and development of symmetrical SGA children who did not show catch-up growth from 6 months to 2 years old. This is an innovative study. The minimum age of previous similar studies is 19 months. The starting age of this study is 6 months, and the results are to improve the cognitive development of SGA infants. This is the first of its kind. Although the safety of growth hormone in SGA infants younger than 2 years old has not been reported, it is based on a number of studies on the application of growth hormone in infants, such as PWS and GHD, It can be expected that there will be no short-term and long-term adverse reactions. The study was conducted in 17 hospitals led by Tongji Hospital Affiliated to Tongji Medical College of Huazhong University of science and technology