Inclusion Criteria:  Single birth, clinical diagnosis of SGA; rhGH treatment beginned before puberty (Tanner stage I), regardless of gender; Before starting rhGH treatment, height was lower than -2 SDS compared with normal children of the same age and sex; All the subjects and their guardians signed the informed consent and the informed consent for genetic testing.  Exclusion Criteria:  No efficacy and safety data were recorded after treatment with rhGH; A history of blood transfusion within 3 months before the collection of the genetic blood samples, or a history of bone marrow transplantation between rhGH treatment and the enrollment in this study; Other conditions that the investigator considered unsuitable for inclusion in this study.