This study was used to determine the relationship between vitamin D receptor gene polymorphism and children's physical and intellectual development, further adjust the doses of vitamin D supplementation after birth, and provide individualized vitamin D and calcium supplements.

High risk children aged 0-3 years old who visited the pediatrics clinic and ward of the first affiliated hospital of Xi'an Jiaotong university and other cooperative hospitals from 2018 to 2020 were randomly selected. Personal information of the children and parents who were enrollment was collected by questionnaire survey and a follow-up file was established. 500 to 1,000 people are planned to participate in the study, were randomly divided into research group and the control group. Then collect the sample(saliva) of children to examine Vitamin D Receptor(VDR) genotype, according to results, divide the research group into high, medium and low risk, given individual vitamin D and calcium supplement. Monitor the children's weight, body length, head circumference, the Neonatal Behavioral Assessment Scale(NBAS), bailey rating scale respectively, up to 3 years old. All sample analyses were performed by the Gene Medical Laboratory. Laboratory personnel were blinded to mother and infant outcomes.

Inclusion Criteria:

• infant age from 0 to 3 years old
• enjoy good health, there is no history of specific diseases

Exclusion Criteria:

• this time or always exists serious lung infection, or with nervous system disease, kidney disease, malignant tumor, etc
• has bone metabolic diseases or other genetic metabolic disease
• taking affect bone metabolism of drugs for a long time