Inclusion Criteria:  Live born newborns with gestational age ≤ 36 + 6 weeks Transfer to the neonatal ward of Shanghai Children's medical center within 24 hours after birth Those who have lived in Shanghai for more than 1 year and plan to live in Shanghai for a long time. Parents voluntarily participated in the study and signed informed consent  Exclusion Criteria:  Premature infants: termination of treatment due to family factors (non-disease reasons) and hospitalization time ≤ 2 weeks Major congenital malformations Parents refuse to participate in the study