In order to create a better environment for growth and development for very low birth weight infants(VLBWIs), investigators introduce quiet time, which is an intervention method that reduces environmental noise in the ward and centralizes medical and nursing operations. By analyzing the weight gain of VLBWIs in the intervention group and the control group during hospitalization, the effect of setting a quiet time in the NICU on improving the growth and development of VLBWIs is evaluated.

Inclusion Criteria:

• Birth weight <1500g;
• Admit within 24 hours of birth;
• The guardian signs the informed consent.

Exclusion Criteria:

• Newborn with severe congenital malformations or various chromosomal diseases, genetic metabolic diseases, severe neurological diseases;
• Newborn who do not achieve discharge or death at the end of the study period.