This study aims to estimate short-term and long-term effects of time points to cease parenteral nutrition on very preterm infants, such as growth; to estimate the role of insulin-like growth factor 1 in the growth.

At present, it is unclear when to cease parenteral nutrition, the effects of cessation times on preterm infants' growth, and whether insulin-like growth factor 1 (IGF-1) has a mediation effect in the procedure that nutrients regulate the growth in preterm infants.

Therefore, a prospective cohort study was designed with the aims:

1. to estimate the association between the time to cease parenteral nutrition and the growth in very low birth weight;
2. to investigate the relationship between nutrient volume in parenteral nutrition and growth in very low birth weight;
3. to analyze the IGF-1 mediation effect between nutrient volume and growth regulations.

Inclusion Criteria:

1. Infants with a birth weight less than 1500 grams
2. Infants admitted within 72 hours after birth
3. Infants born from July 1, 2023, to June 30, 2024
4. Written informed consent from parents or guardians

Exclusion Criteria:

1. Infants with congenital abnormality
2. Infants surviving <7 days after birth

Very low birth weight infants(birth weight less than 1500 grams)