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.