Peripherel Perfusion Index to Predict Sepsis in Very Low Birth Weight Infants

This is a prospective observational study and does not include interventions. The exposure is peripheral perfusion index and the outcome is the incidence of late onset sepsis. From the day when the very low birth weight infant is admitted into hospital, PPI monitoring should be recorded once a day, and continuous monitoring would be recorded until 1 month after birth. Before collection, the infant will be confirmed to be in supine position with neutral temperature, and at the same time, the infant will be in a quiet state, without the contact and operation of medical personnel.