Table 2 Inclusion and exclusion criteria

Gestational age between 28 and 36 weeks

Preterm infants require surgical intervention

Preterm infants without gastrointestinal diseases and eligible for breastfeeding

Premature infants need invasive ventilator therapy

All life signs were stable and remained stable for > 24 h

Premature infants with birth weight < 500 g

Parents are the main caregivers of premature infants, and those who can accompany them to the hospital on time

Those expected to be discharged within 1 week

Those whose guardians are able to communicate properly and who have signed an informed consent form

Mothers who have contraindications to breastfeeding or who have dropped out

Premature infants with congenital diseases, hereditary diseases, cranio-cerebral injuries or vital organ insufficiency