Ethical approval and consent to participate
This study was registered in the Chinese Clinical Trial Registry (Registration No: ChiCTR2100041910)(10/01/2021) and will be performed in accordance with the approved guidelines and regulations of the participating institutions. The research protocol was approved by the Ethics Committee of Women and Children’s Hospital affiliated with Xiamen University/Xiamen Maternal and Child Health Hospital (Batch number KY-2020–0086–01). Written informed consent was obtained from the parents or guardians of preterm infants included in the study.