Participants
This is a prospective diagnostic accuracy study following STARD (Standards for the Reporting of Diagnostic Accuracy Studies) guidelines19.The study was conducted at a top-ranking obstetrics and gynaecology hospital in China between 2019 to 2020. All inborn infants were given birth in our hospital and were transferred to a monitoring room for 6-hour monitoring before going back to their mothers(healthy infants) or admission to NICU( infants with respiratory issues or other diseases). (Fig1.A) Infants who have respiratory symptoms, including anhelation, retractions, or transcutaneous oxygen saturation(TcSO2) constantly below 95% were considered eligible for the study. Then they were confirmed to be healthy or in need of respiratory support through a 3-day follow up. Exclusion criteria are following: (1) chromosomal abnormalities or complex congenital malformations; (2) congenital lung diseases; (3) were transferred to other hospitals so that can not be followed up; (4) without qualified LUS images or complete data;