1. Department of Neonatology, The Second Hospital, Cheeloo College of Medicine, Shandong University, Jinan, Shandong, 250033, China
2. Huantai County Maternal and Child Health Care Hospital of Zibo City, Zibo, Shandong, 256400, China
3. Zaozhuang Maternal and Children’s Hospital, Zaozhuang, Shandong, 277100, China
4. Zibo Maternity and Child Health Care Hospital, Zibo, Shandong, 256400, China