1. Central Research Laboratory, The Second Hospital, Cheeloo College of Medicine, Shandong University, Jinan 250033, P.R. China
2. Department of Biostatistics, School of Public Health, Cheeloo Collage of Medicine, Shandong University, Jinan 250012, P.R. China
3. Center for Reproductive Medicine, Shandong Provincial Hospital Affiliated with Shandong University, Jinan 250001, P.R. China
4. Department of Critical Care Medicine, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Science, Beijing 100730, P.R. China
5. Department of Gynecology and Obstetrics, Liaocheng People’s Hospital, Liaocheng 252000, P.R. China