1. Department of Pathology and Department of Obstetrics and Gynecology, West China Second University Hospital, Sichuan University , Chengdu , China
2. Key Laboratory of Birth Defects and Related Diseases of Women and Children, Sichuan University, Ministry of Education , Chengdu , China
3. Department of Pathology, University of Pittsburgh Medical Center , Pittsburgh, PA , US
4. Department of Obstetrics and Gynecology, West China Second University Hospital, Sichuan University , Chengdu , China