1. Department of Obstetrics and Gynecology; Shanghai First People's Hospital Affiliated to Shanghai Jiao Tong University; Shanghai China
2. Department of Pathology; International Peace Maternity and Child Health Hospital Affiliated to Shanghai Jiao Tong University School of Medicine; Shanghai China
3. Department of Obstetrics and Gynecology; International Peace Maternity and Child Health Hospital Affiliated to Shanghai Jiao Tong University School of Medicine; Shanghai China