1 Department of Prenatal Diagnosis, State Key Laboratory of Reproductive Medicine, Women's Hospital of Nanjing Medical University, Nanjing Maternity and Child Health Care Hospital, Nanjing, Jiangsu, PR China.
4 Department of Prenatal Diagnosis, State Key Laboratory of Reproductive Medicine, Women's Hospital of Nanjing Medical University, Nanjing Maternity and Child Health Care Hospital, Nanjing, Jiangsu, PR China. zhengfengxu@njmu.edu.cn.