1. Shanghai Key Laboratory for Assisted Reproduction and Reproductive Genetics, Center for Reproductive Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong University , Shanghai 200135 , China
2. Department of Obstetrics and Gynaecology, Chinese University of Hong Kong , Hong Kong 999077 , China
3. Department of Development and Regeneration, Cluster Stem Cell Biology and Embryology, Research Unit of Stem Cell Research, University of Leuven (KU Leuven) , B-3000 Leuven , Belgium