1. Hebei University Health Science Center, Baoding, China
2. Institute for Reproductive Medicine of Hebei University, Baoding, China
3. Center for Reproductive Medicine of Affiliated Hospital of Hebei University, Baoding, China
4. Hebei Research Institute for Family Planning, Shijiazhuang, China
5. The Center for Reproductive Medicine of Peking University Third Hospital, Beijing, China
6. State Key Laboratory of Stem Cell and Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
7. University of Chinese Academy of Sciences, Beijing, China