1. Reproductive Medicine Center and Prenatal Diagnosis Center, Shijiazhuang Obstetrics and Gynecology Hospital, Shijiazhuang, Hebei 050011, P.R. China
2. Department of Science and Technology, Hebei University of Chinese Medicine, Shijiazhuang, Hebei 050200, P.R. China
3. Department of Gynecology and Obstetrics, Shijiazhuang Obstetrics and Gynecology Hospital, Shijiazhuang, Hebei 050011, P.R. China