1. Department of Obstetrics and Gynecology, Hebei Medical University, Shijiazhuang 050017, China
2. Department of Obstetrics and Gynecology, Bethune International Peace Hospital, Shijiazhuang 050082, Hebei, China
3. Department of Reproductive Medicine Centre, Shijiazhuang Obstetrics and Gynecology Hospital, Shijiazhuang 050017, China