1. Department of Obstetrics and Gynecology, Hunan Provincial Maternal and Child Health Care Hospital (Reproductive Medicine Institute of Hunan Province) , Changsha 410008, Hunan Province , P.R. China
2. National Health Commission Key Laboratory of Birth Defects Research, Prevention and Treatment, Hunan Provincial Maternal and Child Health Care Hospital , Changsha 410008, Hunan Province , P.R. China
3. Department of Obstetrics and Gynecology, Qingdao Municipal Hospital , Qingdao 266000, Shandong Province , P.R. China