1. Department of obstetrics and gynecology, Qinhuangdao Maternal and Child Health Hospital, Qinhuangdao, Hebei, China
2. Department of Neurology, Shaanxi Provincial People’s Hospital, Xi’an, Shaanxi, China
3. Department of Gynecology, Shaanxi Provincial People’s Hospital, Xi’an, Shaanxi, 710068, China.