1. Department of Obstetrics and Gynecology, Tangshan Worker Hospital, Hebei Medical University, Tangshan, Hebei 063000, P.R. China
2. Department of Rheumatology and Immunology, Tianjin General Hospital, Tianjin Medical University, Tianjin 300052, P.R. China
3. Department of Rheumatology and Immunology, Tangshan Worker Hospital, Hebei Medical University, Tangshan, Hebei 063000, P.R. China