*Department of Pain, Women’s Hospital of Nanjing Medical University, Nanjing Maternity and Child Health Care Hospital, Nanjing City, Jiangsu Province

†Department of Pain, Beijing Shijitan Hospital, Capital Medical University

‡Department of Pain, Beijing Xuanwu Hospital, Capital Medical University, Beijing, China

The authors declare no conflict of interest.

Reprints: Liangliang He, MD, Department of Pain, Beijing Xuanwu Hospital, Capital Medical University, No. 45 Changchun Street, Xicheng District, Beijing, China, 100053 (e-mail: [email protected]).