1. OMNI Research Group, Department of Obstetrics & Gynecology, University of Ottawa, Faculty of Medicine, Ottawa, Canada.
2. Department of Nursing, Huaihua Medical College, Huaihua, China.
3. Ottawa Hospital Research Institute, Clinical Epidemiology Program, Ottawa, Canada.
4. The Third Xiang Ya Hospital of Central South University, Changsha, China.
5. Xiangya Hospital of Central South University, Changsha, China.
6. University of South China School of Nursing, Hunan, P.R. China.
7. Department of Epidemiology and Community Medicine, University of Ottawa Faculty of Medicine, Ottawa, Canada.