1. Department of Obstetrics and Gynaecology; Khon Kaen Hospital; Khon Kaen Thailand
2. Department of Obstetrics and Gynaecology, Faculty of Medicine; Khon Kaen University; Khon Kaen Thailand
3. Department of Epidemiology and Biostatistics, Faculty of Public Health; Khon Kaen University; Khon Kaen Thailand