1. Department of Obstetrics and Gynaecology; Faculty of Medicine, Khon Kaen University; 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
4. OB/GYN and Reproductive Sciences; University of California, San Diego; La Jolla CA USA