1. Department of Obstetrics and Gynecology, Faculty of Medicine, Khon Kaen University, 123 Mitraparb Road, Amphur Muang, Khon Kaen 40002, Thailand
2. Department of Obstetrics and Gynecology, Rajavithi Hospital, College of Medicine, Rangsit University, Phayathai Road, Ratchathewi District, Bangkok 10400, Thailand
3. Department of Epidemiology and Biostatistics, Faculty of Public Health, Khon Kaen University, 123 Mitraparb Road, Amphur Muang, Khon Kaen 40002, Thailand
4. Department of Obstetrics and Gynecology, Faculty of Medicine, Chiang Mai University, 110 Inthawarorot St, Muang District, Muang Chiang Mai, Chiang Mai 50200, Thailand