1. Khon Kaen University; Department of Obstetrics and Gynaecology, Faculty of Medicine; 123 Mitraparb Road Amphur Muang Khon Kaen Thailand 40002
2. Khon Kaen University; Department of Demography and Biostatistics; Faculty of Public Health Khon Kaen Thailand 40002
3. Oregon Health and Science University; Department of Obstetrics and Gynecology; 3181 S.W. Sam Jackson Park Road Portland Oregon USA 97239