1. Faculty of Medicine, Chiang Mai University; Department of Obstetrics and Gynecology; 110 Intawaroros Road Muang Chiang Mai Thailand 50200
2. Khon Kaen University; Department of Obstetrics and Gynaecology, Faculty of Medicine; 123 Mitraparb Road Amphur Muang Khon Kaen Thailand 40002
3. Khon Kaen University; Department of Epidemiology and Biostatistics, Public Health Faculty; Mitraparp Road Mueng District Khon Kaen Khon Kaen Thailand 40002
4. Campbell Collaboration; New Delhi India