1. Faculty of Medicine Vajira Hospital, Navamindradhiraj University; Department of Obstetrics and Gynaecology; 681 Samsen Road Dusit District Bangkok Thailand 10300
2. Research Facilitation Divison, Faculty of Medicine Vajira Hospital; Navamindradhirij University Khon Kaen Thailand 40002
3. Khon Kaen University; Department of Biostatistics and Demography, Faculty of Public Health; 123 Mitraparb Road Amphur Muang Khon Kaen Thailand 40002
4. Khon Kaen University; Department of Obstetrics and Gynaecology, Faculty of Medicine; 123 Mitraparb Road Amphur Muang Khon Kaen Thailand 40002
5. Newcastle University; Institute of Health & Society; Medical School New Build Richardson Road Newcastle upon Tyne UK NE2 4AX