1. Khon Kaen Hospital; Department of Obstetrics and Gynaecology; Srichan Road Maung Khon Kaen Thailand 40000
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 Biostatistics and Demography, Faculty of Public Health; Khon Kaen Thailand 40002
4. Academic Medical Centre, University of Amsterdam; Obstetrics and Gynaecology; Meibergdreef 9 PO Box 22700 Amsterdam Netherlands 1105 AZ