1. Department of Obstetrics and Gynaecology, Faculty of Clinical Sciences, College of Medicine/University College Hospital Ibadan, University of Ibadan, Ibadan, Nigeria
2. Institute of Advanced Medical Research and Training, College of Medicine, University of Ibadan, Ibadan, Nigeria
3. Department of Statistics, Faculty of Science, University of Ibadan, Ibadan, Nigeria
4. Department of Epidemiology and Medical Statistics, College of Medicine, Faculty of Public Health, University of Ibadan, Ibadan, Nigeria