1. Department of Obstetrics and Gynaecology, University College Hospital , Ibadan 200212 , Nigeria
2. Department of Obstetrics and Gynecology , College of Medicine, , Ibadan 200005 , Nigeria
3. University of Ibadan , College of Medicine, , Ibadan 200005 , Nigeria
4. Department of Obstetrics and Gynecology, Lagos State University College of Medicine/Lagos State University Teaching Hospital , Ikeja 100254 , Nigeria
5. Department of Statistics , Faculty of Science, , Ibadan 200005 , Nigeria
6. University of Ibadan , Faculty of Science, , Ibadan 200005 , Nigeria
7. Institute of Advanced Medical Research and Training , College of Medicine, , Ibadan 200212 , Nigeria
8. University of Ibadan , College of Medicine, , Ibadan 200212 , Nigeria