1. Department of Community Medicine, Occupational Health Unit, University College Hospital, Ibadan, Nigeria;
2. Department of Obstetrics and Gynaecology, University College Hospital, Ibadan, Nigeria;
3. Department of Community Medicine, Family and Reproductive Health Unit, University College Hospital, Ibadan, Nigeria;
4. Occupational Medicine Program, Division of Preventive Medicine, University of Alberta, Edmonton, Canada;
5. Department of Environmental and Occupational Health, School of Public Health, Drexel University, Philadelphia, PA, USA