1. Department of Obstetrics & Gynaecology, University of Cape Town, Observatory 7925, Cape Town, South Africa
2. Department of Obstetrics & Gynaecology, University of Zimbabwe, PO Box A178, Avondale, Harare, Zimbabwe
3. Department of Obstetrics & Gynaecology, University Hospital, S-751 85 Uppsala, Sweden
4. Department of Epidemiology and Public Health, Umeå, Sweden