1. Department of Health Science, Leicester Royal Infirmary, Leicester, United Kingdom
2. Medical Statistics Unit, London School of Hygiene and Tropical Medicine, London, United Kingdom
3. Health Services Research Unit, London School of Hygiene and Tropical Medicine, London, United Kingdom
4. Royal Victoria Infirmary, Newcastle Upon Tyne, United Kingdom
5. Liverpool Women's Hospital, Liverpool, United Kingdom
6. Rosie Hospital, Cambridge, United Kingdom
7. Royal Maternity Hospital, Belfast, Republic of Ireland
8. Institute of Child Health, London, United Kingdom