1. Florence Nightingale Faculty of Nursing, Midwifery & Palliative Care, King’s College London, 57 Waterloo Road, London SE1 8WA, UK
2. Warwick Clinical Trials Unit, University of Warwick, UK
3. School of Health Sciences, City, University of London, London, UK
4. Public Health and Epidemiology Group, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
5. Department of Midwifery, University College of Northern Denmark, Aalborg, Denmark
6. School of Health Sciences, University of Surrey, Guildford, UK