1. Policy Research Unit in Maternal Health and Care; National Perinatal Epidemiology Unit (NPEU); Nuffield Department of Population Health; University of Oxford; Oxford UK
2. Birmingham Clinical Trials Unit; University of Birmingham; Birmingham UK
3. Nuffield Department of Obstetrics and Gynaecology; John Radcliffe Hospital; University of Oxford; Oxford UK
4. Department of Obstetrics and Gynaecology; Sunderland Royal Hospital; Sunderland UK
5. Department of Anaesthetics; Northwick Park Hospital; London UK
6. Neonatal Unit; Royal Infirmary of Edinburgh; Edinburgh UK
7. Bradford Teaching Hospitals Foundation NHS Trust; Bradford UK