1. Nuffield Department of Primary Care Health Sciences; University of Oxford; Oxford UK
2. Women's Health Research Unit; Barts and the London School of Medicine and Dentistry; London UK
3. Royal Free London NHS Trust; London UK
4. Neonatal Medicine; Faculty of Medicine; Imperial College London; London UK
5. Clinical Biostatistics Unit; Ramon y Cajal Institute of Research and Centro de Investigación Biomédica en Red Epidemiology and Public Health; Madrid Spain
6. Cochrane Gynaecology and Fertility Group; University of Auckland; Auckland New Zealand
7. MRC North West Hub for Trials Methodology Research; Institute of Translational Medicine; University of Liverpool; Liverpool UK