1. National Guideline Alliance, The Royal College of Obstetricians and Gynaecologists, London, SE1 1SZ, UK
2. Department of Gynaecology, Royal Cornwall Hospitals NHS Trust, Truro, TR1 3LQ, UK
3. British Pregnancy Advisory Service, Stratford-upon-Avon, CV37 9BF, UK
4. Sexual and Reproductive Health Services, NHS Lothian, Edinburgh, EH3 9ES, Scotland