Statement on Ethics

This study did not involve any departure from routine clinical practice or divisions/randomisation of patients into groups. It was retrospective in nature, using pre-existing audits of national database data from the British Society for Gynaecological Endoscopy (BSGE). Full anonymity of patients was ensured through lack of any patient-specific data used, only the number of operations were known for each endometriosis centre per year. For these reasons prior approval from a research ethics committee was not required. The audits were registered annually and performed by the BSGE, and are publicly available on their website. Approval was gained from the BSGE for the study.