Journal of the European Society for Gynaecological Endoscopy


An International Terminology for Endometriosis, 2021

International Working Group of AAGL, ESGE, ESHRE and WES, C. Tomassetti 1, N.P. Johnson 2, J. Petrozza 3, M.S. Abrao 4,5, J.I. Einarsson 6, A.W. Horne 7, T.T.M. Lee 8, S. Missmer 9,10,11, N. Vermeulen 12, K.T. Zondervan 13,14, G. Grimbizis 15, R.L. De Wilde 16

1 University Hospital Leuven, Department of Obstetrics and Gynaecology, Leuven University Fertility Centre, Leuven, Belgium
2 Robinson Research Institute, University of Adelaide, Adelaide, South Australia
3 Massachusetts General Hospital Fertility Center, Department of Obstetrics and Gynecology, Boston, MA, USA
4 Disciplina de Ginecologia, Departamento de Obstetricia e Ginecologia, Faculdade de Medicina FMUSP, Universidade de Sao Paulo, São Paulo, SP, Brazil
5 Gynecologic Division, BP - A Beneficencia Portuguesa de Sao Paulo, São Paulo, SP, Brazil
6 Brigham and Women’s Hospital, Department of Obstetrics and Gynecology, Division of Minimally Invasive Gynecologic Surgery, Boston, MA, USA
7 University of Edinburgh, MRC Centre for Reproductive Health, QMRI, 49 Little France Crescent, Edinburgh, UK EH16 4TJ
8 Magee Womens Hospital of UPMC, Department of Obstetrics, Gynecology and Reproductive Sciences, Pittsburgh, PA, USA
9 Michigan State University College of Human Medicine, Department of Obstetrics, Gynecology and Reproductive Biology, East Lansing, MI, USA
10 Harvard University T H Chan School of Public Health, Department of Epidemiology, Boston, MA, USA
11 World Endometriosis Research Foundation, WERF, London, UK;
12 ESHRE, Central office, Meerstraat 60, Grimbergen, BE 1852, Belgium
13 University of Oxford, Oxford Endometriosis CaRe Centre, Nuffield Department of Women’s & Reproductive Health, Oxford, Oxfordshire, UK
14 University of Oxford, Wellcome Centre for Human Genetics, Oxford, Oxfordshire, UK
15 Medical School, Aristotle University of Thessaloniki, 1st Dept Obstet Gynecol, Tsimiski 51 Street, Thessaloniki, Greece 54623
16 Carl von Ossietzky Universitat Oldenburg, University Hospital for Gynecology, Oldenburg, Germany.


Endometriosis, glossary, terminology, endometrioma, excision, ablation, coagulation

Published online: Oct 22 2021


Background: Different classification systems have been developed for endometriosis, using different definitions for the disease, the different subtypes, symptoms and treatments. In addition, an International Glossary on Infertility and Fertility Care was published in 2017 by the International Committee for Monitoring Assisted Reproductive Technologies (ICMART) in collaboration with other organisations. An international working group convened over the development of a classification or descriptive system for endometriosis. As a basis for such system, a terminology for endometriosis was considered a condition sine qua non.

Objectives: The aim of the current paper is to develop a set of terms and definitions on endometriosis that would be the basis for standardisation in disease description, classification and research.

Materials and Methods: The working group listed a number of terms relevant to be included in the terminology, documented currently used and published definitions, and discussed and adapted them until consensus was reached within the working group. Following stakeholder review, further terms were added, and definitions further clarified. Although definitions were collected through published literature, the final set of terms and definitions is to be considered consensus-based. After finalisation of the first draft, the members of the international societies and other stakeholders were consulted for feedback and comments, which led to further adaptations.

Results: A list of 49 terms and definitions in the field of endometriosis is presented, including a definition for endometriosis and its subtypes, different locations, interventions, symptoms and outcomes. Endometriosis is defined as a disease characterised by the presence of endometrium-like epithelium and/or stroma outside the endometrium and myometrium, usually with an associated inflammatory process.

Conclusions: The current paper outlines a list of 49 terms and definitions in the field of endometriosis. The application of the defined terms aims to facilitate harmonisation in endometriosis research and clinical practice. Future research may require further refinement of the presented definitions.

What is new? A consensus based international terminology for endometriosis for clinical and research use.