1. Clínica Euskalduna, Bilbao, Spain;
2. AP-OSI Research Unit, Alto Deba Hospital, Mondragón, Gipuzkoa, Spain;
3. Division for Family Planning, University Hospital Zürich, Zürich, Switzerland;
4. Department of Gynaecology and Obstetrics, Burgos University Hospital, Burgos, Spain;
5. Faculty of Health and Social Sciences, Bournemouth University, Bournemouth, UK;
6. Health Services Research on Chronic Patients Network (REDISSEC), Bilbao, Spain;
7. Clinical Management Unit, Alto Deba Hospital, Mondragón, Gipuzkoa, Spain