Footnotes

• JNH and ET contributed equally.

• Contributors The authors were involved in the study activities listed. JNH: methodology, data analysis, interpretation of results, writing manuscript and editing. ET: data collection and recruitment of participants, methodology, data analysis, interpretation of results and writing manuscript. KG-D: conceptualisation, methodology, interpretation of results, review and editing. ML: conceptualisation, methodology, interpretation of results, review and editing. MM: recruitment process, methodology, interpretation of results, review and editing. IS-P: conceptualisation, methodology, interpretation of results, review and editing. TT: conceptualisation, data collection and recruitment, methodology, interpretation of results, review and editing. MER: conceptualisation, data collection and recruitment, methodology, funding acquisition, project administration, interpretation of results, writing manuscript and editing.

• Funding The Family Planning Fund in Uppsala, Faculty of Medicine, Lund University.

• Competing interests KG-D has received consulting fees and/or payment or honoraria from Bayer, MSD, Gedeon Richter, Mithra, Exeltis, MedinCell, Cirqle, Natural Cycles, Exelgyn, Campus Pharma and HRA-Pharma. KG-D has been involved in data safety monitoring boards or advisory boards of Gedeon Richter and Bayer. KG-D has had reading roles (unpaid) for FIGO, WHO HRP/SRH, the European Society for Contraception and Reproductive Health, FIAPAC and FSRH/RCOG (UK). IS-P has served occasionally on advisory boards or acted as an invited speaker at scientific meetings for Asarina Pharma, Bayer Health Care, Gedeon Richter, Peptonics, Shire/Takeda and Sandoz. None of the other authors report any conflicts of interest.

• Provenance and peer review Not commissioned; externally peer reviewed.