The study has no external funding; all costs are covered by ESHRE. There are no competing interests.

STUDY QUESTION What are the reported data on cycles in ART, IUI and fertility preservation (FP) interventions in 2016 as compared to previous years, as well as the main trends over the years? SUMMARY ANSWER The 20th ESHRE report on ART and IUI shows a progressive increase in reported treatment cycle numbers in Europe, with a decrease in the number of transfers with more than one embryo causing a reduction of multiple delivery rates (DR), as well as higher pregnancy rates and DR after frozen embryo replacement (FER) compared to fresh IVF and ICSI cycles, while the outcomes for IUI cycles remained stable. WHAT IS KNOWN ALREADY Since 1997, ART aggregated data generated by national registries, clinics or professional societies have been collected, analysed by the European IVF-monitoring Consortium (EIM) and reported in 19 manuscripts published in Human Reproduction and Human Reproduction Open. STUDY DESIGN, SIZE, DURATION Yearly collection of European medically assisted reproduction (MAR) data by EIM for ESHRE. The data on treatments performed between 1 January and 31 December 2016 in 40 European countries were provided by either National Registries or registries based on personal initiatives of medical associations and scientific organizations. PARTICIPANTS/MATERIALS, SETTING, METHODS In all, 1347 clinics offering ART services in 40 countries reported a total of 918 159 treatment cycles, involving 156 002 with IVF, 407 222 with ICSI, 248 407 with FER, 27 069 with preimplantation genetic testing, 73 927 with egg donation (ED), 654 with IVM of oocytes and 4878 cycles with frozen oocyte replacement (FOR). European data on IUI using husband/partner’s semen (IUI-H) and donor semen (IUI-D) were reported from 1197 institutions offering IUI in 29 and 24 countries, respectively. A total of 162 948 treatments with IUI-H and 50 467 treatments with IUI-D were included. A total of 13 689 FP interventions from 11 countries including oocyte, ovarian tissue, semen and testicular tissue banking in pre-and postpubertal patients were reported. MAIN RESULTS AND THE ROLE OF CHANCE In 20 countries (18 in 2015) with a total population of approximately 325 million inhabitants, in which all ART clinics reported to the registry, a total of 461 401 treatment cycles were performed, corresponding to a mean of 1410 cycles per million inhabitants (range 82–3088 per million inhabitants). In the 40 reporting countries, after IVF the clinical pregnancy rates (PR) per aspiration and per transfer in 2016 were similar to those observed in 2015 (28.0% and 34.8% vs 28.5% and 34.6%, respectively). After ICSI, the corresponding rates were also similar to those achieved in 2015 (25% and 33.2% vs 26.2% and 33.2%). After FER with own embryos, the PR per thawing is still on the rise, from 29.2% in 2015 to 30.9% in 2016. After ED, the PR per fresh embryo transfer was 49.4% (49.6% in 2015) and per FOR 43.6% (43.4% in 2015). In IVF and ICSI together, the trend towards the transfer of fewer embryos continues with the transfer of 1, 2, 3 and ≥4 embryos in 41.5%, 51.9%, 6.2% and 0.4% of all treatments, respectively (corresponding to 37.7%, 53.9%, 7.9% and 0.5% in 2015). This resulted in a proportion of singleton, twin and triplet DRs of 84.8%, 14.9% and 0.3%, respectively (compared to 83.1%, 16.5% and 0.4%, respectively in 2015). Treatments with FER in 2016 resulted in twin and triplet DR of 11.9% and 0.2%, respectively (vs 12.3% and 0.3% in 2015). After IUI, the DRs remained similar at 8.9% after IUI-H (7.8% in 2015) and at 12.4% after IUI-D (12.0% in 2015). Twin and triplet DRs after IUI-H were 8.8% and 0.3%, respectively (in 2015: 8.9% and 0.5%) and 7.7% and 0.4% after IUI-D (in 2015: 7.3% and 0.6%). The majority of FP interventions included the cryopreservation of ejaculated sperm (n = 7877 from 11 countries) and of oocytes (n = 4907 from eight countries). LIMITATIONS, REASONS FOR CAUTION As the methods of data collection and levels of completeness of reported data vary among European countries, the results should be interpreted with caution. A number of countries failed to provide adequate data about the number of initiated cycles and deliveries. WIDER IMPLICATIONS OF THE FINDINGS The 20th ESHRE report on ART and IUI shows a continuous increase of reported treatment numbers and MAR-derived livebirths in Europe. Being already the largest data collection on MAR in Europe, continuous efforts to stimulate data collection and reporting strive for future quality control of the data, transparency and vigilance in the field of reproductive medicine. STUDY FUNDING/COMPETING INTEREST(S) The study has no external funding and all costs were covered by ESHRE. There are no competing interests.

STUDY QUESTION How has the performance of the European regional register of the European IVF-monitoring Consortium (EIM)/European Society of Human Reproduction and Embryology (ESHRE) evolved from 1997 to 2016, as compared to the register of the Centres for Disease Control and Prevention (CDC) of the USA and the Australia and New Zealand Assisted Reproduction Database (ANZARD)? SUMMARY ANSWER It was found that coherent and analogous changes are recorded in the three regional registers over time, with a different intensity and pace, that new technologies are taken up with considerable delay and that incidental complications and adverse events are only recorded sporadically. WHAT IS KNOWN ALREADY European data on ART have been collected since 1997 by EIM. Data collection on ART in Europe is particularly difficult due to its fragmented political and legal landscape. In 1997, approximately 78.1% of all known institutions offering ART services in 23 European countries submitted data and in 2016 this number rose to 91.8% in 40 countries. STUDY DESIGN, SIZE, DURATION We compared the changes in European ART data as published in the EIM reports (2001–2020) with those of the USA, as published by CDC, and with those of Australia and New Zealand, as published by ANZARD. PARTICIPANTS/MATERIALS, SETTING, METHODS We performed a retrospective analysis of the published EIM data sets spanning the 20 years observance period from 1997 to 2016, together with the published data sets of the USA as well as of Australia and New Zealand. By comparing the data sets in these three large registers, we analysed differences in the completeness of the recordings together with differences in the time intervals on the occurrence of important trends in each of them. Effects of suspected over- and under-reporting were also compared between the three registers. X2 log-rank analysis was used to assess differences in the data sets. MAIN RESULTS AND THE ROLE OF CHANCE During the period 1997–2016, the numbers of recorded ART treatments increased considerably (5.3-fold in Europe, 4.6-fold in the USA, 3.0-fold in Australia and New Zealand), while the number of registered treatment modalities rose from 3 to 7 in Europe, from 4 to 10 in the USA and from 5 to 8 in Australia and New Zealand, as published by EIM, CDC and ANZARD, respectively. The uptake of new treatment modalities over time has been very different in the three registers. There is a considerable degree of underreporting of the number of initiated treatment cycles in Europe. The relationship between IVF and ICSI and between fresh and thawing cycles evolved similarly in the three geographical areas. The freeze-all strategy is increasingly being adopted by all areas, but in Europe with much delay. Fewer cycles with the transfer of two or more embryos were reported in all three geographical areas. The delivery rate per embryo transfer in thawing cycles bypassed that in fresh cycles in the USA in 2012, in Australia and New Zealand in 2013, but not yet in Europe. As a result of these changing approaches, fewer multiple deliveries have been reported. Since 2012, the most documented adverse event of ART in all three registers has been premature birth (<37 weeks). Some adverse events, such as maternal death, ovarian hyperstimulation syndrome, haemorrhage and infections, were only recorded by EIM and ANZARD. LIMITATIONS, REASONS FOR CAUTION The methods of data collection and reporting were very different among European countries, but also among the three registers. The better the legal background on ART surveillance, the more complete are the data sets. Until the legal obligation to report is installed in all European countries together with an appropriate quality control of the submitted data the reported numbers and incidences should be interpreted with caution. WIDER IMPLICATIONS OF THE FINDINGS The growing number of reported treatments in ART, the higher variability in treatment modalities and the rising contribution to the birth rates over the last 20 years point towards the increasing impact of ART. High levels of completeness in data reporting have been reached, but inconsistencies and inaccuracies still remain and need to be identified and quantified. The current trend towards a higher diversity in treatment modalities and the rising impact of cryostorage, resulting in improved safety during and after ART treatment, require changes in the organization of surveillance in ART. The present comparison must stimulate all stakeholders in ART to optimize surveillance and data quality assurance in ART. STUDY FUNDING/COMPETING INTEREST(S) This study has no external funding and all costs are covered by ESHRE. There are no competing interests. TRIAL REGISTRATION NUMBER N/A.

Healthy young women showed psychological and physical symptoms during the menstrual cycle which changed in association with alterations in low-grade inflammation and which were independent of body weight or plasma levels of gonadal steroids.