STUDY QUESTION What were the rates of utilization, effectiveness, and safety for assisted reproductive technology (ART) throughout the world in 2017 and 2018, and what trends were observed?SUMMARY ANSWER The total reported number of ART fresh and frozen cycles conducted in 83 participating countries was 2 913 498 in 2017 and 3 303 505 in 2018, with 5-year trends including an increasing proportion of cycles utilizing frozen embryo transfer (FET) and an increasing number of cycles utilizing pre-implantation genetic testing (PGT).WHAT IS KNOWN ALREADY Prior reports from the International Committee Monitoring ART (ICMART) have reported on the utilization, effectiveness, and safety of ART from participating countries, with an increase in the number of cycles and number of participating countries over time. These reports have described regional differences in the utilization of ART overall, as well as differences in the utilization of specific practices such as ICSI, PGT and single embryo transfer. Past reports demonstrated that rates of delivery per cycle have increased and rates of multiple gestations have decreased over time.STUDY DESIGN, SIZE, DURATION This retrospective, cross-sectional survey describes ART procedures performed globally in 2017 and 2018. Data were submitted to ICMART by participating countries from national or regional registries.PARTICIPANTS/MATERIALS, SETTING, METHODS There were 83 countries which provided data for cycles performed in 2017 or 2018, with the majority of countries providing data for both years. Aggregate data are reported for each participating country and analysed using methods developed by ICMART to calculate measures of utilization, effectiveness, and safety.MAIN RESULTS AND THE ROLE OF CHANCE A total of 2 913 498 cycles and 671 012 babies born were reported for treatment performed in 2017, increasing to 3 303 505 cycles and 728 383 babies born for treatment performed in 2018. After imputing data for non-reporting centres in reporting countries, the estimated number of cycles performed in 2017 was 3 107 188 resulting in an estimated 814 588 babies. For 2018, the estimated number of cycles was 3 568 635 resulting in an estimated 870 814 babies. Utilization of ICSI for autologous fresh non-PGT cycles declined slightly compared with 2014 (54.6% in 2017 and 57.3% in 2018 compared with 64.8% in 2014). The percentage of transfers which were of frozen embryos was 55.7 % in 2017 and 57.9% in 2018, up from 38.9% in 2014. Among all countries, including those which reported no 'freeze all' cycles, the percentage of 'freeze all' cycles was 30.5% in 2017 and 32.7% in 2018, up from 13.1% in 2014. In countries reporting at least one retrieval cycle in which all embryos were frozen, the percentage of retrievals with no fresh embryo transfer increased (36.2% in 2017 and 36.8% in 2018, up from 20.1% in 2014). The number of PGT cycles in 2018 (172 247) was nearly 5-fold higher than the number reported in 2014 (36 512) with wide regional variation in utilization of PGT observed. In 2017, the delivery rate for autologous oocytes was 23.5% per oocyte retrieval, with a cumulative delivery rate of 36.4% per retrieval (excluding cycles which utilized PGT). The delivery rates per embryo transfer were 31.8% per autologous fresh transfer, 32.5% per autologous frozen transfer, and 47.3% per transfer after PGT. The delivery rate for transfers utilizing donor oocytes was 33.1% (combined fresh transfer and frozen transfers). In 2018, the delivery rate for autologous oocytes was 23.