More than 20 years ago, the survey of activities in medically assisted reproduction (MAR) was initiated in Europe and resulted in cross-sectional annual reports, as issued by the European IVF Monitoring (EIM) consortium of ESHRE. Over time, these reports mirror the continuous development of the technologies and contribute to increased transparency and surveillance of reproductive care. Meanwhile, progressive changes of existing treatment modalities and the introduction of new technologies resulted in the need of a cumulative approach in the assessment of treatment outcomes, which warrants a prospective cycle-by-cycle data registry on MAR activities, including fertility preservation. This change in the paradigm of data collection in Europe towards the construction of cumulative outcome results is expected to generate additional insights into cross-institutional but also cross-border movements of patients and reproductive material. This is essential to improve vigilance and surveillance. The European monitoring of Medically Assisted Reproduction (EuMAR) project, co-funded by the European Union, will establish a registry for the transnational collection of prospective cycle-by-cycle MAR and fertility preservation data on the basis of an individual reproductive care code (IRCC). The rationale for the project and the objectives are presented here.
Pre-conception counselling and management of expectations about chance of success of IVF/ICSI treatments is an integral part of fertility care. Registry data are usually used to inform patients about expected success rates of IVF/ICSI treatment, as these data should best represent real-world populations and clinical practice. In registries, the success rate of IVF/ICSI treatments is conventionally reported per treatment cycle or per embryo transfer and estimated from data for which several treatment attempts per subject have been pooled (e.g. repetitive IVF/ICSI attempts or repetitive attempts of cryotransfer). This, however, may underestimate the true mean chance of success per treatment attempt, because treatment attempts of women with a poor prognosis will usually be over-represented in a pool of treatment cycle data compared to treatment events of women with a good prognosis. Of note, this phenomenon is also a source of potential bias when comparing outcomes between fresh transfers and cryotransfers, since women can undergo a maximum of only one fresh transfer after each IVF/ICSI treatment, but potentially several cryotransfers. Herein, we use a trial dataset from 619 women, who underwent one cycle of ovarian stimulation and ICSI, a Day 5 fresh transfer and/or subsequent cryotransfers (follow-up of all cryotransfers up to 1 year after the start of stimulation), to exemplify the underestimation of the live birth rate, when not accounting for repeated transfers in the same woman. Using mixed-effect logistic regression modelling, we show that the mean live birth rate per transfer per woman in cryocycles is underestimated by the factor 0.69 (e.g. live birth rate per cryotransfer of 36% after adjustment versus 25% unadjusted). We conclude that the average chance of success of treatment cycles of women of a given age, treated in a given centre, etc., when conventionally calculated per cycle or per embryo transfer from a pool of treatment events, do not apply to an individual woman. We suggest that patients are, especially at the outset of treatment, systematically confronted with mean estimates of success per attempt that are too low. Live birth rates per transfer from datasets encompassing multiple transfers from single individuals could be more accurately reported using statistical models accounting for the correlation between cycle outcomes within women.
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