LAUSR

Recent advances in embryo freezing technology together with growing concerns over multiple births have shifted the paradigm of appropriate IVF. This has led to the adoption of new performance indicators for ART clinics by national reporting schemes, such as those curated by the Society for Assisted Reproductive Technology (SART) and the Human Fertilization and Embryology Authority (HFEA). Using these organizations as case studies, we review several outcome measures from a statistical perspective. We describe several denominators that are used to calculate live birth rates. These include cumulative birth rates calculated from all fresh and frozen transfer procedures arising from a particular egg collection or cycle initiation, and live birth rates calculated per embryo transferred. Using data from both schemes, we argue that all cycles should be included in the denominator, regardless of whether or not egg collection and fertilization were successful. Excluding cancelled cycles reduces the impact of confounding due to patient characteristics but also removes policy and performance differences which we argue represent relevant sources of variation. It may be misleading to present prospective patients with essentially hypothetical measures of performance predicated on parity of ovarian stimulation and transfer policies. Although live birth per embryo has the advantage of encouraging single embryo transfer, we argue that it is prone to misinterpretation. This is because the likelihood of live birth is not proportional to the number of embryos transferred. We conclude that it is not possible to present a single measure that encompasses both effectiveness and safety. Instead, we propose that a set of clear, relevant outcome indicators is necessary to enable subfertile patients to make informed choices regarding whether and where to be treated.