Approaches to frozen embryo transfer: a Canadian Fertility and Andrology Society (CFAS) guideline

<h2>Abstract</h2> This guideline provides evidence-based recommendations drawn exclusively from recent randomized control trials, for the clinical management of frozen embryo transfer (FET). In Canada, the incidence of freeze all cycles has increased from 24% to 78% over the last decade. While a freeze all strategy can be a pivotal tool for the prevention of ovarian hyper stimulation syndrome (OHSS), the available data do not support its routine use for improving live birth rates (LBR), reducing pregnancy loss (PL), or enhancing obstetric outcomes in the general IVF population. Similarly, ovulatory FET cycles do not offer advantages over artificial FET cycles for live birth or pregnancy loss, and current evidence remains conflicting for obstetric and perinatal outcomes. The route of progesterone administration in artificial FET cycles does not significantly affect live birth or pregnancy loss rates. FET approaches should be individualized based on patient characteristics and clinical context, and further research is necessary to optimize outcomes and inform best practices.