Abstract
Societal changes and the increasing desire and opportunity to preserve fertility have increased the demand for effective assisted reproductive technologies (ART) and have increased the range of scenarios in which ART is now used. In recent years, the “freeze-all” strategy of cryopreserving all oocytes or good quality embryos produced in an IVF cycle to transfer later—at a time that is more appropriate for reasons of medical need, efficacy, or desirability—has emerged as an accepted and valuable alternative to fresh embryo transfer. Indeed, improvements in cryopreservation techniques (vitrification) and the development of more efficient ovarian stimulation protocols have facilitated a dramatic increase in the practice of elective frozen embryo transfer (eFET). Alongside these advances, debate continues about whether eFET should be a standard treatment option available to the whole IVF population or if it is important to identify patient subgroups who are most likely to benefit from such an approach. Achieving successful outcomes in ART, whether by fresh or frozen embryo transfer, is influenced by a wide range of factors. As well as the efficiency of IVF and embryo transfer protocols and techniques, factors affecting implantation include maternal aging, sperm quality, the vaginal and endometrial microbiome, and peri-implantation levels of serum progesterone. The safety of eFET, both during ART cycles and on longer-term obstetric and neonatal outcomes, is also an important consideration. In this review, we explore the benefits and risks of freeze-all strategies in different scenarios. We review available evidence on the outcomes achieved with elective cryopreservation strategies and practices and how these compare with more traditional IVF cycles with fresh embryo transfers, both in the general IVF population and in subgroups of special interest. In addition, we consider how to optimize and individualize “freeze-all” procedures to achieve successful reproductive outcomes.
Highlights
Increasing demand for assisted reproductive technologies (ART) and improvements in cryopreservation techniques are re-shaping the therapeutic landscape in fertility treatment
The LBR benefit was only evident in hyper-responders and in preimplantation genetic testing (PGT)-A cycles (RR, 1.55; 95% CI, 1.14–2.10)
Beyond the potential risks associated with artificial cycle fresh embryo transfer in high responders, these findings suggest that in this population, there might be an impairment of endometrial receptivity due to a direct impact of high steroid levels, mainly progesterone, on endometrial maturation [47, 124]
Summary
Increasing demand for assisted reproductive technologies (ART) and improvements in cryopreservation techniques are re-shaping the therapeutic landscape in fertility treatment. Changes in and increased use of ART protocols and procedures have been fueled recently by the development of more efficient ovarian stimulation protocols—for example, modified luteal phase support after gonadotrophin-releasing hormone (GnRH) agonist triggers in GnRH antagonist protocols [1]—and new methods of cryopreservation (vitrification) as an alternative to the more traditional method of slow freezing [2, 3]. These advances, alongside growing understanding of the factors that can affect the outcomes of ART, are leading to continuing improvement in reproductive outcomes. Pioneers of elective cryopreservation and postponed embryo transfer applied the term “segmentation” of in vitro fertilization (IVF) treatments, where ovarian stimulation and oocyte/embryo retrieval is disconnected from the subsequent process of embryo transfer [14]; a newer term that perhaps better represents the entire process is elective frozen embryo transfer (eFET) [15]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
