Freeze-all cycle in reproductive medicine: current perspectives

Abstract

The freeze-all strategy has emerged as an alternative to fresh embryo transfer (ET) during in vitro fertilization (IVF) cycles. Although fresh ET is the norm during assisted reproductive therapies (ART), there are many concerns about the possible adverse effects of controlled ovarian stimulation (COS) over the endometrium. The supra-physiologic hormonal levels that occur during a conventional COS are associated with modifications in the peri-implantation endometrium, which may be related to a decrease in pregnancy rates and poorer obstetric and perinatal outcomes when comparing fresh to frozen-thawed embryo transfers. The main objective of this study was to assess the available literature regarding the freeze-all strategy in IVF cycles, in regards to effectiveness and safety. Although there are many potential advantages in performing a freeze-all cycle over a fresh ET, it seems that the freeze-all strategy is not designed for all IVF patients. There is a need to develop a non-invasive clinical tool to evaluate the endometrial receptivity during a fresh cycle, which enables the selection of patients that would benefit from this strategy. Today, it is reasonable to perform elective cryopreservation of all oocytes/embryos in cases with a risk of OHSS development, and in patients with supra-physiologic hormonal levels during the follicular phase of COS. It is not clear if all normal responders and poor responders may benefit from this strategy.

Does freeze‐all policy affect IVF outcome in poor ovarian responders?

“…Fresh embryo transfer (ET) is still the standard procedure for in-vitro fertilization (IVF) treatments, although recent scientific data have shown the potential benefit of performing cycle segmentation with deferred ET, known as the freeze-all policy [2][3][4][5][6] . It is unknown whether this strategy can be used for all patients, irrespective of their ovarian response and hormone levels during controlled ovarian stimulation (COS) [7][8][9][10][11] .…”

Elective freeze-all embryos: What is the scientific evidence?

“…The new analysis included 259 IVF cycles with blastocyst embryo transfers in normal and high responders; nonetheless, they found that FTET had a 31 per cent higher clinical pregnancy rate than FET. 5 however, time to pregnancy was not reported in any study. Additionally, they suggested that FTET lowered the OHSS risk for at-risk women with low-quality evidence (OR 0.24, 95 per cent CI 0.15-0.38; 1633 women; I 2 = 0 per cent; lowquality evidence).…”

“…Although evidence of FTET after electively freezing all embryos has been suggested to have good outcomes through basic and clinical research, the results of recent clinical studies still challenge the scientific dogma. 3,5,6 Methods A through literature search was conducted in PubMed to gather the published articles comparing clinical outcomes of FTET and FET. The following keywords were used: 'frozenthawed embryo transfer', 'fresh embryo transfer', 'cryopreserved-thawed embryo transfer', 'freeze all policy', from their inceptions through July 2017.…”

Laser collapse performance in blastocysts applied before vitrification

“…Research Article Laser collapse performance in blastocysts applied before vitrification Based on these facts, many centers have chosen to freeze all embryos to transfer them in a next cycle, method known as "Freeze-all strategy". 1,5,7,9 The first pregnancy obtained by transfer of frozen and thawed embryos was reported by Trouson and Mohr in 1983 and since then, the cryopreservation of embryos has been used as standard procedure in human reproduction clinics. [10][11][12] Thus, three main methods of cryopreservation have been employed: slow freezing, ultra fast freezing and vitrification.…”

“…However, the success of embryo implantation and decrease of perinatal morbidity depends not only on its quality, but also on the receptivity of the endometrium as well as the maternal microenvironment and embryonic signaling with the uterine cavity. 1,2 In IVF centers, more and more specialists have shifted to transference of frozen embryos (TEC), instead of fresh transfer. [3][4][5] This is due to the fact that the transfer of fresh embryos in patients with ovarian hyperstimulation syndrome (OHSS) can lead to death risk for the patient.…”