Fresh versus elective frozen embryo transfer: Cumulative live birth rates of 7,236 IVF cycles.

OBJECTIVE: To determine whether elective frozen embryo transfer (eFET), or the 'freeze-all' strategy, associated with better cumulative clinical outcomes compared with fresh embryo transfer (ET). METHODS: A total of 7,236 IVF cycles that were followed by a fresh ET or eFET between 2013 and 2017. The patients were subjected to controlled ovarian stimulation (COS) with a gonadotropin-releasing hormone (GnRH) antagonist protocol and cleavage-stage ET. Embryo cryopreservation was performed on day 3 by vitrification using an open system. A comparison of cumulative outcomes between the eFET (n=4,065cycles) and the fresh ET groups (n=3,171cycles) were performed. The analysis was performed in four groups of patients based on the number of retrieved oocytes: Group 1: poor responders (1-3 oocytes); Group 2: suboptimal responders (4-9 oocytes); Group 3: normal responders (10-15 oocytes); and Group 4: hyper-responders (>15 oocytes). The primary outcome was the cumulative live birth rate (CLBR) per stimulated cycle. RESULTS: There were a total of 10,283 ETs (n=5,639 eFET group; n=4,644 fresh group). The freeze-all strategy is associated with improved CLBRs in normal and hyper-responders, but not in suboptimal and poor responders. In Group 1, there were 351 IVF cycles and 387 ETs in total, and the CLBR was 14.3% and 17.7% (p=0.584) for the eFET and fresh group, respectively. In Group 2, there were 2,074 IVF cycles and 2,465 ET in total, and the CLBR was 25.1% and 23.3% (p=0.083) in the eFET and fresh group, respectively. There was a significant difference in the CLBR in Groups 3 and 4, favouring the eFET strategy. In Group 3, 2226 IVF cycles and 3243 ET were performed. The CLBR was 40.5% in the eFET and 36.6% in the fresh group (p<0.001). In Group 4, there were 2547 IVF cycles and 3,188 ET in total, and the CLBR was 52.2% and 47.7% (p<0.001) in the eFET and fresh group, respectively. The number needed to treat to achieve one additional live birth was 25.9 in Group 3 and 22.3 in Group 4. CONCLUSIONS: The implementation of the freeze-all strategy should be individualized. The freeze-all strategy is associated with improved CLBRs in normal and hyper-responders, but not in suboptimal and poor responders.

Freeze-all cycle in reproductive medicine: current perspectives.

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.

Freeze-all cycle for all normal responders?

PURPOSE: The purpose of this study is to evaluate the freeze-all strategy in subgroups of normal responders, to assess whether this strategy is beneficial regardless of ovarian response, and to evaluate the possibility of implementing an individualized embryo transfer (iET) based on ovarian response. METHODS: This was an observational, cohort study performed in a private IVF center. A total of 938 IVF cycles were included in this study. The patients were submitted to controlled ovarian stimulation (COS) with a gonadotropin-releasing hormone (GnRH) antagonist protocol and a cleavage-stage day 3 embryo transfer. We performed a comparison of outcomes between the fresh embryo transfer (n = 523) and the freeze-all cycles (n = 415). The analysis was performed in two subgroups of patients based on the number of retrieved oocytes: Group 1 (4-9 oocytes) and Group 2 (10-15 oocytes). RESULT(S): In Group 1 (4-9 retrieved oocytes), the implantation rates (IR) were 17.9 and 20.5% (P = 0.259) in the fresh and freeze-all group, respectively; the ongoing pregnancy rates (OPR) were 31 and 33% (P = 0.577) in the fresh and freeze-all group, respectively. In Group 2 (10-15 oocytes), the IR were 22.1 and 30.1% (P = 0.028) and the OPR were 34 and 47% (P = 0.021) in the fresh and freeze-all groups, respectively. CONCLUSION(S): Although the freeze-all policy may be related to better in vitro fertilization (IVF) outcomes in normal responders, these potential advantages decrease with worsening ovarian response. Patients with poorer ovarian response do not benefit from the freeze-all strategy.