Freeze-all policy for in vitro fertilization in women with normal response to ovarian stimulation.

Oscar Barbosa Duarte-Filho,Sérgio Podgaec

doi:10.31744/einstein_journal/2021ao6290

Oscar Barbosa Duarte-Filho, Sérgio Podgaec

Open Access

https://doi.org/10.31744/einstein_journal/2021ao6290

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Abstract

ABSTRACTObjective To answer the question if the freeze-all strategy and subsequent frozen embryo transfer is preferable to fresh embryo transfer for patients with normal response to ovarian stimulation (4 to 15 oocytes recovered) during in vitro fertilization treatments.Methods A retrospective cohort from two human reproduction centers between 2013 and 2017. A total of 471 frozen embryo transfers from freeze-all cycles, and 3,208 fresh transfers were included.Results After propensity score matching adjustment for age and number of eggs, 467 freeze-all cycles and 934 fresh cycles were analyzed, revealing no statistically significant difference between groups in relation to clinical pregnancy rate (32.5% in the Freeze-all Group and 32.3% in the Fresh Group, p=0.936). For women aged 40 years and older, we observed a statistically significant higher clinical pregnancy rate when freeze-all strategy was used (29.3% in the Freeze-all Group and 19.8% in the Fresh Group, p=0.04).Conclusion Freeze-all strategy was not superior to fresh transfer for all patients with normal response to ovarian stimulation. However, women aged 40 years and older could benefit from this strategy. This deserves further investigation in future research, preferable in a prospective randomized study.

Highlights

The first human birth from in vitro fertilization (IVF) occurred from a fresh-embryo transfer, in England, in 1978.(1) Five years later, an Australian group reported the first birth after frozen embryo replacement.[2]. Since more than seven million babies have been born through IVF with fresh or frozen embryo transfer.[3]
During the early era of IVF, fresh-embryo transfer was the standard of care, because results following embryo freezing by the slow cooling technique were unsatisfactory.[4]. Frozen transfers were restricted to surplus embryos and where fresh transfer was not possible, which was the case mostly in patients with a high response to controlled ovarian stimulation, and at risk of ovarian hyperstimulation syndrome.[5]
Two facts have changed the practice of fresh transfers: the demonstration that replacement of fresh embryos into the endometrium, while under the effects of drugs for ovarian stimulation can alter endometrium receptivity,(7) and the development of vitrification methods for human embryos-ultra-fast freezing that is simpler, has better survival and pregnancy results compared with slow cooling.[8]. These factors have led to a growing debate as to whether the standard of care should shift from the current “freeze-all for selected patients” to a “freeze-all for all” approach.[9,10,11]

Summary

Introduction

The first human birth from in vitro fertilization (IVF) occurred from a fresh-embryo transfer, in England, in 1978.(1) Five years later, an Australian group reported the first birth after frozen embryo replacement.[2]. During the early era of IVF, fresh-embryo transfer was the standard of care, because results following embryo freezing by the slow cooling technique were unsatisfactory.[4] Frozen transfers were restricted to surplus embryos and where fresh transfer was not possible, which was the case mostly in patients with a high response to controlled ovarian stimulation, and at risk of ovarian hyperstimulation syndrome.[5]. Two facts have changed the practice of fresh transfers: the demonstration that replacement of fresh embryos into the endometrium, while under the effects of drugs for ovarian stimulation can alter endometrium receptivity,(7) and the development of vitrification methods for human embryos-ultra-fast freezing that is simpler, has better survival and pregnancy results compared with slow cooling.[8] These factors have led to a growing debate as to whether the standard of care should shift from the current “freeze-all for selected patients” to a “freeze-all for all” approach.[9,10,11]. Two recent meta-analyses found similar pregnancy rates between the two strategies for patients with normal response to ovulation stimulation, but there is much heterogeneity among the studies, and the evidence to support this strategy is still considered of low-quality.[12,13]

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Conclusion