A systematic review of clinical efficacy of frozen-thawed embryos and fresh embryos in in-vitro fertilization cycles

Background: Frozen-thawed embryo (FTE) and fresh embryo (FE) transfer are two common strategies in vitro fertilization (IVF), while the results and findings still vary among studies. Methods: We searched multiple databases for relevant studies comparing the clinical effects of FTE and FE. Metaanalyses were conducted with Review Manager 5.0 to assess the efficacy among included articles. We also analyzed the risk of bias for the reports. Results: Nine studies eventually met the inclusion criteria from 2010 to 2018, and 11396 patients were included. The meta-analyses indicated no significant difference in biochemical pregnancy, clinical pregnancy and ongoing pregnancy rates. Meanwhile, the implantation rate and live birth rate in frozen-thawed embryos were much higher than those of fresh embryo. The birth weight in the frozen-thawed ET group was greater than that of the FE group, and the low birth weight rate in FTE was lower than FE group. Conclusion: Our findings suggested a trend toward favouring frozen-thawed FTE might be a preferred transfer strategy for patients with IVF.