Reduced live birth rate after frozen compared to fresh single poor cleavage-stage embryo transfer cycles: a retrospective study

Abstract Purpose The ongoing debate focuses on whether the freeze-all strategy is suitable for the general population or may be offered to specific subgroups of patients. This study aimed to compare the pregnancy and neonatal outcomes between FET and fresh ET and evaluate the effectiveness of the embryo freezing strategy for a specific group of patients undergoing single poor cleavage-stage embryo transfer. Methods A total of 1,819 ET cycles that underwent single poor cleavage-stage embryo transfer between January 2014 and December 2020 were enrolled in this study and categorized into two groups according to the embryo processing methods: fresh ET group (n = 1124) and frozen ET group (n = 695). Results We found that the clinical pregnancy and live birth rates were significantly higher in the fresh cycles than in the frozen cycles (32.38% vs. 22.30%, p = 0.000; 25.62% vs. 16.12%, p = 0.000, respectively). The multivariate logistic regression model showed that the cycle type (fresh or frozen) still had a significant impact on the live birth rate (OR 1.62, 95% CI: 1.19–2.21, p = 0.002) after adjusting for potential confounders. Discussion FET was associated with a significantly lower risk of clinical pregnancy and live birth rates. For patients who are more likely to develop poor-quality cleavage embryos, such as women with previous low response or reduced ovarian reserve, it is suggested that fresh ET should be given priority to achieve better pregnancy and neonatal outcomes than FET if there are no special circumstances.