Clinical Outcome of Day-3 Cleavage Slow-Growing Embryos at Different Cleavage Rates after Overnight Culture: A Cohort Retrospective Study.

ABSTRACT

INTRODUCTION: We explored the association between clinical outcomes and the cleavage rate of day-3 cleavage slow-growing embryos after overnight culture. METHODS: The data collected from 303 frozen embryo transfer (FET) cycles with 606 4-cell or 5-cell embryos cultured overnight (18-22 h) after thawing were analyzed. Based on the growth rate after the overnight culture, the embryos were divided into three groups no embryo reaching eight cells (Group I), either one of the two embryos reaching eight cells (Group II), and both two embryos reaching eight cells or more (Group III). A statistical analysis of the different clinical outcomes from the three groups was performed. RESULTS: Biochemical pregnancy rate (OR 3.22; p = 0.001), implantation rate (OR 2.44; p = 0.002), clinical pregnancy rate (OR 3.04; p = 0.001), ongoing pregnancy rate (OR 3.14; p = 0.001), and live birth rate (OR 2.78; p = 0.004) were significantly higher in Group III as compared to Group I. Group II had a significantly higher biochemical pregnancy rate (OR 2.02; p = 0.013) and implantation rate (OR 1.77; p = 0.019) than Group I. CONCLUSIONS: The capability of day-3 cleavage slow-growing embryos to reach eight cells, especially that of two embryos reaching eight cells by overnight culture, appear to result in a better pregnancy outcome.