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

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; = 0.001), implantation rate (OR 2.44; = 0.002), clinical pregnancy rate (OR 3.04; = 0.001), ongoing pregnancy rate (OR 3.14; = 0.001), and live birth rate (OR 2.78; = 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; = 0.013) and implantation rate (OR 1.77; = 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.