Sequential embryo scoring system can substitute for time lapse monitoring system

Abstract

Time lapse scoring system has an advantage in selecting the best embryo by evaluating embryo's continuous development at certain time points. In our laboratory, we investigated if the sequential embryo-scoring system could exhibit positive effects in selecting embryos by replacing the time-lapse function with cleavage stage embryos, including early-cleavage at certain time points. All fresh, non-donor IVF cycles performed from January 2015 through August 2015 (n=485). After insemination, embryos were scored at the following 3 time points: 2-cell cleavage (26h), day 2 (40-41h), and day 3 (64-65h). The highest score of the embryo at 3 time points is as follows: 2-cell cleavage (2 points) + day 2 (5 points) + day 3 (5 points) = 12 points. In two embryos transfer, the highest total score is 24 points. The score was dependent on three factors: (number of blastomere, synchrony of cleavage, level of fragmentation). Scoring was done by subtracting scores from embryos with one or more defects. To determine a cut-off value, pregnancy rate was evaluated in one point unit from 6 points to 24 points based on two embryos transfer. Based on the cut-off value, embryos were divided into two groups, and the pregnancy and implantation rate were checked. The cut-off value was 16 points, and it was confirmed that pregnancy rate significantly improved. When the two groups (group (1) scored higher than 16 points, group (2) scored less than 15 points) based on the cut-off value were divided and compared. Patient characteristics were similar in the 2 groups. In each group, age (Group 1: 35.6±2.0 vs. Group 2: 36.0±1.9) basal AMH conc. (4.2±2.9 vs. 4.8±2.8ng/ml), and endometrial thickness (10.2±2.2 vs. 10.1±2.0mm) did not show significant differences. There were no significant differences between 2 groups in the number of MII oocytes (10.6±6.0 vs. 10.6±5.3) and number of embryo transfer (2.0±0.1 vs. 2.0±0.1). Group (1) had a significantly high pregnancy rate (68.8%, P=0.001) and implantation rate (57.1%, P=0.001) compared to that of Group (2) (41.6% and 31.6%, respectively). Our study evaluated the continuous development process of the embryo through the sequential embryo scoring system. We found that embryos with scores higher than 16 points resulted in a significantly high pregnancy rate. Therefore, the sequential embryo scoring system is effective in predicting high pregnancy rates.