Session 66: Embryo quality: does it predict pregnancy?

Abstract

Study question: In embryo selection, only the cytoplasm aspect of the cleavage (cytokinesis) is evaluated, neglecting the nuclei dynamics (fading before the cyto-kinesis and appearing afterwards) and karyokinesis (as nuclear division). Can the assessment of the nuclei dynamics improve embryo selection? Summary answer: The assessment of embryo cleavage by observing the nuclei dynamics strengthen the embryo scoring, since it is possible to distinguish big fragment from blastomeres and abnormal karyokinesis. What is known already: 4 blastomeres stage (4cells) and fragmentation ,20% are the key scoring parameters in embryo selection on day 2 transfer. The major objection concerning these parameters is the difficulty of visualizing the nucleus in each blastomere, and consequently distinguishing between blastomeres and big fragments. To overcome this problem, fragments are traditionally defined as extracellular membrane-bound cytoplasmic structures with a diameter ,45 mm. Time-lapse observation reveals the nucleus dynamics (nucleus fading before cytokinesis-nuclei reappearance after cytokinesis). Study design, size, duration: This prospective study included 362 transferred embryos cultured in time-lapse incubator, underwent ICSI in Holbaek Fertility Clinic from 20/05/2010 to 01/05/2012. Embryos were assessed at 45 hours post-fertilization (hPF) by single-observation. Embryos had fragmentation ≤25% and ≥4 blastomeres and they were reassessed by time-lapse multiple observations. Live-birth data were retrieved. Participants/materials, setting, methods: In time-lapse assessment, we observed the cytokinetic event in connection with the fading of parent cell nucleus and the appearing of sibling blastomere nuclei. Cleaved membrane-bound cytoplasmic structures were defined as fragments when no nucleus appeared, regardless size and single-observation assessment. Blastomeres cleaving in 3 nucleated cells were considered abnormal. Main results and the role of chance: According to single-observation selection, we transferred 286 embryos at 4cells, 56 at 5cells, 20 at 6-7cells. By time-lapse assessment, embryos were divided in 4 groups: Correct nuclei dynamics (CND); Blastomeres mistaken for fragments assessed (fragmentation ≤ 25% and blastomeres ≥ 4) (BMG); Blastomeres mistaken for fragments (fragmentation ≥ 25% and/or blastomeres ≤ 4) (BMB); Abnormal karyokinesis (AK). 4cells embryos were AK at 1% and BMB at 4%; 5cells embryos were AK at 32%, BMB at 4%, BMG at 43%. 6-7cells were AK at 25%, BMB at 25%, BMG at 20%. 5, 6-7cells embryos had more AK than 4cells (p. 0.0001). BMB + BMG were higher in 5 and 6-7cells than 4cells (p. 0.0001). Live-birth was achieved in CND at 4cells (27%) and 5cells (22%), in BMG at 4cells (22%). AK, BMB and 6-7cells resulted in no live-birth. Limitations, reason for caution: Single-observations at pre-set times for embryo scoring were performed by 5 embryologists. In contrary time-lapse observations were performed by a single operator, but later confirmed by a second operator. Embryo culture was performed only up to 45hPF. Wider implications of the findings: Our results are consistent with previous studies, showing a lower live-birth potential of embryos with .4 cells on day 2, suggesting nucleus dynamics abnormality and mis-observed fragments as underlying reasons. While new studies are suggesting the intervals of cleavage as selection parameters, our findings suggest that cytokinesis assessment needs to be combined with nucleus dynamics, for a more reliable embryo scoring, for avoiding transfer of abnormal embryos, with no live-birth potential. Study question: Can trophectoderm (TE) quality be a better predictor for selecting the best blastocyst in women of various maternal age groups? Summary answer: Blastocyst grading was not useful for predicting pregnancy among the patients who were less than 40 years of age. However, blastocyst grading, particularly TE grading, was a better method for selecting the best blasto-cyst among the patients who were more than 40 years of age. What is known already: Selecting the best blastocyst is important for success. For this selection, a morphological grading system has been widely used, which is based on the grading for three parameters: blastocoele expansion, size and com-pactness of the inner cell mass (ICM), and cohesiveness and number of TE cells. A recent report indicated that the predictive strength of TE grading was better than ICM for this selection. That report, however, did not focus on the maternal age. Study design, size, duration: This is a retrospective study between April 2009 and April 2012, for which 455 cycles of 200 patients who had undergone vitrified-warmed single blastocyst transfer in either the natural ovulatory cycle or hormone replacement cycle were recruited for this study. Participants/materials, setting, methods: All blastocysts were included in the following criteria described by Gardner: expansion grade was either 4 or 5, ICM grading was either A or B, and TE grading was also either A or B. The grading was expressed as ICM and TC consectively (AA, BA, AB or BB). Main results and the role of chance: The pregnancy rates of blastocyst grading AA, BA, AB, and BB for the patients who were more than 40 years of age were 61.9, 54.5, 38.7, and 17.6%, respectively. This rate for the grading of BB was significantly lower than that for either grades AA or BA. These results indicated that the pregnancy rates for grade B of TE tended to be lower than that of grade A of TE. The miscarriage rates in each of the grading classes were similar with no significant differences. Limitations, reason for caution: The evaluation of blastocyst grading was checked only once or twice during the culture. The results in the present study were confirmed by a consecutive checking system using time-lapse imaging. Wider implications of the findings: From the results, the pregnancy rates of AA, BA, AB, and BB for patients ,30 years of age were similar and there were no significant differences. The pregnancy rates of AA, BA, and AB tended to be higher than that of BB for patients 30-34 years of age, and this tendency was observed for the patients 35-39 years of age. However, there were no significant differences in the grading values in both age groups.