Good-quality blastocysts derived from vacuolized morulas show reduced viability - Fertility and Sterility

To study whether late spontaneous vacuolization on day 4 is an artefact or an alternate means of blastocele formation and to analyze its impact on pregnancy outcome and live birth. Prospective observational study. University teaching hospital. A total of 424 patients who fulfilled inclusion criteria were subgrouped according to the spontaneous vacuolization on day 4: Group 1 had all morulas affected, group 2 showed no signs of vacuoles, and group 3 was mixed (some day 4 embryos had vacuoles and others did not). Screening for the presence of vacuoles on day 4 and fresh single-blastocyst transfer. Morula and blastocyst scoring, utilization rate, pregnancy and live birth rates. Patients of group 1 had a reduced blastocyst formation rate on day 5 (P<.01) and significantly fewer good-quality blastocysts for usage (P<.05). In addition, pregnancy (P<.001) and live birth (P<.01) rate were significantly worse in group 1 compared with groups 2 and 3. Late onset of vacuolization around compaction stage is a negative predictor of blastocyst formation and outcome.