Good-quality blastocysts derived from vacuolized morulas show reduced viability

Objective 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. Design Prospective observational study. Setting University teaching hospital. Patient(s) 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). Intervention(s) Screening for the presence of vacuoles on day 4 and fresh single-blastocyst transfer. Main Outcome Measure(s) Morula and blastocyst scoring, utilization rate, pregnancy and live birth rates. Result(s) Patients of group 1 had a reduced blastocyst formation rate on day 5 ( P P P P Conclusion(s) Late onset of vacuolization around compaction stage is a negative predictor of blastocyst formation and outcome.