Euploidy rate is indpendently associated with the number of ova retrieved in a fresh donor cycles

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Studies have demonstrated that > 50% of human embryos are aneuploid following ovarian stimulation and IVF. Embryonic aneuploidy is correlated with maternal age. The reported aneuploidy rates range from 30% in women <30 years of age to >70% in women >40 years old (Munne et al., 2007). Experimental evidence also suggests that other treatment-related factors, including culture conditions, gamete manipulation, gamete aging and ovarian stimulation protocols may influence aneuploidy rates in human embryos. A recent study also reported that euploid blastocyst rates in cycles using donor eggs varied greatly between infertility clinics ranging from 39.5% to 82.5% (Munne et al., 2017). We examined the impact of the length of the ovarian stimulation, the number of ova retrieved, and the influence of the treating physician in fresh donor egg cycles from a single fertility center on: 1) the percentage of euploid blastocysts and 2) the frequency of blastocyst formation. A total of 161 consecutive fresh donor oocyte cycles performed between 2015 and 2016 were included in the study. The donors had a mean age of 25.1 +/- 3.5 years. A total of 1352 blastocysts were biopsied. The biopsies were analyzed in a single PGS laboratory using either high density oligonucleotide aCGH or NGS. The euploid and overall blastocyst rates were examined as a function of a) the length of the ovarian stimulation (stratified into three groups: < 8 =days (n=23), 9-11 days (n=117) and >12 days (n=21)); b) number of ova retrieved (stratified into three groups: < 20 eggs (n=35), 21-40 eggs (n=100), >41 eggs (n=26)); and c) between the four treating physicians. The euploid rate was calculated by dividing the number of euploid embryos by the number of biopsied blastocysts. Embryos with no diagnosis and/or degraded DNA (<2%) were excluded from this analysis. The percentage data were transformed by arcsine transformation and then analyzed using ANOVA and Tukey test. Differences with p<0.05 were considered significant in all comparisons. The euploid rates were 78.7%, 78.4% and 80.0% respectively when comparing by the length of ovarian stimulation, with no observed statistical differences (p=0.94). When analysed by the number of eggs retrieved, the euploid rates were: 73.2%, 79.9%, and 82.1%, respectively. A significant higher euploidy rate was observed in the group retrieved > 40 eggs (82.1%) compared to the group had < 20 eggs retrieved (p= 0.039). Four physicians managed the egg donor cycles with similar euploid rates of 74.6%, 79.7%, 81.2% and 78.4% (p=0.18). There were no significant differences observed in the percentage of blastocyst formation as a function of the length of ovarian stimulation (61.8%, 61.3%, and 61.8%, p=0.95), number of ova retrieved (61.5%, 61.2%, and, 63.3%, p=0.88) or treating physicians (57.6%, 66.5%, 62.3% and 67.0%, p=0.25). In donor ova cycles, the rate of euploid blastocysts was independently associated with the number of ova retrieved. The blasocysts formation frequency was not affected by the length of the ovarian stimulation, number of ova retrieved, or the treating physician.