Embryos from vitrified vs. fresh oocytes in an oocyte donation program: a comparative morphokinetic analysis.

OBJECTIVE: To compare the morphokinetic patterns of human embryos originating from vitrified oocytes (VITRI group) with those derived from freshly collected oocytes (CONTROL group) in oocyte donation cycles. DESIGN: This is a retrospective observational study. SETTING: Embryolab Fertility Clinic, Embryology Lab, Thessaloniki, Greece. PATIENT(S): The study included embryos from 421 vitrified oocytes from 58 oocyte donation cycles and 196 fresh oocytes from 23 oocyte donation cycles. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Key time parameters, dynamic events, fertilization rates, degeneration rates, cleavage rates, blastocyst rates, pregnancy rates, clinical pregnancy rates, implantation rates, and live birth rates were estimated. RESULTS: The mean survival rate of vitrified oocytes was 92.58% (±7.42%). Fertilization rates were significantly different between the 2 groups (VITRI group: 71.92% ± 20.29% and CONTROL group: 80.65% ± 15.22%) whereas the degeneration, cleavage, blastocyst, pregnancy, clinical pregnancy, ongoing pregnancy, implantation, and live birth rates were not significantly different between embryos derived from fresh or vitrified oocytes. Time-lapse analysis showed no significant difference in any key time parameter. However, when examining dynamic parameters, first cell cycle (CC1) (t2 - tPB2: from the second polar body extrusion (tPB2) up to 2 cells (t2)) showed a significant difference whereas CC1a (t2 - tPNf: from fading of the pronuclei (tPNf) up to 2 cells (t2)) was at the threshold of significance. CONCLUSION(S): CC1 in vitrified oocytes exhibited a comparatively slower progression in contrast to fresh oocytes. Conversely, CC1a in vitrified oocytes demonstrated faster progression compared with fresh oocytes. It is worth noting that these temporary deviations had minimal impact on the subsequent development. Despite the clinical outcomes showing a decrease in the vitrified group, none of them reached statistical significance. This lack of significance could be attributed to the limited sample size of the study.

Double vitrification of embryos adversely affects clinical outcomes.

OBJECTIVE: To evaluate the impact of double embryo vitrification on clinical outcomes. METHODS: This retrospective cohort study included data from January 2013 to March 2021. The study group included women aged 33.3±5.7 years with double-vitrified embryos (n=381), while the control group included women aged 32.1±6.7 years with embryos vitrified once (n=780), all transferred at the blastocyst stage. The primary endpoint was live birth rate (LBR), and secondary endpoints included percent positive ßHCG test, clinical/ongoing pregnancy rates, miscarriage/biochemical pregnancy rates and birthweight. RESULTS: LBR was significantly lower in double-vitrified embryos (30.2%) than in embryos vitrified once (45.6%, p<.05). Similarly, double-vitrified embryos were associated with significantly lower positive ßHCG tests (46% vs. 63.3%, p<.05) and clinical (34.9% vs. 52.2%, p<.05) and ongoing pregnancy (31.3% vs. 47.3%, p<.05) rates compared to embryos vitrified once. However, biochemical pregnancy (double vitrified: 24.1% vs. vitrified once: 17.9%, p>.05) and miscarriage rates (double vitrified: 10.2% vs. vitrified once: 9.4%, p>.05), as well as mean birthweight (double-vitrified embryos: 2950g vs. embryos vitrified once: 2837g, p>.05) did not differ significantly between two groups. On a secondary comparison, amongst double-vitrified embryos, the subgroup that was cultured for more than 24 hours between warming and second vitrification achieved significantly higher positive ßHCG tests (49%) and clinical pregnancy (38%) rates, compared to embryos re-vitrified on the same day of warming (31.8% and 20.5%, respectively, p<.05). Nevertheless, LBR did not differ significantly amongst these study-group embryos (embryos that remained in culture for more than 24 hours: 32.2% vs. embryos that were re-vitrified on warming day: 20.5%, p>.05). CONCLUSIONS: Double vitrification of embryos adversely affects clinical outcomes. However, it represents a valuable option concerning embryo wastage, with acceptable success rates.

The impact of fresh and frozen testicular tissue quality on embryological and clinical outcomes.

Our ability to predict the potential of testicular spermatozoa to support embryonic development is still limited. Although motility of testicular spermatozoa is associated with embryo development, the impact of morphology and the presence of spermatozoa in the testicular sample has not been previously researched. Moreover, while the majority of data indicate no effect of cryopreservation, there are studies reporting impaired clinical outcomes due to testicular cryopreservation. In a retrospective study, 118 ICSI-TESE cycles were analysed to study the impact of (a) total quality of testicular tissue, (b) testicular tissue cryopreservation and (c) presence/motility/morphology of testicular spermatozoa in fertilisation rate, embryonic development, clinical pregnancy (CPR), ongoing pregnancy (OPR) and live birth rate (LBR). Results showed that fertilisation rate was significantly affected by both total quality of testicular tissue (p < .05) and rare presence of spermatozoa (p < .01). Moreover, total tissue quality (p < .01), cryopreservation of low-quality samples (p < .01), absence of motile testicular spermatozoa (p < .01) and poor spermatozoa morphology (p < .05) had a negative impact on the number of good quality day 3 embryos. CPR, OPR or LBR was not affected by any parameters examined. Our data suggest that the quality of testicular tissue influences both fertilisation rate and embryo development. Moreover, cryopreservation of low-quality testicular samples has a negative impact on the number of available embryos for transfer.