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

Abstract

To compare the morphokinetic pattern of human embryos originating from vitrified oocytes with those derived from freshly collected oocytes in oocyte donation cycles. 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. None MAIN OUTCOME MEASURE(S): Key time parameters, dynamic events, fertilization rate, degeneration rate, cleavage rate, blastocyst rate, pregnancy rate, clinical pregnancy rate, implantation rate and live birth rate. Survival rate of vitrified oocytes was 92.58% (±7.42). Fertilization rate was significantly different in the two groups (VITRI group: 71.92% ± 20.29 and CONTROL group: 80.65% ± 15.22, p=0.045) whereas 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, CC1 [t2 - tPB2: from the second polar body extrusion(tPB2) up to 2 cells (t2)] showed significant difference (p=0.004) whereas CC1a [t2 - tPNf: from fading of the pronuclei (tPNf) up to 2 cells (t2)] was at the threshold of significance (p=0.057). CC1 in vitrified oocytes exhibited a comparatively slower progression in contrast to fresh oocytes. Conversely, CC1a in vitrified oocytes demonstrated faster progression compared to fresh oocytes. Noteworthily, 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 study's size.