In-vitro development of embryos derived from vitrified-warmed oocytes is delayed compared with embryos derived from fresh oocytes: a time-lapse sibling oocyte study.

Is there a difference in blastocyst formation between fresh and vitrified-warmed sibling oocytes and can this difference be attributed to changes in embryo morphokinetics? Between February 2016 and December 2017, 472 metaphase II (MII) oocytes in 67 donor-recipient cycles from 27 different healthy anonymous oocyte donors were allocated for fresh transfer (FSHO) (n = 220) to a synchronous recipient (n = 36) or vitrified (VITO) (n = 252) to be warmed and transferred to another recipient (n = 31). Embryos derived from the FSHO and their sibling VITO were analysed for morphokinetic development using time-lapse imaging, blastocyst formation and clinical outcome. Time-lapse analysis showed an overall delay in cleavage rate from the time of pronuclei disappearance up to the time of blastulation in the VITO compared with their sibling FSHO. Twelve morphokinetic variables were significantly different between the groups. On Day 5 significantly more FSHO embryos developed to blastocyst (expansion 1-6) and reached the full blastocyst stage (expansion 3-6) compared with the VITO embryos [53.2% (84/158) versus 40.0% (64/160); P = 0.0244 and 48.1% (76/158) versus 31.3% (50/160); P = 0.0028, respectively]. The embryo utilization rate was similar in both groups at the time of cryopreservation; 51.3% (FSHO) versus 45.0% (VITO) (P = 0.3124). The pregnancy rate per cycle was 47.2% (17/36) in FSHO patients and 48.4% (15/31) in VITO patients (P = 1). Limitations in this study: non-randomized, small study size and not powered to detect differences in clinical outcomes. Timing of development is altered and blastocyst formation is delayed in embryos derived from vitrified-warmed donor oocytes compared with their fresh sibling counterparts. Although preliminary results suggest that the clinical impact of this delay may be limited, this needs further investigation in larger randomized studies.

De Gheselle S ，De Sutter P ，Tilleman K 《-》

Pregnancy and birth outcomes following fresh or vitrified embryo transfer according to blastocyst morphology and expansion stage, and culturing strategy for delayed development.

How do live birth rates (LBRs), following fresh and vitrified/warmed embryo transfer, compare according to morphological grade, developmental stage and culturing strategy of human blastocysts in vitro? Equivalent LBRs were obtained after fresh embryo transfer and after vitrified/warmed embryo transfer of blastocysts of top or non-top quality, while vitrification after prolonged embryo culture of blastocysts with delayed development had a positive impact on LBR. Blastocyst morphology correlates with clinical outcome; however, few data are available on vitrified/warmed embryo transfer using non-top quality blastocysts. The aim of this study was to determine clinical outcomes of non-top quality blastocysts and blastocysts with delayed development that underwent vitrified/warmed embryo transfer. This retrospective, single-centre study (conducted January 2009 to June 2013) compared 1010 fresh embryo transfer and 1270 vitrified/warmed embryo transfer of blastocysts originating from the same stimulation cycle. Furthermore, 636 fresh embryo transfers and 304 vitrified/warmed embryo transfer after delayed expansion or blastulation in the same period were also analysed. Clinical outcomes after fresh and vitrified/warmed embryo transfer according to blastocyst morphology were compared in both groups. Similar LBRs after fresh embryo transfer or after vitrified/warmed embryo transfer of top or non-top quality blastocysts were observed. A statistically significant improvement in clinical outcomes was obtained after vitrified/warmed embryo transfer of Day 5 embryos with delayed expansion or blastulation when applying prolonged culture. Our study suggests that vitrification of non-top quality blastocysts as well as delayed cavitating and blastulating Day 5 embryos should be considered in autologous IVF cycles. Given that the present retrospective study used aseptic vitrification of blastocysts, the results, particularly the survival rates, may not be fully applicable to other vitrification protocols. The retrospective nature of the study has to be mentioned. Restriction of vitrification to top quality blastocysts may result in discarding potentially viable embryos. This study was not externally funded. There are no conflicts of interest to declare.

Wirleitner B ，Schuff M ，Stecher A ，Murtinger M ，Vanderzwalmen P ... -  《-》

Morphokinetics analysis of embryos derived from vitrified/warmed oocytes.

Montjean D ，Geoffroy-Siraudin C ，Gervoise-Boyer M ，Tourame P ，Boyer P ... -  《-》

Effect of oocyte vitrification on embryo quality: time-lapse analysis and morphokinetic evaluation.

To analyze whether oocyte vitrification may affect subsequent embryo development from a morphokinetic standpoint by means of time-lapse imaging. Observational cohort study. University-affiliated private IVF center. Ovum donation cycles conducted with the use of vitrified (n = 631 cycles; n = 3,794 embryos) or fresh oocytes (n = 1,359 cycles; n = 9,935 embryos) over 2 years. None. Embryo development was analyzed in a time-lapse imaging incubator. The studied variables included time to 2 cells (t2), 3 cells (t3), 4 cells (t4), 5 cells (t5), morula (tM), and cavitated, early, and hatching blastocyst (tB, tEB, tHB) as well as 2nd cell cycle duration (cc2 = t3 - t2). All of the embryos were classified according to the hierarchic tree model currently used for embryo selection. The analyzed variables were compared with the use of analysis of variance or chi-square and included 95% confidence intervals (CIs). The embryos that originated from vitrified oocytes showed a delay of ∼1 hour from the first division to 2 cells (t2) to the time of blastulation (tB). The embryos that originated from vitrified oocytes showed a delay of ∼1 hour from the 1st division to 2 cells (t2) to the time of blastulation (tB) (P<.05). The proportions of embryos allocated to categories A-E in the hierarchical tree were similar between groups. No differences in implantation rates between the fresh (51.3% [95% CI 47.1%-55.7%]) and vitrified (46.4% [95% CI 38.4%-54.4%]) groups were found. The embryo quality of vitrified oocytes was not impaired: cc2, quality according to our hierarchic morphokinetic model, and implantation rates were similar between fresh and vitrified oocytes. However, morphokinetic differences were observed from t2 to tB. Our main study limitation was the retrospective nature of the analysis, although a large database was studied.

Cobo A ，Coello A ，Remohí J ，Serrano J ，de Los Santos JM ，Meseguer M ... -  《-》

How does vitrification affect oocyte viability in oocyte donation cycles? A prospective study to compare outcomes achieved with fresh versus vitrified sibling oocytes.

Solé M ，Santaló J ，Boada M ，Clua E ，Rodríguez I ，Martínez F ，Coroleu B ，Barri PN ，Veiga A ... -  《-》