A prospective randomized controlled trial investigating the effect of artificial shrinkage (collapse) on the implantation potential of vitrified blastocysts.

What is the effect of artificial shrinkage by laser-induced collapse before vitrification on the implantation potential after transfer of vitrified-warmed blastocysts? The artificial shrinkage by laser-induced collapse did not significantly increase the implantation rate per transferred collapsed blastocyst (37.6%) compared with non-collapsed blastocysts (28.9%) [odds ratio (OR): 1.48, 95% confidence interval (CI): 0.78-2.83]. Retrospective studies have demonstrated that artificial shrinkage of the blastocyst prior to vitrification can have a positive effect on blastocyst survival after warming. A recent study found a similar survival rate but higher implantation rate for collapsed blastocysts. So far, no randomized controlled trial has been conducted to investigate the implantation potential of collapsed blastocysts. Prospective randomized trial. Patients were recruited from December 2011 until April 2014 and warming cycles were included until July 2014. Patients were randomized in the fresh cycle if blastocysts were available for vitrification and were allocated to the study or control arm according to a computer-generated list. In the study group, blastocysts underwent laser-induced collapse before vitrification. In the control group, blastocysts were vitrified without collapsing. In total, 443 patients signed informed consent and 270 patients had blastocysts vitrified. One-hundred and thirty-five patients were allocated to the study group and 135 to the control group. Sixty-nine patients from the study group and 69 from the control group returned for at least one warming cycle in which 85 and 93 blastocysts were warmed in the first cycle, respectively. Primary outcome was implantation rate per embryo transferred in the first warming cycle. Secondary outcomes were survival and transfer rates, blastocyst quality after warming, clinical pregnancy rate and implantation rate per warmed blastocyst. Blastocysts were vitrified-warmed one by one using closed vitrification and one or two blastocysts were transferred per warming cycle. We calculated that the group sample sizes of 80 embryos in the collapse group and 80 embryos in the control group were needed to achieve 80% power to detect a difference between the group proportions of +20% with P < 0.05. In the study group, 69 first warming cycles resulted in 69 transfers with 1.2 blastocysts (n = 85) transferred. In the control group, an average of 1.3 blastocysts (n = 83) were transferred in 67 out of 69 warming cycles. Implantation rates per embryo transferred in the first warming cycle were not different between both groups (38 versus 29%, OR: 1.48; 95% CI: 0.78-2.83), neither was the implantation rate per warmed embryo (38 versus 26%, OR: 1.74; 95% CI: 0.92-3.29). When all warming cycles were considered (n = 135 in each group), survival rate after collapse was significantly higher compared with the control group (98.0 versus 92.0%, OR: 4.25; 95% CI: 1.19-15.21). Furthermore, a higher percentage of high-quality blastocysts (36.3 versus 23.5%, OR: 1.86; 95% CI: 1.12-3.08) and hatching blastocysts (19.2 versus 5.4%, OR: 4.18; 95% CI: 1.84-9.52) were found compared with the control group. The study lasted more than 2.5 years since fewer patients than expected returned for a warming cycle because of the high ongoing pregnancy rates in the fresh IVF/ICSI cycle. Although no significant higher implantation rate was found after collapse, the better survival and post-warm embryo quality convinced us to recognize a clinical benefit of artificial shrinkage and to implement it in routine vitrification practice. NCT01980225, www.clinicaltrials.gov. The first patient was included November 2011 and the study was registered October 2013.

Van Landuyt L ，Polyzos NP ，De Munck N ，Blockeel C ，Van de Velde H ，Verheyen G ... -  《-》

Associations of blastocyst features, trophectoderm biopsy and other laboratory practice with post-warming behavior and implantation.

Cimadomo D ，Capalbo A ，Levi-Setti PE ，Soscia D ，Orlando G ，Albani E ，Parini V ，Stoppa M ，Dovere L ，Tacconi L ，Ievoli E ，Maggiulli R ，Ubaldi FM ，Rienzi L ... -  《-》

Clinical outcomes following cryopreservation of blastocysts by vitrification or slow freezing: a population-based cohort study.

What are the clinical efficacy and perinatal outcomes following transfer of vitrified blastocysts compared with transfer of fresh or of slow frozen blastocysts? Compared with slow frozen blastocysts, vitrified blastocysts resulted in significantly higher clinical pregnancy and live delivery rates with similar perinatal outcomes at population level. Although vitrification has been reported to be associated with significantly increased post-thaw survival rates compared with slow freezing, there has been a lack of general consensus over which method of cryopreservation (vitrification versus slow freezing) is most appropriate for blastocysts. A population-based cohort of autologous fresh and initiated thaw cycles (a cycle where embryos were thawed with intention to transfer) performed between January 2009 and December 2011 in Australia and New Zealand was evaluated retrospectively. A total of 46 890 fresh blastocyst transfer cycles, 12 852 initiated slow frozen blastocyst thaw cycles and 20 887 initiated vitrified blastocyst warming cycles were included in the data analysis. Pairwise comparisons were made between the vitrified blastocyst group and slow frozen or fresh blastocyst group. A Chi-square test was used for categorical variables and t-test was used for continuous variables. Cox regression was used to examine the pregnancy outcomes (clinical pregnancy rate, miscarriage rate and live delivery rate) and perinatal outcomes (preterm delivery, low birthweight births, small for gestational age (SGA) births, large for gestational age (LGA) births and perinatal mortality) following transfer of fresh, slow frozen and vitrified blastocysts. The 46 890 fresh blastocyst transfers, 11 644 slow frozen blastocyst transfers and 19 978 vitrified blastocyst transfers resulted in 16 845, 2766 and 6537 clinical pregnancies, which led to 13 049, 2065 and 4955 live deliveries, respectively. Compared with slow frozen blastocyst transfer cycles, vitrified blastocyst transfer cycles resulted in a significantly higher clinical pregnancy rate (adjusted relative risk (ARR): 1.47, 95% confidence intervals (CI): 1.39-1.55) and live delivery rate (ARR: 1.41, 95% CI: 1.34-1.49). Compared with singletons born after transfer of fresh blastocysts, singletons born after transfer of vitrified blastocysts were at 14% less risk of being born preterm (ARR: 0.86, 95% CI: 0.77-0.96), 33% less risk of being low birthweight (ARR: 0.67, 95% CI: 0.58-0.78) and 40% less risk of being SGA (ARR: 0.60, 95% CI: 0.53-0.68). A limitation of this population-based study is the lack of information available on clinic-specific cryopreservation protocols and processes for slow freezing-thaw and vitrification-warm of blastocysts and the potential impact on outcomes. This study presents population-based evidence on clinical efficacy and perinatal outcomes associated with transfer of fresh, slow frozen and vitrified blastocysts. Vitrified blastocyst transfer resulted in significantly higher clinical pregnancy and live delivery rates with similar perinatal outcomes compared with slow frozen blastocyst transfer. Comparably better perinatal outcomes were reported for singletons born after transfer of vitrified blastocysts than singletons born after transfer of fresh blastocysts. Elective vitrification could be considered as an alternative embryo transfer strategy to achieve better perinatal outcomes following Assisted Reproduction Technology (ART) treatment. No specific funding was obtained. The authors have no conflicts of interest to declare.

Li Z ，Wang YA ，Ledger W ，Edgar DH ，Sullivan EA ... -  《-》

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 ... -  《-》

Testing an artificial intelligence algorithm to predict fetal heartbeat of vitrified-warmed blastocysts from a single image: predictive ability in different settings.

Could an artificial intelligence (AI) algorithm predict fetal heartbeat from images of vitrified-warmed embryos? Applying AI to vitrified-warmed blastocysts may help predict which ones will result in implantation failure early enough to thaw another. The application of AI in the field of embryology has already proven effective in assessing the quality of fresh embryos. Therefore, it could also be useful to predict the outcome of frozen embryo transfers, some of which do not recover their pre-vitrification volume, collapse, or degenerate after warming without prior evidence. This retrospective cohort study included 1109 embryos from 792 patients. Of these, 568 were vitrified blastocysts cultured in time-lapse systems in the period between warming and transfer, from February 2022 to July 2023. The other 541 were fresh-transferred blastocysts serving as controls. Four types of time-lapse images were collected: last frame of development of 541 fresh-transferred blastocysts (FTi), last frame of 467 blastocysts to be vitrified (PVi), first frame post-warming of 568 vitrified embryos (PW1i), and last frame post-warming of 568 vitrified embryos (PW2i). After providing the images to the AI algorithm, the returned scores were compared with the conventional morphology and fetal heartbeat outcomes of the transferred embryos (n = 1098). The contribution of the AI score to fetal heartbeat was analyzed by multivariate logistic regression in different patient populations, and the predictive ability of the models was measured by calculating the area under the receiver-operating characteristic curve (ROC-AUC). Fetal heartbeat rate was related to AI score from FTi (P < 0.001), PW1i (P < 0.05), and PW2i (P < 0.001) images. The contribution of AI score to fetal heartbeat was significant in the oocyte donation program for PW2i (odds ratio (OR)=1.13; 95% CI [1.04-1.23]; P < 0.01), and in cycles with autologous oocytes for PW1i (OR = 1.18; 95% CI [1.01-1.38]; P < 0.05) and PW2i (OR = 1.15; 95% CI [1.02-1.30]; P < 0.05), but was not significantly associated with fetal heartbeat in genetically analyzed embryos. AI scores from the four groups of images varied according to morphological category (P < 0.001). The PW2i score differed in collapsed, non-re-expanded, or non-viable embryos compared to normal/viable embryos (P < 0.001). The predictability of the AI score was optimal at a post-warming incubation time of 3.3-4 h (AUC = 0.673). The algorithm was designed to assess fresh embryos prior to vitrification, but not thawed ones, so this study should be considered an external trial. The application of predictive software in the management of frozen embryo transfers may be a useful tool for embryologists, reducing the cancellation rates of cycles in which the blastocyst does not recover from vitrification. Specifically, the algorithm tested in this research could be used to evaluate thawed embryos both in clinics with time-lapse systems and in those with conventional incubators only, as just a single photo is required. This study was supported by the Regional Ministry of Innovation, Universities, Science and Digital Society of the Valencian Community (CIACIF/2021/019) and by Instituto de Salud Carlos III (PI21/00283), and co-funded by European Union (ERDF, 'A way to make Europe'). M.M. received personal fees in the last 5 years as honoraria for lectures from Merck, Vitrolife, MSD, Ferring, AIVF, Theramex, Gedeon Richter, Genea Biomedx, and Life Whisperer. There are no other competing interests. N/A.

Conversa L ，Bori L ，Insua F ，Marqueño S ，Cobo A ，Meseguer M ... -  《-》