Vitrified-warmed Blastocyst Research Articles

Exogenous progesterone rescue in patients with low mid-luteal serum progesterone levels undergoing true natural vitrified-warmed blastocyst transfer.

To explore whether a 25mg subcutaneous progesterone daily rescue daily improves the reproductive outcomes in patients with low serum progesterone (P4) levels (7-10ng/mL), measured one day before true natural cycle (t-NC) frozen embryo transfer (FET). A cohort study of 192 women undergoing t-NC warmed blastocyst transfer. Patients were stratified into three different groups based on serum P4 levels on the FET-1day: patients who had serum P4 levels of 7-10ng/mL and underwent rescue progesterone administration (rescue group), patients with serum P4 levels of 7-10ng/mL without progesterone administration (non-rescue group), and patients with serum P4 > 10ng/mL on FET-1day (control group). The primary outcome was possible differences in live birth rate (LBR) between groups. The LBRs for the serum P4 7-10ng/mL without rescue, 7-10ng/mL with rescue, and > 10ng/mL (control) groups were 41%, 46%, and 52%, respectively (p = 0.61). The estimated adjusted probability of live birth for serum P4 7-10ng/mL without rescue, 7-10ng/mL with rescue, and > 10ng/mL (control) groups were also comparable: 43.5% (95% CI, 20.0-70.4%), 49.8% (95% CI, 28.1-71.6%), and 57.4% (95% CI, 44.0-69.8%), respectively. Serum P4 levels higher than 7ng/mL seem to secure LBRs in patients undergoing t-NC FET. A rescue policy consisting of a daily subcutaneous 25mg progesterone dose in patients with serum P4 levels 7-10ng/mL does not further enhance LBRs when compared to those patients with similar serum P4 levels without rescue.

Elevated luteinizing hormone levels during the artificial endometrial preparation cycle do not impact pregnancy outcomes in patients undergoing single vitrified-warmed blastocyst transfer

The effect of an increase in luteinizing hormone levels on pregnancy outcomes in patients undergoing artificial endometrial preparation for frozen embryo transfer has not been definitively elucidated. We aimed to investigate the effect of elevated luteinizing hormone levels, measured prior to progesterone administration, on the ongoing pregnancy rate in patients undergoing artificial endometrial preparation for single vitrified-warmed blastocyst transfer. Patients began taking oral oestradiol valerate on menstrual day 2–3. When the endometrial thickness reached ≥7 mm, they were tested for oestradiol, progesterone, and luteinizing hormone, and luteal phase support was started. The participants were divided into four groups based on luteinizing hormone percentiles, and differences in pregnancy outcomes were examined. No significant differences were observed for on-going pregnancy rate and the other pregnancy outcomes between the groups. In multivariate logistic regression analysis, not the luteinizing hormone levels but the quality of embryo had a significant influence on ongoing pregnancy (p = 0.004; adjusted odds ratio, 1.8; 95% confidence interval, 1.213–2.675). The elevation of luteinizing hormone levels during artificial endometrial preparation did not have an impact on the ongoing pregnancy or the other pregnancy outcomes.

Identifying key predictive features for live birth rate in advanced maternal age patients undergoing single vitrified-warmed blastocyst transfer

BackgroundInfertility affects one in six couples worldwide, with advanced maternal age (AMA) posing unique challenges due to diminished ovarian reserve and reduced oocyte quality. Single vitrified-warmed blastocyst transfer (SVBT) has shown promise in assisted reproductive technology (ART), but success rates in AMA patients remain suboptimal. This study aimed to identify and refine predictive factors for live birth following SVBT in AMA patients, with the goal of enhancing clinical decision-making and enabling personalized treatment strategies.MethodsThis retrospective cohort study analyzed 1,168 SVBT cycles conducted between June 2016 and December 2022 at the First Affiliated Hospital of Guangxi Medical University and Nanning Maternity and Child Health Hospital. Nineteen machine-learning models were applied to identify key predictive factors for live birth. Feature selection and 10-fold cross-validation were employed to validate the models.ResultsThe most significant predictors of live birth included inner cell mass quality, trophectoderm quality, number of oocytes retrieved, endometrial thickness, and the presence of 8-cell blastomeres on day 3. The stacking model demonstrated the best predictive performance (AUC: 0.791), followed by Extra Trees (AUC: 0.784) and Random Forest (AUC: 0.768). These models outperformed traditional methods, achieving superior accuracy, sensitivity, and specificity.ConclusionLeveraging advanced machine-learning models and identifying critical predictive factors can improve the accuracy of live birth outcome predictions for AMA patients undergoing SVBT. These findings offer valuable insights for enhancing clinical decision-making and managing patient expectations. Further research is needed to validate these results in larger, multi-center cohorts and to explore additional factors, including fresh embryo transfers, to broaden the applicability of these models in clinical practice.

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.

Transcriptomic Analysis of Vitrified-Warmed vs. Fresh Mouse Blastocysts: Cryo-Induced Physiological Mechanisms and Implantation Impact.

Blastocyst vitrification has significantly improved embryo transfer methods, leading to higher implantation success rates and better pregnancy outcomes in subsequent frozen embryo transfer cycles. This study aimed to simulate the transcriptional changes caused by vitrifying human blastocysts using mouse blastocysts as a model and to further investigate these changes' effects. Utilizing a human vitrification protocol, we implanted both vitrified and fresh embryos into mice. We observed the implantation success rates and performed transcriptomic analysis on the blastocysts. To validate the results from messenger RNA sequencing, we conducted reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) to measure the expression levels of specific genes. Based on mRNA profiling, we predicted the microRNAs responsible for the regulation and used qPCR basic microRNA assays for validation. Our observations revealed a higher implantation success rate for vitrified embryos than fresh embryos. Transcriptomic analysis showed that vitrified-warmed blastocysts exhibited differentially expressed genes (DEGs) primarily associated with thermogenesis, chemical carcinogenesis-reactive oxygen species, oxidative phosphorylation, immune response, and MAPK-related signaling pathways. RT-qPCR confirmed increased expression of genes such as Cdk6 and Nfat2, and decreased expression of genes such as Dkk3 and Mapk10. Additionally, gene-microRNA interaction predictions and microRNA expression analysis identified twelve microRNAs with expression patterns consistent with the predicted results, suggesting potential roles in uterine epithelial cell adhesion, trophectoderm development, invasive capacity, and immune responses. Our findings suggest that vitrification induces transcriptomic changes in mouse blastocysts, and even small changes in gene expression can enhance implantation success. These results highlight the importance of understanding the molecular mechanisms underlying vitrification to optimize embryo transfer techniques and improve pregnancy outcomes.

Optimizing single blastocyst selection: the role of day 3 embryo morphology in vitrified-warmed blastocyst transfer cycles

Can day 3 embryo morphology serve as an independent criterion for optimal single blastocyst selection? This retrospective, single-centre cohort study included 1517 single vitrified-warmed blastocyst transfer (SVBT) cycles conducted between October 2019 and July 2022. The live birth rate (LBR) and other clinical outcomes of SVBT cycles were evaluated, considering both good-quality and non-good-quality day 3 embryos. The associations of day 3 morphological characteristics, encompassing number of blastomeres and embryo grade, were assessed. Multivariable analyses were undertaken using multiple models adjusted for day of blastocyst development and blastocyst grade. Blastocysts from good-quality day 3 embryos had significantly higher LBR compared with those from non-good-quality embryos for both day 5 (51.5% versus 42.9%; P = 0.013) and day 6 (25.1% versus 17.6%; P = 0.018) blastocysts. LBR did not differ significantly with number of blastomeres on day 3, regardless of day of blastocyst development (day 5/6) or blastocyst grade. LBR varied significantly by day 3 embryo grade for both day 5 (48.0%, 51.5%, 46.6% and 32.7% for grades I, II, III and IV-V; P = 0.005) and day 6 (41.5%, 23.6%, 15.9% and 16.1% for grades I, II, III and IV-V; P = 0.001) blastocysts. Multivariable logistic regression revealed that non-good-quality embryos and lower morphological grade (IV-V) on day 3 were significantly and negatively correlated with LBR, while the number of blastomeres on day 3 was not an independent factor. When selecting blastocysts of equal quality for SVBT cycles, those with higher day 3 morphological scores are preferred. Day 3 morphological evaluation is a valuable supplement to conventional selection methods.

Noneffectiveness of cryostorage duration on clinical and neonatal outcomes after single vitrified-warmed blastocyst transfers

BackgroundIn the current era of assisted reproductive technology, the strategy of single vitrified-warmed blastocyst transfer (SVBT) is acknowledged for positively impacting clinical outcomes and preventing the risk of multiple conceptions. Previous studies have indicated that blastocyst grade and the day of blastocyst positively correlate with outcomes. Moreover, storage duration has no significant effect on survival rates, clinical outcomes, and neonatal outcomes. However, some researchers express controversial opinions on cryostorage duration, and their findings suggest a negative impact on clinical outcomes. These results remain subject to controversy, and limited studies exist regarding the outcomes after SVBT. Therefore, our study aims to investigate the impact of the day of blastocyst, blastocyst grade, and blastocyst cryostorage duration on clinical and neonatal outcomes following SVBT in patients who underwent clomiphene-citrate-based minimal stimulation.Material and methodsIn this study, retrospective cohort study data collected from June 2015 to April 2023 included 2107 patients with first SVBT cycles who underwent a clomiphene-based minimal ovarian stimulation protocol or a drug-free natural protocol at the Ojinmed IVF Center. Patients were categorized into four groups based on blastocyst cryostorage duration: group 1 (< 2 months, n = 882), group 2 (3–6 months, n = 794), group 3 (7–12 months, n = 187), group 4 (13–24 months, n = 126), and group 5 (25–81 months, n = 118). The patient’s clinical and neonatal outcomes were compared with cryostorage duration after the propensity score matched.ResultMultivariable logistic regression analysis revealed that prolonged cryostorage duration insignificantly correlated with clinical outcomes. Additionally, neonatal outcomes are not correlated with cryostorage duration.ConclusionsThe patient must consider several parameters when selecting embryos for transfer, including the duration of cryostorage. Our study results show that for the first single vitrified-warmed blastocyst transfer of patients who underwent clomiphene citrate-based minimal stimulation, cryostorage duration does not affect outcomes.

P-240 Is the intelligent Data Analysis Score (iDAScore) a reliable tool to predict pregnancy? Our center’s experience

Abstract Study question Is the intelligent Data Analysis Score (iDAScore) reliable in predicting a positive pregnancy test, clinical pregnancy and miscarriage rate after single vitrified-warmed blastocyst transfer (SVBT)? Summary answer There is a significant increase in positive pregnancy test and clinical pregnancy rates as iDAScore increases. The miscarriage rate is lower with increased iDAScore. What is known already With the improvement of assisted reproductive technology (ART), elective single embryo transfer has become a standard. Optimizing embryo selection is a major challenge to increase reproductive outcomes. The Gardner embryo grading system is widely adopted for the evaluation of blastocyst quality, but this tool is subject to inter- and intra-variability. In recent years, artificial intelligence has found diverse applications in healthcare. Based on time-laps sequences of &amp;gt; 180’000 developing embryos, iDAScore is a new deep-learning model for objective and standardized blastocyst scoring. However, its reliability in predicting pregnancy and miscarriage rates remains unknown. Study design, size, duration This monocentric retrospective pilot study was conducted from May 2023 to December 2023. A total of 206 homologous SVBT cycles from 206 patients were analyzed (one patient, one cycle). Exclusion criteria included: cycles involving preimplantation genetic testing, multiple and/or fresh blastocyst transfer, and blastocysts obtained after testicular sperm extraction. All vitrified-warmed blastocysts were scored using iDAScore version 1.0 model, ranging from 1 – 9.9. Participants/materials, setting, methods Scores were stratified into 3 groups: high-score (9.9 – 7.7), medium-score (7.6 – 5.5) and low-score (5.4 – 3.1). For each group, positive pregnancy test, clinical pregnancy and miscarriage rates were analyzed. SVBT cycles were then stratified into four maternal age groups (&amp;lt; 35, 35-37, 38-40, &amp;gt;41 years) and the same outcomes were analyzed. χ2 was used for statistics analysis. Main results and the role of chance Mean maternal age was 36.8 ± 4.9. Among the 206 vitrified-warmed blastocysts, 122 were scored as high-score, 57 as medium-score and 27 as low-score. Positive pregnancy test rate was significantly higher with increased iDAScore with 58% in the high-score group, 36.8% in the medium-score group and 17% in the low-score group (p &amp;lt; 0.0001). Clinical pregnancy rate, defined as the visualization of a fetal heartbeat at ultrasound scan, was also significantly higher with increased iDAScore, with 51.6% in the high-score group, 31.6% in the medium-score group and 17% in the low-score group (p &amp;lt; 0.0001). The miscarriage rate was lower with increased iDAScore, with 8.1% in the high-score group, 16.6% in the medium-score group and 50% in the low-score group, but this difference was not statistically significative (p 0.032). When adjusted to age group however, the miscarriage rate was found to be significantly lower in the high-score group when compared to the medium-score group (p &amp;lt; 0.0001); statistical analysis was not achieved in the low-score group due to the small sample size. Limitations, reasons for caution The major limitation of our study is its small sample size. Data collection is ongoing, to increase the study power. Additionally, many other factors, such as genetic, hormonal, metabolic and/or immunological, may play a role in achieving pregnancy. Wider implications of the findings Our results indicate that iDAScore may be a strong predictor of pregnancy and could be used as a complementary tool to the Gardner embryo grading system in the decision-making process of which blastocyst to transfer. Trial registration number N/A

P-152 The impact of one-step fast warming protocol on vitrified-warmed blastocysts on reproductive outcome

Abstract Study question Does the implementation of one-step fast warming protocol affect the post warming quality of embryos and/or the reproductive outcome in frozen embryo replacement cycles? Summary answer The implementation of a one-step fast warming protocol provides similar survival, pregnancy, and clinical pregnancy rates with standard warming protocols. What is known already Cryopreservation process presents a significant challenge for embryos, as the formation of ice crystals can be lethal to their cells. Therefore, effective cryopreservation protocols are essential to mitigate this risk. Vitrification method protects the cells during cryopreservation by transforming water from a liquid state to a glass-like phase, thereby preventing the ice crystals formation. Moreover, the warming procedure can itself contribute to ice crystal formation, particularly through recrystallization. Studies have shown that embryo survival is related to warming rate and a one-step fasting warming protocol can be equally or more effective than the conventional protocol. Study design, size, duration This prospective randomized study was performed at Embryolab Fertility Clinic, in Thessaloniki, Greece between July and December 2023 and included 118 frozen embryo transfers. Both study and control group included only expanded blastocysts of good quality (AA or AB according to Gardner’s criteria). Control group was matched to the study group according to treatment, time period, woman age, quality of embryos and number of transferred embryos. The embryos were vitrified using open system. Participants/materials, setting, methods Fast warming group included embryos that were warmed using the one-step warming protocol: the embryos were exposed to 1M sucrose solution for 1’ at 37 °C and then immediately placed into culture media where laser-assisted hatching was performed. Control group included embryos that were warmed using conventional protocol: 1’ in 1M, 2’ in 0.5M, 2’ in 0.25M and 3’ in washing solution at room temperature and then placed into culture media for laser-assisted hatching. Main results and the role of chance The analyzed cases were 118 in total, 59 in the fast-warming group and 59 in the control group. Survival rate was 100% in both groups. Pregnancy rate (positive b-HCG) was not significantly different between the two groups: 72.41% in the fast-warming group and 67.79% in the control group (p = 0.687). Clinical pregnancy rate was also not significant between the two groups: 78.26% in the fast-warming group and 81.81% in the control group (p = 0.753). Limitations, reasons for caution The study included a limited number of cases, and information on the live birth rate was still pending. To establish the efficacy of fast warming conclusively, it is recommended that additional prospective randomized studies be conducted to validate its potential benefits. Wider implications of the findings One-step fast warming protocol resulted in similar survival rates post warm compared to the conventional warming protocol, while pregnancy and clinical pregnancy rates were not significantly different. Furthermore, it is worth noting that by minimizing the duration of the warming protocol, the workflow efficiency in the IVF laboratory is enhanced. Trial registration number N/A

P-116 Relationship between exposure in equilibration solution pre-vitrification for human collapsed blastocysts and miscarriage rate in ART treatments

Abstract Study question To explore the relationship between equilibration time pre-vitrification of human collapse blastocyst and clinical pregnancy and miscarriage rate in patients undergoing ART treatments Summary answer The miscarriage rate was significantly lower in the group with a short equilibration time of 7-8 minutes compared to the group of 9-10 minutes What is known already The introduction of vitrification represents one of the most important advancement in ART. However, protocols currently applied to cryopreserve human embryos still have some weak points that might be improved. A critical aspect is represented by the high concentration of cryoprotectants (CPAs) used during the vitrification and some of this CPAs might impact negatively cellular metabolism and function. Thus, this study investigated whether a shorter time in the equilibration solution before vitrification of artificially collapsed blastocysts might have an impact on survival and pregnancy outcomes, as well as live birth rate and risk of miscarriage in patients undergoing ART. Study design, size, duration This prospective study was performed at the Centre for Reproductive Medicine, Haikou Mary Hospital, China from March 2018 to May 2022. Informed consent for experimentation with human subjects was obtained before the patients start the ovarian stimulation. Female age &amp;lt;35 years, and causes of infertility included male factors, female infertility, and unexplained infertility. Following the fresh embryo transfer, supernumerary good quality blastocysts ≥ 2, according to Gardner’s score were vitrified and allocated as discussed below Participants/materials, setting, methods The study included a total of 831 expanded blastocysts, which were divided into two groups according to the equilibration time before vitrification: group (A) 7-8 minutes (413); and group (B) 9-10 minutes (418). Expanded blastocysts (grade 3 or more) were artificially shrunk by applying one or two laser pulses. Patients were included in the study only when at least two blastocysts were available for vitrification, in order to be allocated one in each group Main results and the role of chance Results: A total of 831 vitrified-warmed blastocysts were analysed in this study, of which 825 survived at the warming step (99.3%: 825/831). All surviving blastocysts were transferred in 585 embryo transfers. Overall, the clinical pregnancy rate per transfer was CPR: 68.5% (401/585), and live birth and miscarriage rates: 61.0% (357/585) and 11.0% (44/401). No significant differences were observed between the two groups regarding the mean age of patients, the average number of blastocysts transferred, the basal FSH, BMI, and infertility duration. Results show the same survival rate after warming for group A (99.3%) and group B (99.3%), as well as similar CPR (A: 69.1% versus B: 68.0%).The live birth (A: 63.8% versus B: 58.3%) and multiple gestation rates (A: 20.8% versus B: 23.5%) were comparable in the two groups. When analysing the overall miscarriage rate, data displayed a statistically significant difference (P &amp;lt; 0.05) in favour of group A (7.6%) compared to group B (14.2%). There were no differences between the two groups concerning the prevalence of male babies (A: 57.1% and B: 55.4%), average gestational length (A: 38.67±1.37 versus B: 38.33±1.21), preterm birth rate (A: 19.2% versus B: 20.6%), and birth weight (A: 2.95±0.58 versus B: 3.05±0.63 kg). Limitations, reasons for caution This is not a randomized controlled trial, it is a prospective observational cohort study aiming to calculate the effect of a shorted ES time on the risk of miscarriage. Also, potential confounding factors due to the heterogeneous nature of the sample investigated may impair the validity of our conclusions. Wider implications of the findings Results demonstrate that a shorter equilibration time resulted in optimal survival, clinical pregnancy, and live birth rates compared to exposure to ES for 9-10. Thus, suggesting that a longer exposure to the ES is not needed, and might negatively effect cellular metabolism and function, increasing the risk of miscarriage. Trial registration number Not applicatione

O-297 Prediction of pregnancy outcomes of single vitrified-warmed blastocyst transfer using combination of an automatic classification algorithm applied on cleavage stage embryos and blastocyst morphology

Abstract Study question Does combination of embryo assessment algorithm on cleavage-stage based on the automatic annotation of morphokinetic and blastocyst morphology in embryo selection improve implantation outcomes? Summary answer Combination of embryo assessment algorithm on cleavage-stage based on the automatic morphokinetic annotation and blastocyst morphological evaluation was showed significantly predictive for implantation outcomes. What is known already Conventional morphological assessment is still the gold standard for embryo selection. Timelapse monitoring of embryo development may represent a superior way to culture and select embryos in vitro. Nowadays, time-lapse culture systems are becoming more popular, many algorithms have been developed for embryo selection based on embryo morphokinetics, providing additional information for morphological assessment. However, manual annotations of developmental events and application of algorithms can be time-consuming and subjective processes. Automation of morphokinetic annotation can be a potential approach that reduces subjectivity in embryo selection. Study design, size, duration The observational, retrospective study was conducted in a single centre between 2020-2023 and included 511 single vitrified-warmed blastocyst transfer cycles. Blastocyst selected for transfer on Day 5,6 based on conventional morphological evaluation. Embryos were evaluated on Day 3 with a score from 1 (best) to 5 (worst) (from highest to lowest developmental potential) by the automatic embryo assessment algorithm. The correlation of the algorithms scoring and pregnancy outcomes was qualified by generalized estimating equations (GEEs). Participants/materials, setting, methods Embryos were cultured in timelapse GERI incubator and classified on day 3 by automatic embryo assessment algorithm depending on four parameters: P2 (t3-t2), P3 (t4-t3), oocyte age, and number of cells. The correlation of the algorithms scoring and pregnancy outcomes was qualified by generalized estimating equations (GEEs). Three GEE model using embryo assessment algorithm, conventional morphological assessment, and a combination of both classification system as the predictor were compared. Main results and the role of chance The implantation rate was higher with lower the scores generated by the embryo assessment algorithm. A GEE model showed the negative association between higher embryo score and lower odds of implantation. The OR of Score 3; 4; 5 vs 1 were 0.335; 0.259; 0.245 (95% CI 0.194-0.580; 0.138-0.485; 0.111-0.544, P = 0.000), respectively, for implantation. The AUC of the model using embryo assessment algorithm for implantation potential = 0.641. The AUC of the model combining both embryo assessment algorithm and conventional morphological assessment for implantation potential = 0.733. The differences were statistically significant (z-statistic = 3.896, p = 0.0001). Limitations, reasons for caution The sample size was enough to confirm the ability of the model for embryo selection. However, the retrospective nature of this study may be a limitation. Wider implications of the findings Using combination of timelapse technology with automated embryo assessment and conventional morphological assessment can predict the success rates of assisted reproduction cycles. To our knowledge, this is the first study using embryo dataset from single vitrified-warmed blastocyst transfer cycles with this embryo assessment algorithm. Trial registration number not applicable

P-128 Non-invasive morphometric assessment of embryo quality: Effectiveness of the number of trophectoderm cells at the equatorial region of expanded blastocysts

Abstract Study question Does the number of trophectoderm cells at the equatorial region of expanded blastocysts (eTEs) affects pregnancy rate in single vitrified blastocyst transfer (SVBT)? Summary answer The number of eTEs highly correlated with the total number of TEs. The greater number of eTEs was higher pregnancy rate became. What is known already The increased use of blastocyst transfer has emphasized the importance of selecting high-quality embryos. Morphological grading: Gardner’s criteria, or time-lapse imaging of embryo morpho kinetics is established a tool for selection of high-quality blastocysts. The Gardner’s criteria is one of the most used evaluation according to grading scores of developmental stage, trophectoderm (TE) and inner cell mass (ICM). Although, it cannot completely exclude subjectivity, and it varies from observer to observer. A quantitative evaluation method for blastocyst selection is necessary to solve these problems and to improve the pregnancy rate of SVBT. Study design, size, duration First, we checked the correlation between the number of eTEs and the total number of TEs using 23 discarded blastocysts by immunostaining of CDX2. Then, we analyzed 1103 vitrified-warmed blastocysts from July 2017 to June 2021 for pregnancy rates. Expanded blastocysts which reached the blastocoel cavity of 160 µm or more with obvious ICM were vitrified and cryopreserved. Relationship between the number of eTEs and pregnancy rate after SVBT was analyzed by logistic regression. Participants/materials, setting, methods CDX2-positive cells were defined as TE, and the difference between total cells by Hoechst staining and CDX2-positive cells as ICM. The correlation between the number of eTEs and the total number of TEs was examined. In SVBT, all embryos were monitored by a time-lapse system. eTEs were counted in the time-lapse image just before cryopreservation. Pregnancy and abortion rates were examined for each eTEs. Also, logistic regression analysis was performed on eTEs and pregnancy. Main results and the role of chance There was a strong positive correlation between the number of eTEs and the total number of TEs (CDX2-positive cells) in the whole blastocysts (r = 0.945). In addition, there was a significant correlation between the number of eTEs and the total cell number of blastocysts (r = 0.73). On the other hand, there was no correlation between the number of eTEs and the cell number of ICM (r = 0.008). The number of eTEs was presented as quartiles: Pregnancy rates for &amp;lt;5, 5-6, 6-7 and ≥7 eTEs were 25.9, 29.4, 38.4, and 64.2% (P &amp;lt; 0.05), respectively, and the miscarriage rates were 50.0, 28.3, 14.1 and 19.2% (P &amp;lt; 0.05), respectively. Pregnancy rate for ≥7 eTEs was significantly higher than that for the other groups (P &amp;lt; 0.05), and miscarriage rate was lower than that for &amp;lt;6 eTEs. That is, increased eTEs significantly increased the pregnancy rate and decreased the miscarriage rate. Significant relationship between the number of eTEs and pregnancy was shown by logistic regression analysis (P &amp;lt; 0.0001), with an AUC of 0.68 and a cutoff value of 6.5. Limitations, reasons for caution In this study, expanded blastocysts at 160 µm or more in diameter were analyzed and cryopreserved. The different size of blastocysts may be different number of eTEs, and the relationship between the number of eTEs and pregnancy rate will be needed to confirm in individual clinic. Wider implications of the findings Quantitative analysis of eTEs makes it possible to select highly fertile blastocysts. This assessment is simply and easy. It can be the additional possible evaluation before cryopreservation to allows for quantitative treatment of continuous variables by classifying them in more detail than Gardner’s criteria. Trial registration number N/A

P-229 Effect of morula pattern on clinical outcomes in single vitrified-warmed blastocyst transfer cycles

Abstract Study question Does morula pattern affect clinical outcomes in single vitrified-warmed blastocyst transfer cycles? Summary answer Ongoing pregnancy rate is statistically increased when transferring the blastocyst derived from fully compacted morula in single vitrified-warmed blastocyst transfer cycles. What is known already Time-lapse microscopy has enabled the detailed identification and measurement of dynamic events of embryo development. Recent studies have shown that the exclusion of one or more cells from the compacted morula is associated with reduced developmental competence and a decrease in pregnancy rate. Additionally, it is also associated with decreased rates of PGT-A euploid and implantation. These findings demonstrate the correlation between morula pattern and the outcomes of assisted reproductive technologies. Study design, size, duration A retrospective cohort study was performed between January 2020 and November 2023. A total of 99 single vitrified-warmed blastocyst transfer cycles (women ≥ 35 years) were analyzed. The rates of biochemical pregnancy, clinical pregnancy, implantation, miscarriage, and ongoing pregnancy were evaluated. Participants/materials, setting, methods Images of morula stage embryos were collected at 7-focal planes and every 5-minute interval using a time-lapse microscope. The morula stage embryos were divided into two groups according to their compaction patterns. Morula stage embryos without excluded or extruded cells were defined as fully compacted morula (FCM, n = 47). In contrast, Morula stage embryos with excluded or extruded cells were defined as partially compacted morula (PCM, n = 52). Main results and the role of chance There were no differences of patient characteristics between FCM and PCM regarding female age (37.8 ± 2.1 vs. 37.8 ± 1.8, p = 0.96), number of previous IVF failure (0.5 ± 1.1 vs. 0.9 ± 1.6, p = 0.23), number of retrieved oocytes (16.1 ± 4.0 vs. 14.3 ± 5.1, p = 0.14), maturation rate (86.5% vs. 89.1%, p = 0.18), fertilization rate (73.8% vs. 69.9%, p = 0.39), survival rate (100% vs. 100%, p = Not applicable), and number of transferred embryos (1.0 ± 0.0 vs. 1.0 ± 0.0, p = Not applicable), with the exception of rate of good-quality embryos on Day 3 (44.7% vs. 37.6%, p = 0.04). No statistical differences were observed in rates of biochemical pregnancy (44.7% vs. 34.6%, p = 0.31), clinical pregnancy (40.4% vs. 26.9%, p = 0.15), miscarriage (11.4% vs. 15.4, p = 0.57), and implantation (40.4% vs. 26.9%, p = 0.15) between FCM and PCM, respectively. However, FCM demonstrated a significantly increased ongoing pregnancy rate compared to PCM (29.8% vs. 11.5%, p = 0.02). Limitations, reasons for caution This study was conducted with a small sample size, which limited the generalizability of the findings. Therefore, further studies are needed with a larger sample size and more diverse populations to confirm our findings. Wider implications of the findings The compaction pattern of morula stage embryos can be an indicator for embryo selection. The blastocyst derived from fully compacted morula has the potential to improve ongoing pregnancy rate in single vitrified-warmed blastocyst transfer cycles. Trial registration number not applicable

P-134 Fatty acid supplementation during warming improves pregnancy outcomes after frozen blastocyst transfers: a propensity score-matched study

Abstract Study question Does warming with fatty acids (FAs) affect the viability of human blastocysts and pregnancy outcomes after a single vitrified-warmed blastocyst transfer (SVBT)? Summary answer FA-supplemented warming solutions promoted the blastocyst outgrowth by decreasing the degeneration of trophoblast cells and improved pregnancy outcomes after SVBTs. What is known already Vitrification is considered a well-established technique and has been used worldwide. However, previous studies demonstrated the detrimental effects of vitrification on pre-implantation development and term pregnancy in oocytes and embryos. Vitrification reduces the intracellular lipid content and decreases the competence for pre-implantation development. The FA supplementation into the warming solution restores the lipid content in the ooplasm and improves developmental competence by promoting the β-oxidation pathway in mice. Although, in humans, the FA-supplemented warming solutions reportedly improved pregnancy outcomes after vitrified-warmed cleavage-stage embryo transfers, the effectiveness of these solutions on blastocyst warming remain unclear. Study design, size, duration The experimental study included 401 discarded blastocysts. The blastocysts were warmed using the FA-supplemented (FA group) or non-supplemented (control group) solutions. The blastocyst adhesion, outgrowth area, and incidence of outgrowth degeneration were assessed. The retrospective cohort study included 4,426 treatment cycles from 4,426 women who underwent SVBTs between January 2023 and August 2023 (January–May 2023, control group; June–August 2023, FA group). Pregnancy outcomes were compared statistically between the groups. Participants/materials, setting, methods The implantation competence was experimentally examined using an outgrowth model. The blastocysts were placed on fibronectin-coated dishes and cultured for 96 hours. The embryos were designated as degenerated when the outgrowth area decreased by &amp;gt; 10%, compared with the maximum area. For the clinical study, multiple covariates that affected the outcomes were used for propensity score matching. The patients in the FA group were matched with controls using a propensity score in a 1:1 ratio. Main results and the role of chance The adhesion rate after the outgrowth culture was comparable between the control and FA groups. However, the outgrowth was larger in the FA group than in the control group. The multivariate linear regression analysis also demonstrated similar results. Furthermore, the incidence of outgrowth degeneration was significantly decreased in the FA group. Furthermore, the subgroup analyses revealed that FA-supplemented warming solutions were effective in blastocysts donated from young patients, day 5 blastocysts, and morphologically good blastocysts. For the retrospective cohort study, the implantation, clinical pregnancy, and ongoing pregnancy rates were significantly higher in the FA group than in the control group. The multivariate logistic regression analysis also demonstrated that warming with FA-supplemented solutions significantly increased the probability of ongoing pregnancies. However, the rates of early pregnancy loss and miscarriage in the first trimester were comparable between the groups. The subgroup analyses demonstrated a similar trend to in vitro experiments; the FA-supplemented solutions were more effective in good prognosis cases (young patients, day 4/5 blastocysts, and morphologically good blastocysts) than in poor prognosis cases (advanced age patients, day 6/7 blastocysts, and morphologically poor blastocysts). Limitations, reasons for caution This was a single-centre, retrospective study, necessitating further multicentre studies to ascertain the generalizability of these findings to other clinics with different protocols and/or patient demographics. Despite using propensity score matching and multivariate models to adjust for the confounders, we cannot adjust for all possible confounders. Wider implications of the findings FA-supplemented warming solutions improved pregnancy outcomes after SVBTs, particularly in patients with a good prognosis. These warming solutions could contribute to maximizing clinical outcomes, shortening treatment periods, and reducing patient burden. Trial registration number not applicable

P-244 Which embryo selection model should be prioritized for transfer of a single euploid blastocyst?

Abstract Study question Which embryo selection model would be given high priority for single euploid blastocyst transfer, iDAScore® v2.0, KIDScoreTM D5 v3.2 or conventional morphological grading system? Summary answer Prioritize morphological grading over embryo score for single euploid blastocyst transfers, and reverse the priority for single non-PGT-A blastocyst transfers. What is known already The use of effective tools, such as AI, morphokinetic data and the Gardner criteria, for embryo selection within in vitro fertilization (IVF) has the potential to increase the possibility of pregnancy. Nevertheless, previous studies indicated that the best embryo these tools prioritize may be inconsistent and controversial. Therefore, this study demonstrates integrated reference tables of FHB+ rates for selecting of single embryo transfer (SET) clinically, and assess the association between iDAScore®, KIDScoreTM, traditional morphological grading and embryonic ploidy status. Study design, size, duration Retrospective study from November 2022 to October 2023 with morphokinetic parameters of time-lapse monitoring analysis involving embryos from 264 patients who underwent day-5 single vitrified-warmed blastocyst transfer with or without preimplantation genetic testing for aneuploidies (PGT-A) (total SET=264; euploid=158; non-biopsied=106) using Embryocope® Plus incubators. After SET, the rates of FHB+ of each group were analyzed. Mean female age was 35.2 years. Participants/materials, setting, methods Blastocyst morphology was scored in 3 groups: good (AA, AB, BA), average (BB), poor-quality embryos (BC, CB, CC). Blastocysts were ranked established on the scores caused by iDAScore or KIDScore. All cycles were stratified into 4 score groups (8.1-9.9, 6.1-8.0, 3.7-6.0, 1.0-3.6). Assisted hatching was conducted on day 3. Trophectoderm biopsies were performed on day 5, and examine the embryonic ploidy status using a next-generation sequencing-based PGT-A platform (Thermo/Ion GeneStudio™ S5 Prime). Main results and the role of chance In D5 non-PGT-A SET group, the FHB+ rates of good-quality embryos were higher than those of average and poor-quality embryos (49% vs. 40% vs. 0%). According to the embryo score group, the group with higher scores showed better FHB+ rates (KIDScore: 56.9% vs. 47.2% vs. 16.7% vs. 0%; iDAScore: 59.1% vs. 49.6% vs. 14.9% vs. 0%). The non-PGT-A results indicated that embryo score should be given high priority. In D5 euploidy SET group, the FHB+ rates of good-quality embryos were higher than those of average-quality embryos (78.12% vs. 56.00% vs. 44.44%). According to the embryo score group, the group with higher scores did not show distinct better FHB+ rates (KIDScore: 65% vs. 69.51% vs. 47.6% vs. 0%; iDAScore: 64.1% vs. 67.7% vs. 38.8% vs. 0%). The PGT-A results indicated that morphological grading could be given high priority. Based on the data, we hypothesized that assisted hatching might lead to distortion in embryo scores. Limitations, reasons for caution The study is limited by its retrospective single center study with small sample size of single embryo transferred even some of the groups have no embryo transfer. Therefore, a prospective multicenter validation is necessary. Wider implications of the findings This study provides distinct tables for clinical embryo selection with or without PGT-A. Our findings support the potential application of the integration of AI, morphokinetic data and embryo quality prediction systems, and indicate the possibility of making appropriate decisions in different age groups clinically. Trial registration number Not Applicable

P-181 Chromosome constitution and clinical outcome of blastocysts derived from morulae with different compaction patterns

Abstract Study question Do blastocysts with a diverse history of compaction pattern (complete or partial) have different chances to be aneuploid and to implant? Summary answer Embryos undergoing partial or complete compaction have comparable chances to be aneuploid. Euploid blastocysts with previous history of blastomere extrusion have reduced chances of implantation. What is known already Compaction at the morula stage is an essential requisite for blastocyst formation and involves blastomere flattening and establishment of tenacious cell-to-cell contacts. Incomplete compaction is associated with several upstream and downstream morphokinetic anomalies. It also affects blastocyst yield and quality and clinical outcome. However, evidence on blastocyst chromosomal constitution and implantation potential after preimplantation genetic testing for aneuploidies (PGT-A) is lacking. Study design, size, duration This retrospective cohort study assessed laboratory and clinical outcomes of 1206 blastocysts derived from 483 infertile patients undergoing ART treatment and PGT-A from January 2015 to July 2022. Three age groups (≤34, 35–38 and ≥39 years) were adopted for sub-analyses. Biopsied blastocysts were vitrified and subsequently used in single vitrified-warmed blastocyst transfers (SVBT). Participants/materials, setting, methods Embryo development was monitored by time-lapse technology (TLT), also annotating abnormal cleavages and multinucleation. Patterns of morula compaction were assessed according to previously published categories: (i) full compaction, with all blastomeres undergoing compaction (FCM); partial compaction (partially compacted morula [PCM]), with (ii) blastomeres excluded from the outset (exc-PCM) or (iii) extruded after start of compaction (ext-PCM). Embryos were assessed in relation to embryonic and clinical outcomes. PGT-A data were obtained from trophectoderm biopsies. Main results and the role of chance Average maternal age of the overall patient population was 39.0 years. The full compaction pattern (FCM) was detected in 35.7% of all embryos. Partially compacted morulae showing excluded (Exc-PCM) or extruded (Ext-PCM) cells were also observed (54.4% and 9.9%, respectively) and collectively (64.3%) were the larger fraction (P &amp;lt; 0.0001, among all groups). Of 1206 analysed blastocysts, 551 were euploid, of which 366 were used in SVBT. Aneuploidy rate in the overall blastocyst population derived from FCM, Exc-PCM and Ext-PCM was 50.8%, 55.6%, and 60.0%, respectively (P &amp;gt; 0.05). However, in the younger maternal age group (≤34 years), the aneuploidy rate of the Exc-PCM group was higher compared with FCM (39.8% vs. 25.3%, P = 0.03). In the overall population, the Ext-PCM phenotype was associated with a lower implantation rate (FCM, Exc-PCM and Ext-PCM:47.8%, 44.7%, 55.6%, and 27,6%, respectively (P = 0.04), while miscarriage rates were comparable. Finally, transferred euploid blastocysts not classified according to maternal age implanted with comparable rates, irrespective of their morphokinetic history (abnormal division, multinucleation, no morphokinetic abnormalities). Limitations, reasons for caution The study is limited by its retrospective design. Having been obtained from a single centre, the data require independent validation Wider implications of the findings This study confirms and extends our previous findings on the implications of partial compaction. Importantly, it further consolidates the notion that the embryo can develop through atypical morphokinetic patterns while often preserving its genomic integrity and implantation ability. Trial registration number Not applicable

P-143 Comparison of clinical outcomes between overnight warmed and embryo transfer day warmed blastocysts in frozen embryo transfer cycles

Abstract Study question Is there any difference between clinical outcomes of overnight warmed (ONW) and embryo transfer day warmed (ETDW) blastocysts in frozen embryo transfer (FET) cycles? Summary answer ETDW blastocysts had better clinical outcomes compared to ONW blastocysts in FET cycles. What is known already Some studies reported that the resumption of mitosis in thawed cleavage-stage embryos resulted in significantly better clinical outcomes in FET cycles. Unnecessary transfer of non-functioning embryos can be avoided by incubating thawed embryos overnight to deselect embryos that developed abnormally or failed to undergo additional cleavage. The synchronisation between a viable embryo and a receptive endometrium is vital for successful implantation to take place. The optimal implantation rates occur with embryo-endometrial developmental asynchrony of ± 1.5 days or less. The implantation rates are progressively reduced when embryo-endometrial development asynchrony is greater than 3 days. Study design, size, duration This was a retrospective study involving 2368 FET cycles in KKIVF Centre, KK Women’s and Children’s Hospital, Singapore from Jan 2021 to Dec 2022. The transfer of embryos or blastocysts derived from thawed oocytes, cleavage-stage embryos, double blastocysts and cultured blastocysts from thawed cleavage-stage embryos were excluded. Only single vitrified-warmed blastocyst transfers (n = 1445) were included in this study. Participants/materials, setting, methods Cryopreserved blastocysts were routinely warmed one day before embryo transfer (ET) using Vit Kit - Warm (FUJIFILM Irvine Scientific®) and incubated overnight (ONW group). However, when ETs fell on Monday or post public holiday, vitrified blastocysts were warmed on ET day (ETDW group). Regardless of blastocyst age, surviving blastocysts were transferred into day 5 endometrium. Statistical analysis was performed using t-test or Chi-square test. Differences with P &amp;lt; 0.05 were considered as significant. Main results and the role of chance No statistical significant difference was observed in terms of maternal age distribution at the time of oocyte retrieval between ONW and ETDW groups (34.26 ± 3.29 vs. 34.49 ± 3.22, P = 0.221). Overall, clinical pregnancy rates (CPR) and live birth rates (LBR) were significantly higher in the ETDW group (CPR: 47.47% vs. 40.47%, P &amp;lt; 0.01; LBR: 34.99% vs. 28.78%, P &amp;lt; 0.05). Clinical outcomes were comparable in both ONW and ETDW groups for vitrified-warmed day 5 blastocyst transfers (CPR: 51.27% vs. 58.44%, P = 0.11; LBR: 37.06% vs. 44.81%, P = 0.07). CPR (45.02% vs. 25.71%, P &amp;lt; 0.0001) and LBR (32.03% vs. 17.45%, P &amp;lt; 0.0001) were significantly increased when vitrified day 6 blastocysts were warmed and transferred on the actual day of ET. 18.42% CPR and 13.16% LBR were achieved when vitrified-warmed day 7 blastocysts were transferred on the ET day itself. However, transfer of vitrified-warmed day 7 blastocysts in the ONW group did not result in any pregnancy. Limitations, reasons for caution Study subjects were not stratified according to patient’s age band and blastocyst quality. Age itself is an independent determinant of blastocyst quality which can affect clinical outcomes. Wider implications of the findings Warming of a vitrified blastocyst on ET day is preferred regardless of blastocyst age. However, to facilitate seamless operation in laboratory, overnight warming for vitrified day 5 blastocysts is feasible without compromising clinical outcomes. Trial registration number Not applicable

Comparable ongoing pregnancy and pregnancy loss rates in natural cycle and artificial cycle frozen embryo transfers with intensive method-specific luteal phase support; a retrospective cohort study

Study objectiveThe absence of corpus lutea in artificial cycle (AC) frozen embryo transfers (FET) may increase the chances of pregnancy loss. In this retrospective cohort study, the efficacy of AC endometrial preparation was compared natural cycle (NC) endometrial preparation in terms of ongoing pregnancy. MethodsOne thousand six hundred and eighteen consecutive vitrified-warmed blastocyst FET performed between December 2021 and November 2022 were included, with 1023 compared after exclusions according to the endometrial preparation method; 293 NC-FET, 143 modified NC-FET, 204 unprogrammed AC-FET, and 383 oral contraceptive pill (OCP) programmed AC-FET. Intensive method-specific luteal phase support (LPS) was administered in NC- (human chorionic gonadotropin and micronized vaginal progesterone), mNC- (micronized vaginal progesterone), and in AC-FET (micronized vaginal progesterone, intramuscular progesterone, and oral dydrogesterone). ResultsClinician choice of endometrial preparation method resulted in the NC- or AC-FET groups having distinct differences, with female age, antral follicle count and body mass index as well as the percentage of DOR or PCOS diagnosed patients significantly different. The unadjusted ongoing pregnancy and total pregnancy loss rates for NC-, mNC-, AC-, and ocp-AC-FET were 61.8 %, 55.2 %, 57.4 %, and 58.5 %, and 19.2 %, 24.0 %, 23.5 % and 23.8 %, respectively. In multivariate logistic regressions to predict the dependent outcomes of ongoing pregnancy and total pregnancy loss, none of the FET methods were selected as independent predictors. ConclusionPatients undergoing NC- and AC-FET with method-specific progesterone LPS had comparable ongoing pregnancy rates as well as total pregnancy loss rates, with NC-FET ranked first in the regression analysis.

Obstetrical and neonatal outcomesafter vitrified-warmed blastocyst transfer in day 1 rescue intracytoplasmic sperm injection cycles: a retrospective cohort study.

Fertilization failure often occurs in conventional IVF cycles, and day 1 rescue ICSI is frequently recommended. In this study, the effect of rescue ICSI on obstetrical and neonatal outcomes after a single blastocyst transfer in vitrified-warmed cyclesis evaluated. This cohort study was a retrospective analysis of 703 vitrified-warmed single blastocyst transfers and 219 singletons in the r-ICSI group compared with 11,611 vitrified-warmed single blastocyst transfers in the IVF/ICSI and 4472 singletons in the IVF/ICSI group, respectively, and patients just undergoing their first IVF treatments were included in this study. Pregnancy rate (PR), live birth rate (LBR), and singleton birthweight were the primary outcome measures. Multiple linear regression analysis and logistic regression analysis were performed to evaluate the possible relationship between obstetrical and neonatal outcomes and fertilization method (including IVF, ICSI, and r-ICSI) after adjusting for other potential confounding factors. PR and the LBR were lower in the r-ICSI group compared with the IVF/ ICSI group. Singletons from the r-ICSI group had a higher Z-score and the proportion of large for gestational age (LGA) newborns was greater compared with singletons from the IVF/ICSI group. The results of the study indicated that a 31% LBR after r-ICSI is acceptable for vitrified-warmed blastocyst transfer, but the safety of transfer is a concern because of the lower PR and LBR compared with IVF/ICSI. The safety of r-ICSI newborns is also a concern because of the significantly higher birthweight and the proportion of LGA in r-ICSI group newborns compared with the IVF/ICSI group.

Impact of inclusion of a poor-quality embryo with a good-quality embryo on pregnancy outcomes in vitrified-warmed blastocyst transfers

Research questionDoes the co-transfer of a good-quality embryo and a poor-quality embryo influence pregnancy outcomes in comparison to the transfer of a single good-quality embryo in vitrified-warmed blastocyst transfer cycles? DesignThis retrospective cohort study involved a total of 11,738 women who underwent IVF/intracytoplasmic sperm injection cycles and vitrified-warmed blastocyst transfer at a tertiary-care academic medical from January 2015 to June 2022. The study population was categorized into two groups: single-blastocyst transfer (SBT; participants who underwent single good-quality embryo transfer, n = 9338) versus double-blastocyst transfer (DBT; participants who underwent transfers with a poor and a good-quality embryo, n = 2400). ResultsThe live birth rate (LBR) was significantly higher in the DBT group in comparison with the SBT group (65.6% versus 56.3%, P < 0.001). Multivariable logistic regression analysis showed that DBT was an independent predictor for LBR with a strong potential impact (adjusted odds ratio 1.55, 95% confidence interval 1.41–1.71; P < 0.001). However, the multiple birth rate was significantly higher in the good-quality embryo and poor-quality embryo group compared with patients undergoing a single good-quality embryo transfer (41.4% versus 1.8%; P < 0.001). ConclusionsIn vitrified-warmed blastocyst transfer cycles, LBR was higher following DBT with one good-quality and one poor-quality embryo compared with SBT. However, this was at the expense of a marked increase in the likelihood of multiple gestations. Physicians should still balance the benefits and risks of double-embryo transfer.