Single Blastocyst Transfer Cycles Research Articles

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-153 Optimizing clinical outcomes in single vitrified-thawed blastocyst transfer cycles: impact of blastocyst re-expansion status

Abstract Study question is the blastocyst re-expansion status according to the thawing-transfer time interval related to the clinical outcomes in a single frozen-thawed blastocyst transfer cycles? Summary answer The post-thawing blastocyst shrinkage is linked to lower clinical outcomes, and minimizing the time between thawing and transfer optimizes outcomes especially for shrunken blastocysts. What is known already • A reduced ART outcome was observed with the use of shrunken post-warming blastocysts (Ito et al., 2023) • The spontaneous blastocyst shrinkage observed during in vitro embryonic development is considered as a negative prognosis factor for implantation (Sciorio et al., 2020) • The blastocyst’s re-expansion level after thawing proves to be the best post-thaw parameter for the prediction of live birth (The Vienna consensus., 2017. Ahlstrom et al., 2013). • The fast blastocele re-expansion seems to have a predictive value for implantation in frozen-thawed blastocyst transfer cycle (Shu et al., 2009). Study design, size, duration This was a retrospective study of 577 single frozen-thawed blastocyst transfer cycles from January 2022 to April 2023. Participants/materials, setting, methods Only B4 and B5 blastocyst quality obtained in day-5 were included in this study. The morphological characteristics were evaluated: after thawing (T0) and at Transfer time (TR). Blastocysts with 50% reduction of blastocele were classified “Shrunken”, the rest are “re-expanded”. and categorized into Group-1: re-expanded at T0 (n = 173); Group-2: shrunken at T0 and re-expanded at TR (n = 135); Group-3: shrunken at T0 and TR (n = 199). Statistical tests: chi-square, T-test and Mann-Whitney. (Statistical significance p < 0.05*). Main results and the role of chance Clinical outcomes of re-expanded blastocysts comparing to shrunken blastocysts at TR were respectively 42.21% versus 32.71% for pregnancy rate (PR) (p < 0.007),39.61% versus 30.48% for implantation rate (IR) (p < 0.02) and 35.71% versus 22.30% for life birth rate (LBR) (p < 0.004), a significantly higher outcomes were observed for re-expanded blastocysts. The miscarriage rate decreased from 25.00% to 9.23% (p < 0.001). The transfer of shrunken blastocysts in an interval of time within 1 hour or less comparing to more than 1 hour between T0 and TR showed the following results: PR = 40.82% versus 28.07% (p < 0.032), IR = 39.81% to 25.10%, (p < 0.02) and LBR = 26.53% versus 19.88% (p < 0.2). a significantly higher clinical outcomes were observed for shrunken blastocysts transferred within 1 hour or less. Group analysis: the PR, IR and LBR significantly increased for Group-1 comparing to Group 2. For Group-3, shrunken blastocysts at TR had the lower outcomes. (respectively p = 0.003; 0.017; 0.0002) Limitations, reasons for caution It is an ongoing retrospective observational study. Blastocysts with a low quality (B3 or less) were excluded from this study how limit our ability to extend the findings to low morphology degrees not covered by this research. Wider implications of the findings The management of frozen blastocyst transfers in IVF laboratories have to take into consideration in addition to the classic morphological evaluation, the blastocoele re-expansion state and the time interval between thawing and transfer to optimize the transfer outcomes. Trial registration number not applicable

P-588 Serum Luteinizing Hormone levels before progesterone supplementation are significantly associated with live birth rate in single euploid frozen embryo transfers performed in hormonal replacement cycles

Abstract Study question Do luteinizing hormone (LH) levels measured prior to initiating progesterone supplementation influence live birth rate (LBR) in artificial frozen-thawed single euploid blastocyst transfer cycles? Summary answer Serum LH levels, measured prior to progesterone initiation in artificial frozen-thawed single euploid blastocyst transfer cycles, are significantly associated with LBR. What is known already In the absence of a dominant follicle, estrogen supplementation in artificial endometrial preparation for frozen embryo transfer (FRET) can lead to a rise in endogenous LH levels, as observed in a natural cycle. Since the LH rise is a key feature in natural conception and the embryo, the endometrium, and the myometrium display receptors for LH, the rise observed during FRET preparation may have an impact on the clinical outcomes of the treatment. Previous studies found contradictory results hence none of them excluded embryo aneuploidy by implementation of preimplantation genetic testing for aneuploidies and the transfer of euploid embryos. Study design, size, duration Retrospective analysis of 639 frozen-thawed single euploid blastocyst transfer cycles performed in a tertiary referral IVF center from January 2018 to August 2023. Cycles with hormonal pre-treatment or pituitary suppression were excluded. Participants/materials, setting, methods Single euploid FRET cycles were included. Oral estradiol administration commenced on cycle-day 2/3. Estradiol, progesterone, and LH were measured at the start of endometrial preparation and up to 3 days before progesterone initiation, and the slope of LH was calculated. Patients were stratified in groups according to their LH values before progesterone administration, and the impact of LH on LBR and implantation rate was assessed. Logistic regression analysis was performed to adjust for potential confounders. Main results and the role of chance In total 639 cycles were included. Patients’ characteristics (mean+/-SD) were: age 33.2±5.9 years; BMI 27.5±4.9 kg/m2. The median duration of estrogen administration was 15 days (range: 11-27 days). The overall implantation rate and LBR were 65.9% (421/639) and 46.9% (300/639), respectively. Patients were stratified into six groups according to their LH levels prior to progesterone supplementation: <10th percentile (≤6mIU/ml, n = 57), p10th-p25th (>6 to ≤ 8.5mIU/ml, n = 81), p25th-p50th (>8.5 to ≤ 12.4mIU/ml, n = 176), p50th-p75th (>12.4 to ≤ 18.1mIU/ml, n = 180), p75th-p90th (>18.1 to ≤ 25.0mIU/ml, n = 91) and >p90th (>25.0mIU/ml, n = 54). A significant trend for higher LBR with increasing serum LH levels was observed (Cochran-Armitage Test, P = 0.041) but not for implantation rate (P = 0.158). Those with higher basal serum estradiol levels before estrogen supplementation had a steeper LH increase from basal to progesterone-supplementation day (0.40 mIU/mL higher per 10pmol/L increase in basal estradiol, P = 0.027). Regression analysis identified as independent predictors of LBR BMI (OR 0.96, 95%CI: 0.93-0.99) and embryo quality (CC vs. AA p < 0.001, CB vs. AA p = 0.027, BC vs. AA p = 0.013). Patients with steeper LH increases from estrogen to progesterone-supplementation day had higher LBR in both univariable (OR:1.27, 95%CI: 1.00–1.63, P = 0.052) and multivariable analyses (OR:1.26, 95%CI: 0.97–1.64, P = 0.085) but the difference didn’t reach statistical significance. Limitations, reasons for caution The retrospective design of the study is a limitation. Results should be interpreted with caution due to the small number of patients in the lowest and highest LH percentile groups. Wider implications of the findings The results of this study suggest that serum LH levels measured before progesterone supplementation may have an impact on the clinical outcome of artificial frozen-thawed blastocyst transfer cycles. Further studies with a higher sample size are necessary to confirm or refute our findings. Trial registration number not applicable

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-213 Effectiveness and safety of single poor quality blastocyst transfer compared with single good quality blastocyst transfer in the first transfer cycle

Abstract Study question Comparison of pregnancy and perinatal outcomes in blastocysts with poor inner cell mass quality or poor trophectoderm quality to optimize non-quality single blastocyst transfer strategies. Summary answer Poor trophoblast quality blastocysts have better pregnancy outcomes than poor inner cell mass quality blastocysts, with no statistically significant difference in perinatal outcomes What is known already There is no doubt that good-quality blastocysts have better pregnancy outcomes than poor-quality blastocysts, but the preference for trophectodermal poor-quality blastocysts or inner cell mass poor-quality blastocysts in non-good-quality blastocyst cycles is still uncertain. Study design, size, duration A total of 46,433 first single blastocyst transfer cycles from March 1, 2014, to December 31, 2022 were retrospectively analyzed, and blastocyst transfer cycles were divided into 3 groups according to the grade of trophoderm and inner cell mass: A/B A/B (Group 0, N = 30748), A/B C (Group 1, N = 15455), and C A/B (Group 2, N = 230). Participants/materials, setting, methods 46,433 patients who underwent their first single blastocyst transfer at Reproductive and Genetic Hospital of CITIC-Xiangya were included. Multivariate log-binomial regression model with COPY methods were performed to estimate relative risk of Group 2/1 versus Group 0 and Group 2 versus Group 1 for reproductive and neonatal outcomes. Five propensity score weighting methods, namely IPW, processing, overlap, matching, and entropy, were used for sensitivity analysis to explore the robustness of the results. Main results and the role of chance After adjusting for female age, BMI, duration of infertility, number of cycles, AFC, AMH, endometrial thickness, causes of infertility (tubal disorders, ovulatory disorders, endometriosis, unexplained, more than one causes, male factors), culture days (D5, D6), expansion of blastocyst (3, 4, 5, 6), and type of blastocyst (fresh blastocyst, thawed blastocyst, thawed cleavage cultured to blastocyst, PGT blastocyst), we found that clinical pregnancy rate (CPR) and live birth rate (LBR) of Group 0, Group 1 and Group 2 were successively significantly decreased (CPR: Group 1 vs Group 0, RR = 0.83 (0.81, 0.84), Group 2 vs Group 0, RR = 0.43 (0.35, 0.53), Group 2 vs Group 1, RR = 0.53 (0.42, 0.64); LBR: Group 1 vs Group 0, RR = 0.79 (0.77, 0.81), Group 2 vs Group 0, RR = 0.36 (0.27, 0.47), Group 2 vs Group 1, RR = 0.45 (0.34, 0.59); respectively), while early miscarriage rate was successively significantly increased (Group 1 vs Group 0, RR = 1.3 (1.22, 1.38), Group 2 vs Group 0, RR = 2.25 (1.46, 3.15), Group 2 vs Group 1, RR = 1.73 (1.12, 2.42)). Late miscarriage, preterm birth, singleton live birth, sex ratio of singleton, low birth-weight of singleton, and birth weight of singleton were not statistically different between three groups. Above results were robust in our two sensitivity analysis. Limitations, reasons for caution As a retrospective study, there are inevitably unmeasured confounding factors. This study only included a small number of Group 2. It’s therefore possible that our study was under powered. Risk of gestational hypertension, gestational diabetes, cesarean section and macrosomia should also be evaluated with a more comprehensive assessment of safety. Wider implications of the findings High-quality blastocysts have better pregnancy and live birth rates than poor-quality blastocysts, but there are no significant differences in preterm birth, sex ratio, or birth weight. In the absence of good quality blastocysts for transplantation, poor quality blastocysts of the trophectoderm are preferred over poor quality inner cell mass. Trial registration number not applicable

P-170 Clinical evaluation of an image-based artificial intelligence model for embryo selection: a double-blinded randomized comparative reader study

Abstract Study question What is the performance of an image-based artificial intelligence (AI) model for ranking blastocyst stage embryos compared to embryologists using traditional morphology? Summary answer The AI was non-inferior to manual embryo selection. The AI showed significant improvement in clinical pregnancy when there was disagreement between AI and manual selection. What is known already In previous work, we developed an image-based AI model that predicts the likelihood of clinical pregnancy by analyzing a single static image of a blastocyst captured prior to biopsy or freeze. This model was trained on data from over 8,000 single-blastocyst transfer cycles from multiple U.S. IVF clinics performed between 2014 to 2021. Study design, size, duration We performed a retrospective, double-blinded, comparative reader study. The study included data from 438 single-blastocyst transfers from 10 different IVF clinics in U.S. that were not part of previous model development or testing. Using this data, a set of 1,257 virtual patient panels were created. Each virtual patient panel included between 2-5 embryos that were matched by age (18 - 29, 30 - 34, 35 - 37, ≥38), race (white, non-white, and unknown) and PGT-status. Participants/materials, setting, methods A group of 5 embryologists (readers) with varying levels of experience were asked to select their top embryo for transfer for each virtual patient panel (control arm) based on morphology grades. The AI model was also used to select a top embryo for transfer from each patient panel (treatment arm). The clinical pregnancy rates of the top-selected embryos were calculated and compared. Main results and the role of chance There was disagreement on the top pick embryo amongst the five embryologists 34.6% of the time, which increased to 43.9% when there were 3 or more embryos to choose from, supporting the need for a tool to standardize this decision. The clinical pregnancy rate of the control arm (average of embryologist readers) was 61.0% (individual rates of 58.9%, 59.6%, 61.5%, 61.6%, and 63.3%), and the clinical pregnancy rate of the treatment arm (AI model) was 62.3% (demonstrating non-inferiority with p<.001). The pregnancy rate of random embryo selection was 53.2%. All 5 of the embryologist readers agreed on the top-pick embryo 65% of the time. When all 5 readers agreed, the AI model disagreed with that consensus 31% of the time, and in these cases the AI model pregnancy rate was significantly higher by 8.6% (AI: 63.1%, Embryologist Consensus: 54.5% (p < 0.05)). Limitations, reasons for caution While data for this study was collected prospectively, the analysis was done retrospectively. Furthermore, readers were provided morphology grades from retrospective data rather than grading the embryos themselves. However, it is common for an embryologist to make an embryo selection based on morphology grades previously assigned by a different embryologist. Wider implications of the findings The AI model was able to select the top embryo for transfer with performance comparable to experienced embryologists. Such a model could allow for automated and objective embryo selection using a single static image of blastocyst stage embryos. Trial registration number NA

P-672 Is there a sweet spot for follicular size and/or estradiol level for the initiation of micronized progesterone to optimize natural proliferative phase (NPP) cryo-cycle outcome?

Abstract Study question Is there an optimal follicular size and/or estradiol level for the initiation of micronized progesterone to optimize outcomes in NPP cycles potentially restricting scheduling flexibility? Summary answer All follicular sizes >12 mm and estradiol levels >120 pg./mL do not significantly correlate with ongoing pregnancy rates (OPR) or pregnancy loss (PL). What is known already Planning of a frozen embryo transfer (FET) is feasible within either a natural (NC) or artificial cycle (AC). While AC-FETs offer flexibility in planning, concerns have raised due to studies indicating a higher risk for obstetric complications. Conversely, NC-FETs show a protective effect against these complications but are usually less flexible in planning and ask for more monitoring. Recently, the natural proliferative phase (NPP) protocol was described, in which luteal phase support is initiated as soon as the endometrium reaches 7mm. NPP-FETs were associated with ongoing pregnancy rates comparable to AC- and NC-FETs. Study design, size, duration A retrospective single-centre study including a total of 300 consecutive single frozen embryo transfers (FET), performed at a tertiary fertility centre between March 2023 and December 2023. All cycles were single blastocyst transfer cycles retained from IVF/ICSI cycles with autologous oocytes. Participants/materials, setting, methods A total of 227 patients underwent one or more frozen embryo transfer cycles. Administration of MVP 800mg BID was initiated after fulfilling the following criteria: follicular size > 12mm, estradiol level ≥120ng/mL and endometrium thickness ≥7mm. Blastocyst transfers were scheduled on the fifth day of MVP administration. Serum progesterone (P4) levels were determined on the day of transfer. Associations between treatment outcome, patient and cycle characteristics were explored using generalized estimating equations analyses. Main results and the role of chance The follicular size and estradiol level on the day of MVP initiation was not significantly associated with pregnancy rate (PR), ongoing pregnancy rate (OPR) or pregnancy loss (PL) (p = 0.386 and p = 0.260; p = 0.830 and p = 0.467; p = 0.978 and p = 0.313 respectively). Mean number of visits needed prior to the initiation of the MVP for scheduling the embryo transfer was 2.4 (SD 1.3). PR, but not OPR, was significantly associated with both the duration of the follicular phase as well as the number of visits (p = 0.008 and p = 0.006 respectively). For 91.3 % (274/300) of patients, embryo transfer could be scheduled on a weekday. 49% (146/300) of patients had a positive hCG test after the fresh blastocyst transfer in the NPP cycle. Ongoing pregnancy rate was 35 % (104/300), whereas pregnancy loss (early clinical miscarriage and biochemical pregnancy) was 23% (33/146). The OPR was significantly related to the age of the patient (p = 0.029). Both the PR as the OPR were significantly related the blastocyst quality (p = 0.008 and 0.009 respectively). The incidence of pregnancy loss was only significantly associated with blastocyst quality (p = 0.027). Mean serum P4 level at day of transfer was 19.4 ng/ml (SD 6.1) with a P4 level above 10ng/ml in 97% of cycles. Limitations, reasons for caution The retrospective character is a limitation of this study as well as the absence of live birth rate as a clinical outcome variable. Wider implications of the findings Flexibility about the required follicular sizes and estradiol levels open the perspective for exploring more flexible planning criteria such as lower thresholds for endometrial thickness. Further studies are needed to investigate whether ovulation occurs with formation of functional corpora lutea to effectively protect against hypertensive disorders. Trial registration number ONZ-2024-0015

P-429 Measuring serum progesterone levels on the day of a fresh blastocyst transfer is debatable as there is no evidence for correlation with ongoing pregnancy results

Abstract Study question Does serum progesterone (P4) level on the day of a fresh blastocyst transfer relate to ongoing pregnancy rate (OPR)? Summary answer OPR after a fresh single blastocyst transfer seems not to be associated with serum P4 level on the day of transfer. What is known already Several studies have suggested an optimal serum P4 threshold for embryo transfers in frozen embryo transfer cycles. However, for fresh embryo transfers, data are scarce and conflicting. Study design, size, duration A retrospective single-center cohort study was performed on 598 complete data cycles, retained out of 631 consecutive fresh single blastocyst transfer cycles. Data were collected from patients undergoing a fresh IVF/ICSI cycle with autologous oocytes at a tertiary fertility center between June 2022 and August 2023. Participants/materials, setting, methods A total of 482 unique patients underwent one or more single fresh blastocyst transfers using micronized vaginal progesterone (MVP) 800mg BID for luteal phase support starting day after oocyte retrieval. Serum P4 levels were determined on day of transfer. The primary endpoint was OPR, positive hCG-test and early pregnancy loss (EPL) were secondary endpoints. Unadjusted and adjusted generalized estimating equations (GEE) assessed P4 level association with the endpoints, using an exchangeable working correlation matrix. Main results and the role of chance No association was identified between P4 levels on day of transfer and OPR after accounting for maternal age, blastocyst quality, P4 and estradiol level at last ultrasound, BMI and endometrial thickness. Data were grouped according to 10/50/90 and 25/50/75 percentiles, resulting in groups < = or > 27ng/ml and < = or > 40ng/ml, with omission of 90th and 75th percentile groups due to right-skewed distribution. With serum P4 levels higher than 40ng/ml, the probability of a positive hCG-test significantly increased (OR 1.79, CI 1.11-2.91; p = 0.018). No significant difference was observed in patients with serum P4 < = or > 27ng/ml (OR 1.23, CI 0.66-2.30; p = 0.506). Regarding OPR, no significant differences were observed when comparing patients with serum P4 < = or > 27/ng/ml or < = or > 40ng/ml (OR 0.88, CI 0.42-18.85; p = 0.736 and OR 1.41, CI 0.83-2.37; p = 0.203, respectively). Moreover, EPL did not significantly differ between serum P4 level groups (OR 1.93, CI 0.61-6.13; p = 0.265 and OR 1.2, CI 0.51-2.84; p = 0.674). Age (p < 0.001) and embryo quality (p < 0.001) are significantly related with OPR. Additionally, late follicular progesterone levels and OPR are significantly associated (OR 2.39, CI 1.16-4.95 in patients with P4 < = or > 27/ng/ml and OR 2.21, CI 1.07-4.55 in patients with < =40ng/ml and >40ng/ml). Limitations, reasons for caution Limitations include the retrospective design and the lack of live birth outcome data. Progesterone levels exceeding 60 ng/ml were not further analyzed to their precise value but grouped as 60 plus which did not allow to identify potential detrimental effects of very high P4 levels on treatment outcome. Wider implications of the findings Our data suggest that measuring P4 on the day of a single blastocyst transfer with MVP luteal phase support may not be indicative of OPR or the risk of EPL. This raises questions regarding the necessity for routine P4 measurements as well as the development of rescue strategies. Trial registration number ONZ-2023-0628

P-435 Superiority of modified natural cycle vs hormonal replacement therapy in non-menopausal egg recipients of advanced maternal age: clinical outcomes from 1273 single blastocyst transfer cycles

Abstract Study question Is the modified natural cycle (mNC) better than hormonal replacement therapy (HRT) for endometrial preparation in non-menopausal egg recipients of advanced maternal age? Summary answer In women above 40 years, mNC shows better reproductive and obstetrical outcomes compared to hormonal replacement therapy, especially in the subgroup 45-50 years old. What is known already There is extensive evidence showing the superiority of mNC over HRT in terms of live birth rates, miscarriages, and even obstetric complications. Apparently, the presence of the corpus luteum plays a major role in endometrial receptivity and embryo implantation, probably allowing for better placentation. Nevertheless, there is a general belief that the ovulatory cycle of older women is not the best choice for endometrial preparation, although paradoxically they are the group of patients who could benefit most from the reduction of obstetric complications. An increase in cancellation rates for mNC is claimed, without consistent data available. Study design, size, duration Retrospective single-centre comparative clinical study, including 1273 endometrial preparation cycles for frozen single-blastocyst transfer between January 2020 and December 2022: 892 (70,2%) on HRT protocol and 381 (29,8%) on mNC protocol. The two groups were homogeneous for donor’s age (25,7 years HRT vs 25,3 years mNC), recipient’s age (42,2 years HRT vs 42,1 years mNC), severe male factor (6% HRT vs 5% mNC), and the need for a sperm donor (28% HRT vs 26% mNC). Participants/materials, setting, methods Among 1273 started non-menopausal recipient’s cycles, we compared cancellation rates between HRT and mNC due to either medical reasons (inadequate endometrium, bleeding, premature ovulation) or other issues (no embryo survival, COVID-19, etc). We studied the outcomes of the 1096 elective frozen single-blastocyst transfers performed, comparing HRT and mNC cycles for: pregnancy, clinical pregnancy, miscarriage, live birth and <35weeks preterm birth rates. We stratified the results by age and used Chi-square test to compare groups (p < 0,05). Main results and the role of chance The overall cancellation rate was 13.9%. No significant differences in cancellation for medical reasons were found between HRT (7%) and mNC (6.8%), p = 0.93. When we analyse results stratified by age, patients aged 39 or less (270 cycles: HRT 75.9%, mNC 24.1%) showed no statistically significant differences in pregnancy (58% vs 64.6%, p = 0.35), clinical pregnancy (50.7% vs 56.9%, p = 0.34), miscarriage (18.3% vs 18.9%, p = 0.93), and live birth rates (41.5% vs 46.2%, p = 0.5). In the 40-44 age group (494 cycles: HRT 64.2%, mNC 35.8%), no statistically significant differences were found between HRT and mNC in pregnancy (58.2% vs 61.5%, p = 0.47), clinical pregnancy (50.8% vs 51.1%, p = 0.96), and live birth rates (40.4% vs 45.8%, p = 0.25). The HRT group had a significantly higher miscarriage rate (21%) compared to mNC (10%), p = 0.03. For patients aged 45-50 years (332 cycles: HRT 72%, mNC 28%), no statistically significant differences were observed in pregnancy (56.5% vs 62.4%, p = 0.33) and miscarriage rates (24.3% vs 15.1%, p = 0.18). Clinical pregnancy (44.8% Vs 57%, p = 0.04) and live birth rates (33.9% vs 48.4%, p = 0.01) were significantly higher in the mNC group compared to HRT. No significant differences were found between HRT and mNC in preterm birth rates <35 weeks (3.6% vs 4.6%, p = 0.75). Limitations, reasons for caution This study is a single-centre retrospective comparative trial. Our homogeneity study included several confounding variables, however other bias such as severe uterine factor, embryo quality or repeated implantation failure cases were not taken into account. Wider implications of the findings Modified natural cycle should be encouraged as the first option for endometrial preparation in non-menopausal egg recipients of advanced maternal age, having shown superiority over hormonal replacement therapy in patients aged 45-50 years. Moreover, modified natural cycles are more patient friendly and cost-effective, with no increase in the cancellation rates. Trial registration number not applicable

O-130 The spatial conformational features of blastocysts can serve as a new basis for selection

Abstract Study question Can spatial conformational features become a new basis for blastocyst selection? Summary answer The spatial conformational features of blastocysts can be associated with clinical outcomes, which is a new basis for blastocyst selection. What is known already At present, the quality evaluation of blastocysts is two-dimensional, and there are relatively few evaluation indicators. There are now methods for exploring three-dimensional reconstruction of blastocysts, including fluorescence staining to obtain three-dimensional structures or artificial rotation to obtain images and restore three-dimensional conformations. However, one drawback of these methods is that they are far from true clinical applications. There are no reports on the reconstruction techniques that can be used in clinical blastocyst selection techniques, and there are no reports on the spatial conformational features related to them. Study design, size, duration This study included 2,141 frozen thaw single blastocyst transfer cycles at Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology from 2020 to 2021. Simultaneously collect multi-focal plane (11) image data for each blastocyst (EmbryoScope+). The inclusion criteria for patients are those under 40 years old, with an endometrial thickness of 7-16mm, and a history of embryo transfer failure of less than or equal to 1 time. Participants/materials, setting, methods This study iteratively interpolated the 11 focal planes using a multi focal plane generation network model. The contour and spatial information of blastocyst TE and ICM were obtained through deep-learning and segmentation networks. Texture information was extracted using depth estimation and image fusion and mapped to a 3D model to obtain a complete blastocyst spatial model. Then calculate a series of new spatial conformational features of the blastocyst and analyze their correlation with clinical outcomes. Main results and the role of chance We validated the model using the fluorescence reconstruction of human blastocysts as the gold standard (key indicator accuracy>90%). The obtained spatial conformational parameters of blastocysts include: Blastocyst: overall volume (BOV), cystic cavity volume (BCV), surface area (BSA); ICM: volume (IV), surface area (ISA), spatial aspect ratio (ISAr), surface sphericity (ISS), relative distance from ICM to TE (IRD), contact area with TE (ICA); TE cells: number (TN), density (TD), distribution difference (TDD), TE cell roundness (TR), circumference (TC), area (TA) and variance, TE cell aspect ratio (TMM) and variance. The BOV, BCV, and BSA of the blastocyst were positively correlated with clinical pregnancy rate (CPR). The quartile results showed significant differences in CPR when the values were >179 wμm3, 165 wμm3, and 25.8 wμm2, respectively. In terms of ICM, there was no significant difference in CPR among the IV, ISA, IRD, and ICA. However, we found ISAr and ISS had higher CPR in the range of 0.715-0.912 and 0.920-0.943, respectively. In terms of TE, TN is positively correlated with CPR. TD, TDD, TR were not significantly associated with CPR. The pleasing finding is that TC, TA, TMM, and their variances are significantly correlated with CPR. Limitations, reasons for caution The overall quality of blastocysts is relatively good, which is related to the priority thawing of the best blastocysts. Some blastocysts may appear partially out of view, leading to data unavailability and potentially affecting 3D reconstruction. Further exploration and discovery are needed for the spatial conformational features of blastocysts. Wider implications of the findings This work provides a 3D reconstruction system for blastocysts that is closer to clinical applications and discovers new spatial features that are related to clinical outcomes. This enables the study of more dimensional biological characteristics of blastocysts, and our research further promotes the development of embryo reconstruction technology. Trial registration number not applicable

Which factors affect the live birth outcome of the first single euploid frozen-thawed blastocyst transfer in couples with balanced chromosomal translocations?

The objective of this study is to investigate the factors that influence the live birth rate (LBR) of the first single euploid frozen-thawed blastocyst transfer (FBT) cycles after preimplantation genetic testing for structural rearrangements (PGT-SR) in couples with balanced chromosomal translocations (BCT). Single center, retrospective and observational study. A total of 336 PGT-SR and the first single euploid FBT cycles between July 2016 and December 2022 were included in this study. The patients were divided into two groups according to the live birth outcomes. The parameters of the study population, controlled ovarian stimulation cycles, and FBT cycles were analyzed. Multivariable binary logistic regression was performed to find the factors that affected the LBR. The percentage of blastocysts at developmental stage Day 5 compared to Day 6 (51.8% vs. 30.8%; P<0.001) and with morphology ≥BB compared to <BB (49.7% vs. 32.2%; P=0.001) was significantly different between the group that resulted in live births (n=193) and the group that did not (n=143). The results of the multivariable binary logistic regression analysis indicated that the developmental stage (adjusted OR: 2.068, 95%CI 1.291-3.313; P=0.003) and morphology (adjusted OR: 1.697, 95%CI 1.039-2.773; P=0.035) of the blastocyst were significantly correlated with live birth. Patients with blastocysts that reached the developmental stage at Day 5 and had a morphology of ≥BB had a higher likelihood of having a live birth. The developmental stage and morphology of blastocyst affect the live birth outcome of the first single euploid FBT in BCT carriers undergoing PGT-SR.

Should we should consider day 3 blastomere number during single vitrified-warmed blastocyst transfer cycle? A retrospective study

The present study investigated whether day 3 blastomere number has an effect on the clinical outcomes during single vitrified-warmed blastocyst transfer cycles. A total of 3294 vitrified-warmed single day 5 blastocyst transferred cycles were analyzed in this retrospective study from January 2018 to December 2021. The cycles were divided into ≥ 7 and < 7 blastomere groups depending on the day 3 embryo blastomere number. The clinical outcomes were compared between the two groups, moreover multivariate logistic regression analysis was conducted to investigate the correlation between the number of day 3 blastomeres and clinical outcomes. The chi-square test demonstrated that the rates of clinical pregnancy and live birth were significantly higher in the ≥ 7 blastomere group compared to the < 7 blastomere group with respect to single high-quality blastocyst transfer cycles. Conversely, these rates were similar in the two groups with respect to single low-quality blastocyst transfer cycles. These results were confirmed by multivariate logistic regression analysis. However, the miscarriage rate was higher in the < 7 blastomere group than in ≥ 7 group during low-quality blastocyst transfer cycles. These results suggested that day 3 blastomere number should be considered during single vitrified-warmed blastocyst transfer cycles. Thus, blastocsyts derived from ≥ 7 blastomere embryos are preferred when choosing the same quality blastocysts.

Prioritized single vitrified blastocyst to be warmed between grades 3 or 4 blastocyst on day 5 transfer cycles.

Selecting the optimal blastocyst to implant during cryopreservation and warming is critial for in vitro fertilization success. Therefore, the aim of this study was to explore which blastocyst should be prioritized to be thawed when facing a single vitrified blastocyst on day 5 transfer. A retrospective study including 1,976 single vitrified-warmed blastocyst transfer cycles was conducted from January 2016 to December 2020. We found that grade 4 vitrified blastocyst had a higher clinical pregnancy (60.64% vs. 49.48%, P < 0.001) and live birth rates (50.12% vs 39.59%, P < 0.001) than the grade 3 vitrified blastocyst. However, no statistical difference was found between groups in miscarriage rate, birth weight, or gestational age. Besides, the grade 4 vitrified-thawed blastocyst had significant potential to develop into grade 6 blastocyst after further culturing for 16 h (73.68% vs. 48.60%, P < 0.001). The grade 6 transferred blastocyst was markedly higher in both clinical pregnancy rate (61.88% vs. 51.53%, P < 0.001) and live birth rate (50.91% vs. 40.46%, P < 0.001) compared to grade 5 transferred blastocyst. Grade 4 vitrified blastocyst is recommended when facing single vitrified blastocyst on day 5 transfer. More importantly, the "embryonic escape hypothesis" was firstly proposed to reveal the findings.

Effect of development speed and quality of blastocyst on singleton birthweight in single frozen-thawed blastocyst transfer cycles.

Assisted reproductive technology (ART) has revolutionized infertility treatment, leading to a surge in ART-conceived children. Despite its success, ART-born offspring face higher risks of preterm birth (PTB), low birth weight (LBW), and small for gestational age (SGA). The mechanisms behind these outcomes remain unclear, partly attributed to multiple embryo transfers. Recent advancements advocate single blastocyst transfers for improved outcomes. However, the influence of blastocyst quality and development speed on neonatal outcomes is underexplored. This study investigated whether blastocyst development speed and quality affect singleton birthweight when the blastocyst is selected for single frozen-thawed blastocyst transfer (FBT). Data from patients who performed an FBT cycle at our center from July 2011 to June 2021 were collected and analyzed. Based on the inclusion and exclusion criteria, 420 single FBT cycles were assessed. The women were divided into four groups, Group A (day 5, good-quality blastocysts), Group B (day 5, non-good-quality blastocysts), Group C (day 6, good-quality blastocysts), and Group D (day 6, non-good-quality blastocysts) according to the developmental speed and quality of the transferred blastocyst. The birthweight was relatively the highest in Group A, which developed rapidly and transferred good quality blastocysts. However, no significant difference existed among the groups (P>0.05). The prevalence of premature birth (PTB), low birth weight (LBW), very low birth weight (VLBW), or high birth weight (HBW) was similar among the four groups (P > 0.05). No correlation existed between birth weight and blastocyst development speed or quality after adjusting for possible confounders (P > 0.05 respectively). However, the difference in the proportion of males born among the four groups was significant, especially in Group D, which was significantly lower than that in Group A (adjusted odds ratio = 0.461, 95% confidence interval: 0.230-0.921, P< 0.05). This retrospective cohort study suggests that the combined effect of blastocyst development speed and quality on neonatal birthweight is insignificant. The transfer of slow-growing, non-good-quality blastocysts increases the chance of a female baby being born.

Does cleavage stage morphology increase the discriminatory power of prediction in blastocyst transfer outcome?

To evaluate the contribution of the cleavage stage morphological parameters to the prediction of blastocyst transfer outcomes. A retrospective study was conducted on 8383 single-blastocyst transfer cycles including 2246 fresh and 6137 vitrified-warmed cycles. XGboost, LASSO, and GLM algorithms were employed to establish models for assessing the predictive value of the cleavage stage morphological parameters in transfer outcomes. Four models were developed using each algorithm: all-in model with or without day 3 morphology and embryo quality-only model with or without day 3 morphology. The live birth rate was 48.04% in the overall cohort. The AUCs of the models with the algorithm of XGboost were 0.83, 0.82, 0.63, and 0.60; with LASSO were 0.66, 0.66, 0.61, and 0.60; and with GLM were 0.66, 0.66, 0.61, and 0.60 respectively. In models 1 and 2, female age, basal FSH, peak E2, endometrial thickness, and female BMI were the top five critical features for predicting live birth; In models 3 and 4, the most crucial factor was blastocyst formation on D5 rather than D6. In model 3, incorporating cleavage stage morphology, including early cleavage, D3 cell number, and fragmentation, was significantly associated with successful live birth. Additionally, the live birth rates for blastocysts derived from on-time, slow, and fast D3 embryos were 49.7%, 39.5%, and 52%, respectively. The value of cleavage stage morphological parameters in predicting the live birth outcome of single blastocyst transfer is limited.

#37 : Improved Pregnancy Prediction Performance in an Updated Deep-Learning-Based Embryo Selection Model: A Retrospective Independent Validation Study Using 3,960 Single Blastocyst Transfer Cycles

Background and Aims: Generally, the performance of deep learning models is improved by increasing the size of the training dataset. However, to the best of our knowledge, there has been no study on the effect of increasing training data on the performance of pregnancy prediction using the same deep-learning model. Method: A total of 3,960 blastocyst transfer cycles (1 patient, 1 cycle) were retrospectively analyzed. Embryos were stratified according to SART age groups. The quality and scoring of embryos were assessed by iDAScore v2.0 (iDA-V2; Vitrolife, Sweden), v1.0 (iDA-V1; Vitrolife, Sweden), and Gardner grading (GG). The discriminative performance of pregnancy prediction for each embryo scoring model was compared using the area under the curve (AUC) of the receiver operating characteristic curve for each maternal age group. Results: In the AUCs of the &lt; 35 years age group (n = 757) for pregnancy prediction, the AUC of iDAV2 was significantly higher than that of GG (0.718 vs. 0.694, p = 0.015). For the 35-37 years age group (n = 821), the AUC of iDA-V2 was significantly higher than that of iDA-V1 (0.712 vs. 0.696, p = 0.035). In the AUCs of the 41–42 years age group (n = 715), the AUC of iDA-V2 was significantly different from that of GG (0.745 vs. 0.696, P = 0.007). In the &gt; 42 years age group (n = 660) and 38–40 years age group (n = 1,007), there were no significant difference among the groups. Conclusion: The present study suggests that the performance of deep learning models for pregnancy prediction will be improved by increasing the size of the training data. Therefore, in a deep-learning model for pregnancy prediction, continuously collecting training data is an important step for improving the performance of updated AI models.

#129 : The Ratio of Luteal Phase Serum Progesterone and Estradiol Can be Used to Predict Pregnancy in Frozen Embryo Transfer Cycles

Background and Aims: Low serum progesterone (P) levels on day of embryo transfer (ET) and luteal phase have been associated with poorer pregnancy outcome. This study aimed to know if serum estradiol (E2) and P levels during mid and late luteal phase are related with ongoing pregnancy. Method: The serum E2 and P levels from mid luteal phase (5 days after ET) to the day of the [Formula: see text]-hCG check (11 days after ET) in both fresh and frozen embryo transfer (FET) cycles was investigated between January 2019 and December 2021. Eligible patients were reproductive aged women with a normal uterus. Single blastocyst transfer cycles were included. Estradiol valerate (2 mg/bid) was started from day 3 of cycle as hormone replacement and vaginal micronized P (400 mg/bid) was started 5 days before ET in all FET cycles. The 2-degree polynomial fitted data were analysed and logistic linear model and ROC analysis were performed to assess E2 and P4 polynomial coefficients as a predictive test for ongoing pregnancy. Results: A total of 388 patients were included. The overall pregnancy rate was 43.8% and 31.3% for FET and fresh ET, respectively. On day 5 post ET, the serum P levels correlated significantly with ongoing pregnancy and live birth rates, especially in FET cycles. The ROC curve showed that there is a significant day 5 post ET predictive value of serum P4/E2 levels for pregnancy rate, being the AUC (95% CI) = 0.596 (0.539–0.653) for the combination of both fresh and FET cycles; and 0.611 (0.548–0.674) for FET cycles, with best cut-off values of 0.079 and 0.077, respectively. Conclusion: Serum P levels in mid and late luteal phase days are associated with pregnancy outcome both in fresh and frozen ET cycles. Ongoing pregnancies can be predicted using the day 5 post ET serum P4/E2 levels.

#273 : Comparative Analysis of Pregnancy Predictive Potential Using the Deep Learning Blastocyst Scoring Model Calculated from the Single Focus Blastocyst Image and Time-Lapse Image Sequences

Background and Aims: Artificial Intelligence (AI) based embryo evaluation may objective and reduce inter-observer disagreement. Most commercially available AI models use blastocyst morphokinetics from time-lapse monitoring (TLM). Lifewhisperer (LW, FUJIFILM) is an AI-scoring model that uses a single-focus blastocyst image at a single-time point. LW may be more acceptable to many facilities than the TLM model as it does not require a time-lapse incubator. This study analyzed the predictive ability of LW for pregnant embryos and compared it to an AI model based on morphokinetics (iDAscore, Vitrolife) to assess their usefulness. Methods: This retrospective single-center study analyzed 666 vitrified-warmed blastocyst transfer cycles from January 2019 to December 2022. Inclusion criteria were blastocysts that developed within 5 days from insemination (maximum 120 h) using EmbryoScope+ (Vitrolife), intracytoplasmic sperm injection (ICSI) cycle, and a single-blastocyst transfer cycle. LW score (1.0–9.9) was calculated from single-focus blastocyst images taken before vitrification, while iDAScore (1.0–9.9) was calculated from time-lapse image sequences taken at 11 focal every 10 min after ICSI. We calculated the odds ratio for pregnancy and ROC analysis to compare these models. Results: The mean score was higher in pregnant blastocysts than in non-pregnant blastocysts in both models (LW: 7.47 vs. 6.72, p&lt;0.01; iDAScore: 8.50 vs. 8.04, p&lt;0.01, Willcoxon-test). The odds ratio (95% confidence interval) for pregnancy was 1.19 (1.10–1.28) for LW and 1.48 (1.27–1.74) for iDAScore, with the odds for clinical pregnancy increasing with higher scores (p&lt;0.01). ROC curve analysis showed that the AUC values were 0.60 for LW and 0.62 for iDAScore. There was no significant difference in the predictive ability for pregnant blastocysts (p=0.51). Conclusions: LW allowed objective score calculation from a single focus at single time point blastocyst images without TLM. Moreover, in day 5 blastocyst, LW and iDAscore had comparable predictive pregnancy ability.

#193 : Comparison of the Different Expression of OCT-4, GATA-3 and Clinical Pregnancy Outcome Between the Day 5 and Day 6 Blastocysts

Background and Aims: In common experience of in vitro-fertilization (IVF) cycle, blastocysts formed at Day 5 (D5) are regarded as higher quality and are more desirable for embryo transfer compared with those formed at Day 6 (D6). How those delayed D6 embryo differs from D5 embryo is less discussed. This study aimed to elucidate the cell content distinguished by immunofluorescent (IF) staining between the same grade of D5 and D6 blastocysts that might link to the clinical pregnancy outcome in frozen–thawed embryo from different day of blastocyst formation. Method: The retrospective study included 1327 frozen-thawed single blastocyst transfer (SBT) cycles in the Taipei Fertility Center during March 2020 to December 2022. All D5 (D5-SBT) and D6 (D6-SBT) frozen-thawed SET cycles (n=1327) were separated to non-PGS (n=671) and PGS-euploid (n=656) groups, then assigned to high grade (AA, AB, BA, BB) and low grade (BC, CB, CC). Aneuploidy and mosaicism embryo are excluded. For cell content analysis, pluripotent marker OCT-4 initially expressed in all blastomeres but restricted to the inner cell mass (ICM) of the blastocyst and downregulated in the trophectoderm (TE). GATA-3 is a TE specific marker which increases during pre-implantation embryo development. The cell number, OCT-4 and GATA-3 expression of same grade frozen-thawed D5 (n=14) and D6 (n=14) blastocysts were analyzed with IF staining. D5 extensively cultured to D6 (n=10) were used as the control group of regularly development. Cell numbers of TE and ICM region were examined by OCT-4 and GATA-3 IF detection. The total cell number was visualized with DAPI staining. Results: According to staining results, there were no significant differences in total cell number, TE and ICM cell number between the same grade D5 and D6 blastocysts. However, TE cell number significantly increased in D5 extensively cultured blastocysts, indicating higher proliferative capacity in TE cells from D5 blastocysts. In the clinical data of the non-PGS group, chemical pregnancy rate (HCG+) and clinical pregnancy rate (SAC+) of high grade D5-SBT were significantly increased compared with high grade D6-SBT (HCG+: 69.1% versus 47.0%, P&lt;0.001; SAC+: 63.0% versus 43.4%, P=0.001). In the PGS-euploid group, the chemical pregnancy rate (HCG+) showed significantly increased in high grade D5-SBT compared with high grade D6-SBT (69.5% versus 60.0%, P=0.047). The clinical pregnancy rate (SAC+) was significantly higher in high grade D5-SBT compared with high grade D6-SBT (65.5% versus 52.5%, P=0.009). The ongoing pregnancy rate was significantly higher in high grade D5-SBT compared with high grade D6-SBT (57.6% versus 43.3%, P=0.005). Conclusion: According to the IF data in this study, we demonstrated that the number of GATA3-positive TE cells were significantly decreased in D6 blastocyst compared with D5 extensively cultured blastocysts. Due to decreased proliferative capacity in high grade D6 blastocyst, transfer of high grade D5 blastocyst would exhibit higher ongoing pregnancy rate than D6 blastocyst.

#270 : Single-Center Retrospective Cohort Analysis: Preimplantation Genetic Testing for Monogenic Disorders (PGT-M) for Monogenic Nephropathy

Background and Aims: Hereditary nephropathy, including monogenic nephropathy, is an important cause of renal insufficiency and end-stage renal disease. Therefore, genetic blockade is necessary for couples with monogenic nephropathy. Following routine application of prenatal diagnosis, preimplantation genetic testing for monogenic disorders (PGT-M) has been applied to the genetic blockade of monogenic disease patients. The purpose of this study is to retrospectively analyze genetic counseling process for patients with nephropathy-related disease and provide clinical overviews of patients with monogenic nephropathy who underwent PGT-M. Method: A single-center retrospective cohort study was conducted at Center for Reproductive Medicine, Shandong University from January 2014 to December 2022. 352 couples with nephropathy-related disease were included in the cohort totally. Statistical analysis was performed using Statistical Package for Social Science software 26.0. Results: Of the 352 couples with nephropathy-related disease, 291 underwent genetic counseling, followed by 180 accepting genetic screening. 104 couples with monogenic nephropathy indications proceeded with PGT-M, including 91 of autosomal dominant inheritance, 9 of autosomal recessive inheritance, 3 of X-linked dominant inheritance, and one of X-linked recessive inheritance. 498 blastocysts were tested by PGT-M combined with preimplantation genetic testing for aneuploidy (PGT-A), making 72 transferable embryos, 249 non-transferable embryos, 72 genetic counseling embryos and 7 amplification failedembryos. Finally, 80 vitrified-thawed single blastocyst transfer cycles were performed. Live births occurred in 38 women, of which 37 transferred embryos with non-pathogenic genotypes. The results of prenatal diagnosis of all newborns were consistent with the testing results for embryos transferred. The cumulative live birth, biochemical pregnancy, clinical pregnancy, ongoing pregnancy and pregnancy loss rates were 36.54%, 56.73%, 49.04%, 7.69%, and 22.03% respectively. Conclusion: PGT-M is an effective means of genetic blockade for couples with monogenic nephropathy. The absence of genetic abnormalities detected by prenatal diagnosis in healthy newborns without monogenic nephropathy also underscore its validity.