Intrauterine administration of hCG has been considered as a promising IVF add-on before embryo transfer to improve fertility outcomes. A Cochrane review and four more recent systematic reviews all showed improved clinical pregnancy rates and/or live birth rates following intrauterine administration of hCG, however, a high unexplained heterogeneity was also present. To investigate the effectiveness and safety of intrauterine administration of hCG before embryo transfer in participants undergoing IVF. Individual participant data meta-analysis (IPD-MA) is recognized as the gold standard for evidence synthesis due to its ability to harmonize the data and to investigate treatment-covariate interactions. In addition, with recent experiences of guideline development and systematic review production raising increasing concerns about the trustworthiness of randomized controlled trials (RCTs) in women's health research, an IPD-MA provides a unique opportunity to summarize the best available and most trustworthy evidence on this topic. We searched MEDLINE, Embase, Cochrane Gynaecology and Fertility Group Specialised Register, Cochrane Central Register of Controlled Trials, PsycINFO, and clinical trial registries without language restrictions up to January 2026. Inclusion criteria included RCTs comparing intrauterine administration of hCG before embryo transfer versus placebo or no intervention in participants undergoing IVF. The IPD Integrity tool and the TRACT checklist were used to evaluate the trustworthiness of studies with and without IPD, respectively. Both one-stage and two-stage random-effect IPD meta-analyses were performed with one-stage being the primary analysis. We detected 28 RCTs, of which 7 RCTs with IPD involving 2244 participants were included. All seven RCTs with IPD met trustworthiness criteria and six RCTs had overall low risk of bias. All RCTs without IPD did not meet trustworthiness criteria. IPD-MA showed intrauterine administration of hCG before embryo transfer did not improve live birth rates (7 RCTs, 2244 participants, odds ratio [OR] 0.99, 95% CI 0.83-1.19) or clinical pregnancy rates (7 RCTs, 2244 participants, OR 1.04, 95% CI 0.83-1.31). Studies without IPD showed different results from those with IPD for live birth (1.99, 0.72-5.50, P for interaction <0.001) and clinical pregnancy (1.87 (1.48-2.35), 17 RCTs without IPD, 3152 participants, P for interaction 0.005). Our IPD-MA has shown that intrauterine administration of hCG before embryo transfer is unlikely to improve the chance of clinical pregnancy and live birth. In the comparison between studies with IPD and without IPD, we found that none of the RCTs without IPD met trustworthiness criteria but showed a significant improvement in clinical pregnancy. We therefore suggest that intrauterine administration of hCG should not be offered as an IVF add-on in practice. PROSPERO (CRD42020177397).

Resveratrol supplementation and assisted reproduction outcomes: A systematic review and meta-analysis.

Intracytoplasmic sperm injection (ICSI) has not been shown to be superior to conventional insemination for non-male factor infertility indications in cycles using fresh sperm, however fertilization and reproductive outcomes have not been explored in the setting of cryopreserved sperm. This retrospective cohort study included 4413 patient couples between 2010 and 2021 that underwent autologous retrieval cycles utilizing cryopreserved donor sperm with linked subsequent fresh and frozen single blastocyst transfers at a large network of private practice fertility clinics in the United States. The primary exposure was insemination method; conventional insemination or ICSI. The primary outcome of interest was fertilization percentage. Secondary outcomes included percentages of blastulation, total fertilization failure, clinical pregnancy, and live birth. Adjusted associations were evaluated accounting for relevant confounders. At first retrieval, patients in the conventional insemination group had a higher mean number of oocytes retrieved (14.29 [7.70] vs. 13.58 [8.84]) and number of fertilized oocytes (8.70 [5.27] vs. 7.89 [5.88]) compared to the ICSI group. Mean fertilization and blastulation percentages were also higher in those who utilized conventional insemination (61% and 45%) compared to those who utilized ICSI (56% and 34%). After multiple retrievals, adjusted associations examining fertilization method and outcomes showed conventional insemination was associated with a 12% (95% CI [0.05, 0.19]) higher mean blastulation percentage, increased likelihood of clinical pregnancy (RR 1.64; 95% CI [1.27, 2.12]), and higher live birth (RR=1.45; 95% CI [1.06, 2.00]) compared to ICSI. Use of conventional insemination in cycles involving cryopreserved donor sperm was associated with improved blastulation and increased likelihood of clinical pregnancy and live birth compared to ICSI. These findings suggest that routine ICSI use in this population may warrant reconsideration and that conventional insemination could remain an appropriate option in selected cases utilizing cryopreserved donor sperm.

Human embryo selection in in vitro fertilisation (IVF) treatments is traditionally based on evaluating cell number, morphology, and fragmentation to select the most viable embryos. However, this static evaluation method has limitations, as it captures only a snapshot of the embryo at a single time point. Recent advancements in time-lapse imaging and artificial intelligence (AI) have improved embryo assessment by enabling dynamic and continuous observation of embryonic development.This retrospective cohort study aimed to evaluate morphometric and morphokinetic parameters of 102 human embryos cultured during IVF cycles. Embryos were included if they reached the blastocyst stage on Day 5 and were selected for fresh single embryo transfer. Morphological and morphokinetic parameters were assessed using time-lapse technology to compare embryos resulting in clinical pregnancy and those that did not.Clinical pregnancy was achieved in 47.1% of transfers. Although no significant differences were observed in blastocyst area, diameter, or inner cell mass (ICM) size between embryos that implanted (P+) and those that did not (P-), trends toward larger dimensions were observed in the P+ group. Morphokinetic parameters showed slightly faster developmental kinetics in P+ embryos, although not significantly.Morphokinetic scores were calculated using time-lapse embryo evaluation systems (KIDScore D5 and iDAScore, Vitrolife). iDAScore values were significantly higher in implanted embryos. iDAScore, which incorporates AI-based scoring, showed better predictive performance compared with KIDScore in ROC and logistic regression analyses, indicating its potential as a reliable tool for embryo selection. These findings support the use of AI-based morphokinetic analysis for improved embryo selection in IVF.

Natural versus GnRHa-HRT cycle for FET in tubal infertility with prior failed natural cycles: a propensity score-matched retrospective cohort study.

This study compared the traditional blastocyst grading system with quantitative measurements of blastocyst expansion in relation to total pregnancy rate, implantation rate, and clinical pregnancy rate. A retrospective analysis was performed using data collected from patients undergoing frozen single embryo transfer cycles between 2021 and 2024. Single vitrified-warmed blastocyst transfers in self-patients were included, whereas cleavage-stage transfers and donor programs were excluded. All blastocysts were morphologically graded using the Gardner grading system. The degree of expansion was assessed morphometrically by measuring the inner diameter of the blastocyst from images obtained at the equatorial plane during embryo transfer, using Hamilton Thorne laser software. Multiple statistical tests were applied to analyze both qualitative and quantitative assessments of blastocysts in relation to clinical outcomes. When comparing morphological parameters such as the quality of inner cell mass (ICM), trophectoderm (TE), and blastocyst expansion level, ICM and TE quality were found to significantly influence clinical outcomes. In comparing qualitative and quantitative (mean diameter) assessments of blastocysts with clinical outcomes, TE grade and blastocyst expansion level assessed qualitatively showed significant effects, whereas ICM quality and quantitative expansion measurements did not demonstrate statistical significance. Qualitative assessments of TE grade and blastocyst expansion level appear to be stronger predictors of clinical outcomes than ICM grade and morphometric assessment of blastocyst expansion. Larger datasets, including morphometric evaluation of ICM and TE cells, are recommended to clarify the predictive value of morphometric parameters.

Miscarriage is a common complication of pregnancy, and it is defined as spontaneous pregnancy loss before the fetus reaches viability. However, there are no clear pathological factors identified as causes of recurrent miscarriage in some cases. Preimplantation genetic testing for aneuploidy (PGT-A) has been shown to have some advantages in the live birth rate in limited populations with a favorable prognosis. Hence, we investigated whether PGT-A improves pregnancy outcomes in patients with recurrent pregnancy loss. We conducted a retrospective study including patients with a history of recurrent pregnancy loss from December 2021 to June 2022 receiving assisted reproduction therapy in the first medical center of the Chinese PLA General Hospital. The patients were divided into PGT-A and non-PGT-A groups, and we compared the pregnancy outcomes between the PGT-A and non-PGT-A groups. PGT-A significantly increased the clinical pregnancy rate per embryo transfer (ET) (58.7 vs. 32.3%, p = 0.023) and live birth rate per ET (50.0 vs. 25.8%, p = 0.034). However, there were no differences in biochemical pregnancy rates per ET (69.6 vs. 51.6%, P = 0.111), biochemical pregnancy loss rates (15.6 vs. 37.5%, p = 0.089), and miscarriage rate per clinical pregnancy (11.5 vs. 20.0%, p = 0.511) between the PGT-A and non-PGT-A groups. PGT-A was associated with significant improvements in clinical pregnancy and live birth rates in patients with recurrent pregnancy loss. This study was registered at the Chinese Clinical Trial Registry (ChiCTR2200056991 http//www.chictr.org.cn/). Registration Date 20,220,225.

Progestin-primed ovarian stimulation (PPOS) has emerged as an alternative to GnRH-antagonist protocols in IVF, yet its impact on embryo chromosomal competence remains controversial. Evidence is particularly limited regarding whether PPOS influences blastocyst euploidy rates and key clinical outcomes in PGT-A cycles, and whether these effects vary according to maternal age and ovarian reserve status. This retrospective cohort study included 1,843 PGT-A cycles (666 PPOS, 1,177 GnRH antagonist) performed at a single tertiary IVF center between January 2016 and January 2024. Controlled ovarian stimulation was performed with either oral medroxyprogesterone acetate or daily cetrorelix, followed by vitrification of all biopsied blastocysts and subsequent frozen embryo transfer. Primary outcomes were blastocyst euploidy and clinical pregnancy rates. Secondary outcomes included embryological parameters, miscarriage, live birth, and cumulative pregnancy rates. Subgroup analyses were performed according to maternal age and ovarian reserve. The mean age was 37.64±4.48 years in the PPOS group and 37.80±3.49 years in the GnRH-antagonist group; age and other baseline characteristics were comparable between groups. PPOS cycles had a shorter stimulation duration (median 8 vs. 9 days, p = 0.001), with comparable gonadotropin requirements and embryological outcomes. Euploidy (32.6% vs. 32.1%, p = 0.653), mosaicism, and aneuploidy rates did not differ significantly. Clinical pregnancy, live birth, and cumulative pregnancy rates were equivalent. PPOS and GnRH antagonist protocols yield comparable embryological and clinical outcomes in PGT-A cycles, including in advanced maternal age and diminished ovarian reserve subgroups. With its shorter stimulation duration and cost-effectiveness, PPOS is a valid alternative when fresh transfer is not planned.

The effect of hyoscine N-butylbromide on embryo transfer: a randomized clinical trial.

Operator-dependent laboratory tasks-embryo selection, vitrification and warming, and intracytoplasmic sperm injection (ICSI)-have been the principal targets of IVF laboratory automation, and a fourth strand of work, integrated end-to-end laboratory automation, has produced its first peer-reviewed clinical evidence in 2026. Clinician-side automation in the same ART cycle has an older, broader literature that provides a useful comparator for what laboratory-side automation has and has not yet achieved. To synthesize the published evidence on automation of these laboratory-side task domains; to distinguish what has been demonstrated in randomized or large multicenter studies from what remains in the proof-of-concept phase; to compare the maturity of laboratory-side automation with the older, broader literature on clinician-side automation; to articulate the structural condition-parallel development of clinician-side and laboratory-side automation-that the available evidence suggests would have to be met before any of these technologies could deliver the system-level outcome gains they promise; and to identify a complementary observation that the laboratory tasks for which automation has been most actively developed are not those in which operator competence translates most directly into clinical outcome, with preimplantation genetic testing (PGT) biopsy and tubing as the conspicuous omission. A narrative review of PubMed-indexed primary studies, ESHRE/Alpha consensus documents, and Cochrane reviews was conducted, with emphasis on randomized comparisons (Hajek 2021 for vitrification, Illingworth 2024 for AI selection) and large registry or multicenter datasets where available. The 2026 Human Reproduction proof-of-concept report on integrated end-to-end laboratory automation (Chavez-Badiola and colleagues) is treated as the current state of evidence for that domain. (i) Deep-learning embryo grading reproducibly outperforms individual embryologists in retrospective benchmarks across multiple algorithms and centers, but the only published randomized trial failed to demonstrate non-inferiority of deep-learning selection over standard morphology in clinical pregnancy, and the Cochrane review of time-lapse imaging found no evidence of differences in live birth or clinical pregnancy. The realistic value proposition is workflow standardization rather than improved clinical outcome. (ii) Closed semi-automated vitrification (Gavi) achieves clinical and survival outcomes equivalent to manual Cryotop in a multicenter RCT; one-step warming protocols offer substantial workflow gains without compromising survival. (iii) Automated and remotely-operated ICSI have produced healthy live births in proof-of-concept clinical work but remain very early in their clinical adoption curve. (iv) Integrated end-to-end laboratory automation has produced its first proof-of-concept clinical evidence in a single sponsor-conducted pilot in 11 selected patients, in which automated arms were numerically outperformed by manual sibling-oocyte controls; randomized comparison and independent replication are not yet available. (v) Across all four domains, the clinical endpoint of an ART cycle is jointly determined by laboratory-side and clinician-side performance; this co-dependence, examined in detail in the "The clinician's perspective: where automation has earned trust and where it has not yet" section, places a structural constraint on the system-level benefit any single laboratory-side technology can be expected to deliver. A within-laboratory parallel of this asymmetry is also observed: automation effort has converged on the technically tractable laboratory tasks (ICSI, vitrification, and embryo selection) rather than on the tasks with the highest operator-competence elasticity (PGT biopsy and tubing). Across the four laboratory-side task domains, the level of clinical evidence available in 2026 is uneven and the maturity gradient is asymmetric with respect to clinician-side automation, which has a longer accumulated evidence base in the same ART cycle. Rather than disappearing, the embryologist's role is shifting toward verification, exception-handling, and quality oversight. The substantive observation a focused review can make in 2026 is that the system-level benefits projected for laboratory-side automation appear bounded by the slower pace of clinician-side automation development and that the asymmetry between the two halves of the cycle, together with a parallel asymmetry inside the laboratory itself, conditions what any laboratory-side technology can be expected to deliver at the level of patient outcome.

Spontaneous ovarian endometrioma rupture typically presents with acute abdominal pain, a condition often complicated by tissue edema and pelvic adhesions that increase surgical difficulty. This study aims to evaluate the impact of surgical expertise on long-term outcomes in patients with a history of spontaneous ovarian endometrioma rupture. This is a retrospective cohort study at Peking Union Medical College Hospital between January 2012 and December 2022, which analyzed patients with spontaneous ovarian endometrioma rupture who underwent surgery. Patients were categorized into specialist or non-specialist surgery groups based on the expertise level of the surgical team. Clinical characteristics, postoperative treatment and recurrence data were collected and compared. Of the 122 patients, 32 were treated by specialists and 90 by non-specialists. All participants received laparoscopic surgery. Baseline characteristics and intraoperative findings were comparable between the two groups. Elective surgery was performed more frequently in the specialist group (81.2%) than in the non‑specialist group (45.6%, p = 0.001). The crude recurrence risk was 15.6% (5/32) in the specialist group, compared with 33.3% (30/90) in the non-specialist group (p = 0.264). Time-to-event analysis demonstrated a significantly lower 10-year cumulative recurrence risk in the specialist group (log-rank p = 0.033). In multivariable Cox regression analysis adjusting for surgery timing, maximum ovarian endometrioma diameter, rASRM score, and treatment duration, specialist surgery remained associated with a lower hazard of recurrence (adjusted HR 0.378, 95% CI 0.140-1.021), although this did not reach statistical significance (p = 0.055). None of the other covariates were significantly associated with recurrence. No between‑group difference was observed in clinical pregnancy rates. For patients with a history of spontaneous rupture of ovarian endometrioma, surgery performed by specialists with more extensive experience in endometriosis may be associated with a lower long-term recurrence risk. This finding should be interpreted with caution given the borderline statistical significance after Cox adjustment. Nonetheless, the observed trend highlights the potential importance of surgical expertise and the need for specialized training in endometriosis management.

To investigate the association between embryo transfer (ET) catheter maneuvers on clinical pregnancy (CP) and live birth (LB). This retrospective cohort study included all in vitro fertilization and intracytoplasmic sperm injection cycles resulting in fresh or frozen ET at a single academic institution from 2013 to 2024. Catheter maneuvers were categorized as non-afterload or afterload. Non-afterload techniques included direct (straight outer sheath and inner catheter inserted together without manipulation), outer sheath curved, outer sheath extended, and outer sheath both curved and extended. Afterload techniques included: straight afterload (outer sheath retained, inner catheter removed, embryo loaded through another inner catheter), and curved afterload (curved outer sheath retained, inner catheter removed, and embryo loaded through another inner catheter). Adjusted log binomial regression assessed associations between ET catheter maneuvers and CP and LB. Among 7882 ETs, 46.0% were direct, 1.9% curved, 8.8% extended, 10.2% curved and extended, 6.7% straight afterload, and 26.5% curved afterload. Afterload ETs were associated with lower adjusted relative risk (aRR) of CP (aRR 0.91, 95% confidence interval [CI] 0.85-0.98) and LB (aRR 0.88, 95% CI 0.81-0.96) compared to a direct technique. Curved afterload ETs had a lower aRR of both CP (aRR 0.91, 95% CI 0.85-0.98) and LB (aRR 0.92, 95% CI 0.86-0.99). Straight afterload ETs were associated with lower LB (aRR 0.89, 95% CI 0.81-0.99), but not CP (aRR 0.93, 95% CI 0.85-1.02). Non-afterload variations were not associated with outcome differences. ET afterload techniques are associated with lower CP and LB rates compared to a direct technique.

Do the genetic and clinical outcomes of monopronuclear blastocysts (MPBs) differ between standard insemination and intracytoplasmic sperm injection cycles, and what do these differences imply for risk stratification and individualized clinical decision-making? IVF-derived MPBs demonstrate significantly lower rates of uniparental inheritance than ICSI-derived MPBs (96.9% vs 65.9%) biparental inheritance (P < 0.001), with comparable clinical and neonatal outcomes to 2PN blastocysts following transfer of euploid biparental embryos. A proportion of monopronuclear (1PN) zygotes can develop into euploid blastocysts and, following transfer, result in healthy live births, yet these embryos are widely discarded following fertilization check due to atypical pronucleation. The mechanisms underlying 1PN formation are varied and include asynchronous pronuclear formation, early pronuclear fusion, and premature pronuclear breakdown, meaning a subset may represent normally fertilized diploid zygotes missed at static assessment. Retrospective cohort study of 1PN embryos (N = 13203) derived from IVF (n = 5266) or ICSI (n = 5464) inseminations across 10730 cycles performed at multiple Australian clinics between January 2010 and December 2023. Embryos were defined as 1PN by the appearance of a single pronucleus at fertilization check 16-18 h post-insemination. Time-lapse footage was reviewed on Day 3 to identify late appearing 1PNs and exclude late second pronucleus appearance. Suitable blastocysts underwent trophectoderm biopsy for pre-implantation genetic testing for aneuploidy (PGT-A) and short tandem repeat (STR)-based biparental inheritance testing; only euploid embryos with confirmed biparental inheritance were available for frozen embryo transfer. Outcomes assessed included ploidy, biparental inheritance, blastocyst development, utilization, morphokinetics, pregnancy, live birth, and maternal and neonatal outcomes. IVF-derived MPBs had similar aneuploidy rates to two pronuclei (2PN) embryos (37.3% vs 33.9%) and 440/454 (96.9%) demonstrated biparental inheritance. ICSI-derived MPBs had higher aneuploidy rates (45.5% vs 31.5%, P < 0.05) and only 108/164 (65.9%) had biparental inheritance. Uniparental inheritance was predominantly maternal (IVF 92.8%; ICSI 94.6%). Both IVF and ICSI MPBs were less likely to reach blastocyst stage by Day 5 than 2PN embryos (IVF 19.3% vs 63.3%; ICSI 9.7% vs 60.6%, P < 0.05), and biparental IVF-1PN zygotes were more likely to have more nucleoli compared with uniparental IVF-1PN zygotes (P = 0.008). For embryos with confirmed biparental inheritance, there was no significant difference in clinical pregnancy, ongoing pregnancy, live birth rates, or neonatal outcomes compared with 2PN blastocysts. In approximately one in six cycles containing a 1PN embryo, no utilizable 2PN embryo were available (IVF 15.6%; ICSI 16.7%), with the 1PN embryo representing the sole option for embryo utilization. Retrospective single-entity design introduces potential selection bias and limits generalizability. Uniform protocols across sites preclude the level of evidence required for formal guideline revision. Differential use of time-lapse imaging for ICSI versus static assessment for IVF embryos may contribute to differences in 1PN identification rates between fertilization methods. The STR-based biparental classification platform has not been validated against an orthogonal technology for parental origin calling in 1PN embryos, and the possibility of triploid misclassification or absorption into unreported inconclusive outcomes cannot be excluded. These findings support a risk-stratified approach to MPB management based on fertilization method. IVF-derived MPBs meeting specific morphological and developmental criteria demonstrate a low-risk profile that warrants reconsideration of genetic testing requirements and may inform individualized consent discussions, particularly where 2PN embryos are unavailable. ICSI-derived MPBs carry a substantially higher risk of uniparental inheritance and comprehensive genetic testing remains indicated. No funding was attached to this study. The authors declare no conflict of interest. N/A.

To develop and validate a simple predictive model based on Day 3 embryo morphology to guide blastocyst culture strategy and optimize transfer outcomes for women of advanced maternal age (AMA). This retrospective study analyzed a total of 6840 cleavage-stage embryos from 1102 fresh oocyte retrieval cycles with subsequent blastocyst culture in AMA patients. Key parameters including the number of oocytes retrieved, Day 2 and Day 3 cell numbers, embryo fragmentation, embryo grade, and the number of high-quality Day 3 embryos were assessed. Their associations with the blastocyst formation rate (BR), high-quality blastocyst formation rate (HBR) and clinical outcomes were evaluated. Logistic regression identified the number of high-quality Day 3 embryos as a pivotal independent predictor. A threshold of ≥ 4 high-quality embryos was established. For cycles meeting this criterion, the risk of having no Day 5 transferable blastocyst was 19.30%. Within this group, Day 5 blastocyst transfer was associated with significantly higher clinical pregnancy and live birth rates, a lower multiple pregnancy rate, and improved neonatal outcomes (higher gestational age and birth weight) compared to Day 3 cleavage-stage transfer. The threshold showed good predictive performance in a temporally separated validation cohort (AUC 0.91). In AMA patients, a threshold of ≥ 4 high-quality Day 3 embryos may serve as a practical, low-cost criterion to guide blastocyst culture and elective single blastocyst transfer. The approach is associated with favorable clinical and neonatal outcomes but requires prospective validation in unselected populations.

By reducing the duration of the vitrification-warming procedure to 1 min does ultra-rapid vitrification-warming (URV/W) effectively maintain oocyte viability and improve clinical outcomes compared to conventional vitrification-warming (CV/W) timing (14 min) and what is the effect of the two procedures on cellular stress? URV/W shortens procedure time, reduces cryoprotectant exposure, improves oocyte survival, and is associated with fewer transcriptomic alterations in oocytes than CV/W. CV/W techniques require extended cryoprotectant exposure and micromanipulation, which elevate cellular stress and the risk of cryoinjury. URV/W procedures address these challenges by reducing exposure and manipulation, though comparative data on clinical outcomes and transcriptomic signatures in human oocytes remain limited. The study was performed between August 2024 and December 2024 and included a clinical cohort and a transcriptomic cohort to provide a thorough assessment of the effects of cryopreservation methodology on oocyte and embryo viability, development, and cellular stress. The clinical cohort comprised 1077 oocytes used to evaluate clinical outcomes following CV/W and URV/W. The study also included a prospective analysis involving 68 oocytes from 4 donors in the transcriptomic cohort. Oocytes and trophectoderm biopsy samples from blastocyst-stage embryos were assigned to three groups: fresh, CV/W, and URV/W. The clinical study was performed using a total of 1077 oocytes from 46 donors, which were matched and allocated for the comparison of clinical outcomes between CV/W (n = 519) and URV/W (n = 558). Following vitrification-warming, the oocytes were fertilized via ICSI for assessment of embryo development and clinical outcomes. In the transcriptomic cohort of the study, transcriptomic testing and analysis were performed as part of the prospective analysis to compare CV/W and URV/W in terms of their effectiveness in oocyte freezing and warming, their impact on embryo development, and their effects at the molecular level. A total of 68 samples were obtained from 4 donors, including eight oocytes and eight trophectoderm biopsy samples from each of the three groups. These samples were analyzed to investigate the cellular effects of cryopreservation-induced stress through transcriptomic profiling. The single-cell transcriptomic study included preparation of cDNA libraries followed by next-generation sequencing to investigate differential gene expression across oocytes and embryonic trophectoderm cells in the three groups. This method allowed for the comprehensive monitoring of transcriptional activity, enabling the detection and quantification of mRNA molecules to evaluate the transcriptomic signatures of the study groups. In addition, functional enrichment analyses of up- and downregulated genes were conducted and classified based on gene ontology to identify potential pathways associated with embryo quality and cellular stress. Transcriptomic analysis indicated that gene expression patterns following URV/W were more similar to fresh oocytes than those undergoing CV/W. Differences in gene expression patterns among blastocysts from the three groups were minimal, as the total number of differentially expressed genes was limited. Oocytes subjected to URV/W demonstrated a significantly higher survival rate, lower post-ICSI degeneration, and produced more high-quality Day-5 blastocysts compared to those vitrified using CV/W methods (P < 0.001 for all comparisons). These findings are unlikely to be solely attributable to differences in procedural timing, as fertilization, cleavage, euploidy, clinical pregnancy, and live birth rates were comparable between groups (P > 0.05 for all comparisons). All oocyte samples donated (1145) for research purposes were included in the study without quality-based selection. Only embryos reaching the blastocyst stage on Days 5 or 6 using the URV/W method were included in the transcriptomic analysis. Embryos not reaching these stages were excluded. Consequently, only data from embryos with optimal development and good quality were analyzed, and compared among the three groups. Obtaining cDNA in single-cell studies is a novel and challenging process, particularly due to the limited availability of RNA. While advanced clinical evaluations can still be conducted on biopsied oocytes and embryos, the failure to obtain cDNA from the same samples may result in incomplete data, which can limit the overall scope and outcomes of the study. The comprehensive single-cell transcriptomic data obtained from this expanded dataset will help delineate pathways altered by different vitrification methods, providing critical insights into their efficacy and potential risks in clinical practice. Additionally, the findings will illuminate key genes and pathways involved in embryonic stress, enabling the development of more cost-effective, targeted gene panels for evaluating these factors. This study was funded by the Sanatórium pre liečbu neplodnosti SPLN's, Ovogene and Mikrogen Genetic Diagnosis Laboratory's own resources. A.V.P. is a Medical Science Liaison for Kitazato Corporation-Dibimed. His role in the study was strictly scientific and unrelated to any commercial interest. All the other co-authors declare no conflicts of interest. n/a.

This study aimed to develop an artificial intelligence-based scoring system to prioritize mosaic embryos according to live birth outcomes. This multicentre, observational, retrospective study included 264 transferred mosaic embryos from 2583 PGT-A (Preimplantation Genetic Testing for Aneuploidies) cycles performed between January 2017 and January 2023. Trophectoderm (TE) biopsies from day-5 (D5) or day-6 (D6) blastocysts were analysed using Next-Generation Sequencing (NGS) (VeriSeq, Illumina®, San Diego, CA, USA). Biopsied embryos were vitrified and subsequently transferred. Clinical, embryological, and laboratory variables were collected to build predictive machine learning models for live birth. Models excluding cohort-invariant variables were refined to derive the final scoring system. Among mosaic embryos, biochemical, clinical pregnancy, and live birth rates were 50.75%, 41.66%, and 36.36%, respectively. The best-performing model, validated through tenfold cross-validation, identified embryo quality and biopsy day as the most influential predictors (42% and 34% weights, respectively), while mosaicism-related factors such as monosomy/trisomy (18%) and mosaicism degree (6%) had lower influence. The resulting score suggests prioritizing high-quality embryos biopsied on D5, as the type and level of mosaicism play a minor role in gestational potential, except when comparing embryos of similar quality where lower mosaicism levels and absence of monosomy are advantageous. The AI-derived score highlights embryo quality as the primary determinant of success in mosaic embryo transfer, supporting prioritization of high-quality, D5-biopsied embryos to improve live birth outcomes in ART.

Does a natural cycle result in higher clinical pregnancy rates (CPR) with foetal heartbeat compared to an artificial cycle for frozen-thawed embryo transfer (FET) preparation in ovulatory women? The CPR with foetal heartbeat did not differ between natural and artificial cycles in ovulatory women undergoing FET. Several protocols for endometrial preparation have been developed for the increasing number of FET cycles in reproductive medicine. In natural cycle FET (NC-FET), spontaneous ovulation is used to time the embryo thawing and transfer, while in artificial cycle FET (AC-FET), endometrial preparation involves sequential oestrogen and progesterone administration. Current evidence on pregnancy rates does not favour one regimen over the other in women with regular ovulatory cycles. We conducted a multicentre, open-label, randomised trial comparing NC-FET with AC-FET across five Belgian fertility centres. Between October 2018 and October 2024, 561 women were randomised (1:1) using a computer-generated allocation after written informed consent. The primary outcome was CPR with foetal heartbeat per cycle analysed on an intention-to-treat basis. Secondary outcomes included endometrial thickness, number of clinic visits for FET cycle monitoring and the rates of (biochemical) pregnancy, ongoing pregnancy, live birth, miscarriage, ectopic pregnancy, multiple pregnancy and cycle cancellation. Obstetric outcomes were recorded for all ongoing pregnancies. Women aged 18-45 with regular ovulatory cycles and normal uterine cavities undergoing FET after vitrification and warming of one or two day-3 embryos or blastocysts were included. In NC-FET, spontaneous ovulation was detected by serial ultrasounds and serum LH and oestradiol measurements. In AC-FET, oestradiol valerate (6 mg/day) was administered from cycle day 2 (increased to 8 mg/day after 1 week if endometrial thickness was <7 mm) and micronized progesterone (600 mg/day) was initiated once endometrial thickness reached ≥7 mm. Clinical pregnancy rates with foetal heartbeat were similar between NC-FET and AC-FET in both intention-to-treat (33.1% [94/284] vs 28.9% [80/277]; RR 1.15, 95% CI 0.89, 1.47) and as-treated analyses (34.3% [97/283] vs 31.8% [77/242]; RR 1.08, 95% CI 0.85, 1.38). Cycle cancellations were less frequent in NC-FET (3.9% vs 9.4%; RR 0.41, 95% CI 0.21, 0.82), but NC-FET required more monitoring visits (mean 3.0 vs 2.4; P = 0.0002). Caesarean section was more common after AC-FET (42.7% vs 20.2%; P = 0.003). Other reproductive, obstetric, and perinatal outcomes did not differ significantly between groups. The sample size was powered to detect a difference in CPR with foetal heartbeat, not for comparing live birth rates or obstetric outcomes. The study was performed in ovulatory women undergoing FET, and therefore, results may not be applicable to other populations. This RCT demonstrates no significant difference in CPR with foetal heartbeat in NC-FET and AC-FET in ovulatory women. Given recent data suggesting higher obstetric risks with AC-FET, NC-FET may be preferred in women with normal ovulatory cycles. The study was an investigator-initiated study supported by internal KU Leuven funding (Project number C14/18/106 and C14/24/152) and funding from the Research Foundation Flanders (G.084515N and G.0B1819N to J.V.). K.P. has received grants from Ferring. C.B. has received speaker fees from Gedeon Richter, paid to her institution; travel support from Gedeon Richter, Ferring Pharmaceuticals, and Intuitive; and holds a leadership role as Senior Deputy of the ESHRE SIG Endometriosis and Endometrial Disorders. C.T. has received grants from Merck SA, paid to her institution; consulting fees and speaker fees from Gedeon Richter; travel support from Ferring and Gedeon Richter; and holds leadership roles as Deputy Editor of JNIG and as a board member. A.V. has received speaker fees from Gedeon Richter, paid to his institution, and holds a leadership role as Senior Deputy of the ESHRE SIG Endometriosis and Endometrial Disorders. The other authors declare that there is no conflict of interest to disclose with respect to the content of this article. This trial has been registered at ClinicalTrials.gov (NCT03642665). 17 July 2018. 27 October 2018.

To evaluate whether the timing of luteal phase support (LPS) initiation affects pregnancy outcomes in natural cycle vitrified-warmed blastocyst transfer (NC-FET) cycles. This retrospective cohort study included NC-FET cycles performed between January 2022 and December 2024 at a tertiary university fertility center. Only true natural cycles with blastocyst transfer were analyzed. Patients were divided into two groups according to the initiation of LPS: two days before embryo transfer (Group 1) or on the day of embryo transfer (Group 2). All patients received vaginal and subcutaneous progesterone for LPS. Baseline characteristics, embryo features, serum progesterone levels on transfer day, and reproductive outcomes were compared. Multivariate logistic regression and receiver operating characteristic (ROC) analyses were performed to identify factors associated with clinical pregnancy. A total of 246 NC-FET cycles were analyzed (Group 1: n = 172; Group 2: n = 74). Baseline characteristics, embryo quality, and transfer parameters were comparable between groups. Serum progesterone levels on the day of transfer were significantly higher in Group 1 (32.1 ± 13.0 ng/mL) compared with Group 2 (10.3 ± 3.8 ng/mL; p = 0.001). However, total pregnancy rate (66.2% vs. 47.1%, p = 0.006), clinical pregnancy rate (56.8% vs. 40.7%, p = 0.020), and live birth rate (52.7% vs. 37.2%, p = 0.024) were significantly higher in Group 2. Logistic regression analysis showed that initiation of LPS on the day of transfer was independently associated with increased clinical pregnancy (OR 2.37, 95% CI 1.17-4.81). Serum progesterone level did not predict pregnancy outcomes. In NC-FET cycles, initiating luteal phase support on the day of embryo transfer is associated with improved pregnancy and live birth rates compared with earlier initiation, despite lower serum progesterone levels.

To investigate the association between oral and vaginal probiotic use and pregnancy outcomes in women with infertility. MEDLINE, EMBASE, Emcare, Web of Science, Scopus, and ClinicalTrials.gov were searched from database inception to December 28, 2025. Randomized controlled trials or observational studies that evaluated the use of probiotic administration compared with either a control group or standard care in women with infertility were eligible for inclusion. Study eligibility, data extraction, risk of bias (Cochrane Risk of Bias tool and Risk of Bias in Non-Randomized Studies-of Interventionstool), and certainty of evidence (GRADE [Grading of Recommendations Assessment, Development and Evaluation]) were conducted independently by two authors. The primary outcomes were biochemical and clinical pregnancy rate, live-birth rate, and miscarriage rate among clinical pregnancies and preterm birth. A meta-analysis was performed, and the results were reported as risk ratios (RRs) with 95% CIs. A total of 16 studies including 2,339 women met the eligibility criteria for the meta-analysis. Among women with infertility, oral probiotic supplementation was associated with higher biochemical pregnancy rates (RR 1.27, 95% CI, 1.01-1.60), higher clinical pregnancy rates (RR 1.71, 95% CI, 1.01-2.91), and higher live-birth rates (RR 1.24, 95% CI, 1.01-1.51). Vaginal probiotics were associated with a reduced risk of miscarriage only (RR 0.57, 95% CI, 0.38-0.84). There was a modest association between oral probiotic supplementation and early and clinical pregnancy rates and vaginal probiotics and the reduction of miscarriage; however, the quality of evidence was low to very low. PROSPERO, CRD42025626181.

Embryo Euploidy Rates and Reproductive Outcomes Following Ethanol Sclerotherapy, Laparoscopic Cystectomy, or No Intervention for Ovarian Endometriomas Prior to IVF with PGT-A: A Retrospective Cohort Study.