Human Reproduction

BackgroundPolygenic embryo screening (PES) has recently become available to in-vitro fertilization (IVF) patients, allowing them to evaluate the genetic risk of each of their embryos for polygenic conditions such as heart attack or diabetes. Initial modeling predicted that transferring the embryo with the lowest genetic risk for one or more diseases would substantially reduce prevalence in the next generation, with relative risk reductions up to 50%. However, these models assumed the availability of a prespecified number of embryos and that the embryo with the most favorable polygenic risk is born once transferred to the uterus. In reality, a large percentage of embryo transfers do not lead to live births, and IVF frequently results in no or only a single live birth. MethodsTo quantify the expected risk reduction in the context of IVF, we used two datasets: 6944 ovarian stimulation cycles from 4452 Italian infertility patients and 2138 stimulation cycles of egg donors. In both datasets, we simulated the hypothetical application of PES in these cycles by assigning patients and their embryos randomly drawn polygenic risk scores for a given disease, assuming that embryos have been transferred in increasing order of their risk, and tracing their birth outcomes. We then compared the risk of the embryo born after hypothetical PES to the risk of an embryo born without PES. We either considered only completed cycles or integrated over possible birth outcomes of non-transferred embryos in incomplete cycles. ResultsIn stimulation cycles in infertility patients in which all embryos have been transferred and at least one child was born, we estimate that PES will result in relative risk reductions of just {approx}1-3%. In an intention-to-screen analysis of all completed cycles (regardless of birth outcomes), relative risk reductions are under 0.5%. The risk reductions increase, as expected, with more euploid blastocysts and with younger maternal age. Including incomplete cycles (in which not all embryos have been transferred) increases risk reductions to {approx}2-5%, due to the availability of more euploid blastocysts and a higher live birth rate per transfer in these cycles. Pooling all embryos from all cycles of the same patient increases risk reductions to {approx}5-10%. Relative risk reductions in egg donor cycles reach {approx}20% even with a single stimulation cycle per donor. ConclusionsWith the exception of particularly good-prognosis patients or cycles, typical infertility patients would benefit little from PES. In fertile patients, as represented by egg donors, PES is predicted to achieve greater relative risk reductions. However, even though these reductions are still substantially lower than prior estimates that did not account for realistic live birth rates. Ethical, social, and clinical issues associated with offering PES in the general population should be prioritized in future research.

STUDY QUESTION[Do structural genomic variants, that can be identified by using optical genome mapping, contribute to male infertility?] SUMMARY ANSWER[By using optical genome mapping we can identify several types of structural variants, both known and new, that may contribute to male infertility.] WHAT IS KNOWN ALREADY[Traditional approaches such as karyotyping, CFTR and chromosome Y microdeletion testing are successful in explaining clinical findings in [~]30% of MI patients, leaving the rest without a genetic diagnosis. Recent research suggests at least 265 genes may play a role in male fertility. While the assessment of the roles of copy number variants and single nucleotide variants in monogenic forms of disease in these genes is underway, much less is known about structural variants.] STUDY DESIGN, SIZE, DURATION[We performed a longitudinal case/control study on a total of 220 individuals; 88 patients with male infertility, negative for cytogenetic abnormalities using karyotyping, and molecular testing for chrY microdeletions, and CFTR gene variants, and 132 healthy male individuals that underwent optical genomic mapping for other reasons. Exclusion criteria for the control cohort were low-sperm quality and/or inclusion in IVF procedures. The study was approved by the National Medical Ethics Committee of the Republic of Slovenia (reference number: 0120-213/2022/6). Optical genome mapping was performed from an aliquot of whole blood collected for routine testing purposes at the Clinical Institute of Genomic Medicine (CIGM), UMC Ljubljana from January 2023 to November 2024.] PARTICIPANTS/MATERIALS, SETTING, METHODS[We examined structural variants in 220 participants by using optical genome mapping, which was performed with DLE-1 SP-G2 chemistry and the Saphyr instrument. The de novo assembly and Variant Annotation Pipeline were executed on Bionano Solve3.7_20221013_25 while reporting and direct visualization of structural variants was done on Bionano Access 1.7.2. All obtained variants were filtered using the Bionano Access software and in-house generated gene/regions of interest panel bed files. The first filter was applied to include variants below a population frequency of 10%, and overlapping the regions of interest. Subsequently, all variants occurring with frequency 0% in the internal manufacturer variant dataset were manually evaluated for possible involvement of the overlapping genes or regions in biological processes involved in MI. The male infertility cohort also underwent research whole exome analyses as previously reported. All results of optical genomic mapping were confirmed by an appropriate alternative method where available.] MAIN RESULTS AND THE ROLE OF CHANCE[We show that the overall number of structural variants in MI patients does not differ from that of healthy individuals. By looking in detail at genes and regions associated with MI, we identified 21 rare variants absent from controls in 25.0 % of MI patients, of which five were likely causative, and two would be missed by using traditional approaches. These variants include inversions, duplications, amplifications, deletions (e.g. SPAG1), and insertions/expansions (e.g. DMPK), that were validated using additional methods. While the remaining SV cannot be currently classified as pathogenic according to existing criteria, they open a new avenue in genetic research of MI. LARGE SCALE DATA[Variants reported in this study were deposited into ClinVar under accession numbers SUB15650956 (https://www.ncbi.nlm.nih.gov/clinvar/)] LIMITATIONS, REASONS FOR CAUTION[Technical limitations of optical genome mapping include the lack of DLE-1 labelling of centromeric and telomeric regions, the inability to detect Robertsonian translocations, the unclear exact location of smaller structural variants located between the DLE-1 labels, and unclear boundaries in case of their location in segmentally duplicated regions (this limitation is shared with other methods). The ACGM criteria of rarity are also hard to apply, as the fertility status of the individuals in healthy population databases such as GnomAD and DGV is unknown. Similarly, gene-associated phenotype and the proposed inheritance model both need to be considered as parts of the ACMG criteria, but for many candidate genes associated with MI, no model of inheritance has yet been proposed.] WIDER IMPLICATIONS OF THE FINDINGS[Currently, with the established diagnostic approaches we are able to resolve [~]30% of male infertility cases, with [~]70% of patients remaining undiagnosed. The significance of our work is in showing that rare structural variants can be identified in MI, by using optical genome mapping, opening new avenues of research of the genetics of this important contributor to human fertility.] STUDY FUNDING/COMPETING INTEREST(S)[All authors declare having no conflict of interest in regard to this research. This work was funded by the Slovenian Research and Innovation Agency (ARIS) Programme grant P3-0326: Gynecology and Reproduction: Genomics for personalized medicine] Lay summaryMale infertility affects about 5% of adult males and has complex causes, including genetic ones, such as mutations in the CFTR gene, small deletions on chromosome Y, and balanced translocations, but currently we can only find a genetic cause in [~]30% of patients. This means [~]70% of cases remain undiagnosed but potentially, they too may have a yet unknown genetic cause. Indeed, so far research has shown at least 265 genes have been proposed to play a role in male fertility. In these genes, there has so far been limited research of single nucleotide variants and of copy number variants, but many structural variants are not visible using commonly used methods in clinical genetic testing. Therefore, apart from chromosome Y microdeletions and chromosomal numerical and structural anomalies, such as balanced translocations, the role of smaller structural variants in male infertility is unknown, but based from what we know from other diseases, they also may play a role in male infertility. Optical genome mapping is a novel method for the detection of structural variants, such as balanced and unbalanced translocations, insertions, duplications, deletions, and complex structural rearrangements in a wide range of sizes. By using optical genome mapping to test a cohort of 88 infertile men and 132 healthy controls, we aimed to provide the first insights into the range of SV that may be associated with MI. We found, by using optical genome mapping, the overall number of structural variants in MI patients not to be significantly different to the control group. However, by looking at genes and regions associated with MI, we can find rare structural variants that are absent from controls in 25.0% of MI patients. These variants include inversions, duplications, amplifications, deletions (e.g. deletion in SPAG1), and insertions/expansions (e.g. in DMPK), that were validated using additional methods. Five of these variants (5.6%) were likely causative, and two would be missed by traditional approaches. While the remaining SV cannot be currently classified as pathogenic according to existing criteria, they open a new avenue in genetic research of MI.

Background: Male factor infertility is present in around 40% of couples utilising assisted reproductive technology (ART). However, it is unclear how specific causes of male infertility impact the chance of successful ART treatment, with most research either treating male infertility as single diagnostic group or being isolated smaller-scale studies focused on the treatment and outcomes of specific diagnoses. Objective: To study the impact of eleven specific aetiologies of male infertility on the chance of a clinical pregnancy in couples with known causes of male or female infertility following their first ART cycle. Material and methods: Population-based (initiated ART in Australia and New Zealand in 2020- 2022) cohort study assessing the impact of eleven male infertility diagnoses (idiopathic, Klinefelter syndrome, Y chromosome microdeletions, testis damage from cancer, testis damage from other causes, gonadotropin deficiency, congenital absence of the vas deferens/cystic fibrosis (CBAVD), other obstruction disorder, erectile dysfunction, and ejaculatory disorder) on the chance of a clinical pregnancy following a couple's first complete ART cycle (all fresh and frozen-thawed embryo transfers arising from one episode of ovarian stimulation). Adjusted risk ratios comparing a couples undergoing ART solely for treatment of male infertility with couples undergoing ART solely for treatment of tubal disease were calculated for the chance of a clinical pregnancy following a complete ART cycle and following an attempted fertilisation procedure. Results: A total of 39,053 couples were included, with male infertility present in 42.7% of cases, and the only cause of infertility in just under half of these cases. In more than three-quarters of male infertility cases the cause of infertility was unknown (idiopathic) or undiagnosed. Most couples undertaking ART for treatment of male infertility can expect similar success rates to couples seeking treatment for good prognosis female infertility diagnoses. However, those with Klinefelter syndrome and Y chromosome microdeletions had a 59.5% (aRR: 40.5% [95% CI: 16.9%-64.1%]) and 28.9% (aRR: 71.1% [95% CI: 45.5%-96.7%]) lower chance of a clinical pregnancy per initiated stimulation cycle compared to those with tubal disease as the only source of infertility. However, there was no difference once sperm was retrieved compared to other diagnoses tending to require surgical sperm retrieval, use frozen oocytes and necessitating ICSI. Discussion and Conclusion: In this population-based study most couples undergoing ART because of male infertility had similar success rates to those undergoing ART for treatment of female tubal disease, except for patients with Klinefelter syndrome and Y chromosome microdeletion who had approximately half and three-quarters the chance of a clinical pregnancy due to failed sperm retrieval/survival, but no difference (accounting for the use of surgical sperm, ICSI and potentially frozen oocytes) in outcomes once sperm were available. While these finding are reassuring for most men presenting to an ART clinic with male infertility, with more than three-quarters of male infertility cases reported as being idiopathic, there is an urgent need for greater research on the causes, diagnosis and implications of male infertility.

ObjectiveTo evaluate whether hyaluronan-enriched transfer medium improves live birth rates in biopsied euploid blastocyst transfers and to examine the role of zona pellucida disruption in mediating this effect. DesignRetrospective cohort study. ParticipantsA total of 1,221 single frozen euploid blastocyst transfers performed between January 2011 and December 2024. InterventionEmbryo transfer using hyaluronan-enriched transfer medium compared with standard zwitterionic-buffered transfer medium. All embryos underwent trophectoderm biopsy resulting in zona pellucida disruption. Main Outcome MeasuresLive birth rate. Secondary outcomes included biochemical pregnancy and clinical pregnancy rates. ResultsHyaluronan-enriched transfer medium was associated with significantly higher live birth rates compared with standard medium (59.1% vs. 43.2%; absolute difference 15.9%, 95% confidence interval 10.3%-21.5%; relative risk 1.37, 95% confidence interval 1.22-1.54; P < 0.001). Clinical pregnancy and biochemical pregnancy rates were also significantly higher in the hyaluronan group (P < 0.001 for both comparisons). Sensitivity analysis restricted to first transfers per patient (n = 715) confirmed persistence of the live birth benefit (61.2% vs. 47.1%; absolute difference 14.1%, 95% confidence interval 6.9%-21.3%; relative risk 1.30, 95% confidence interval 1.13-1.49; P < 0.001). Maternal age was comparable between groups. ConclusionUse of hyaluronan-enriched transfer medium is associated with a clinically meaningful increase in live birth rates in biopsied euploid blastocyst transfers. Zona pellucida disruption created during trophectoderm biopsy may facilitate enhanced embryo-endometrial interaction, improving implantation efficiency.

1.Study questionDo singletons conceived by medically assisted reproduction (MAR) experience an elevated incidence of childhood cancers and are they at a greater risk of such cancers compared to naturally-conceived singletons? Summary answerWe found no strong evidence the adjusted risk of childhood cancers is increased for MAR-conceived singletons. What is known alreadyThere is longstanding concern children conceived via MAR may be at increased risk of childhood cancer. Current epidemiological evidence does not support such a relationship. Study design, size, durationWe conducted a retrospective population-based cohort study of 5,104,121 singletons born in Australia between 1991 and 2019. Median follow-up time varied from 4 to 10 years depending on mode of conception. Participants/materials, setting, methodsWe linked birth records to public medical insurance data of the mother to ascertain MAR conception. We classified treatment as ovulation induction/intrauterine insemination (OI/IUI) or assisted reproductive technology (ART; IVF/ICSI), with ART coded as either fresh embryo transfer or frozen embryo transfer. The cohort included 4,924,354 naturally-conceived singletons and 179,767 singletons conceived via MAR. We calculated standardised incidence ratios (SIRs) to ascertain differences in population incidence of childhood cancer, and generated hazard ratios (HRs) using flexible parametric survival models controlling for key confounders. We report absolute incidence and risk differences for both statistical approaches. Main results and the role of chanceThere was no increase in the incidence or risk of all childhood cancers combined for singletons conceived via MAR, either any MAR or specific MAR types. There was some evidence the incidence of leukemias, myeloproliferative diseases, and myelodysplastic diseases was increased after ART compared to the general population (SIR: 1.32, 95% CI 1.02-1.68; equating to 2.09, 95% CI 0.13-4.44 extra cancers per 100,000 person-years), but no increased risk after adjusting for available confounders (HR: 1.04, 95% CI 0.73-1.46). These cancers showed increased incidence and risk for those conceived via IVF (SIR: 1.54, 95% CI 1.01-2.26; HR: 1.77, 95% CI 1.06-2.95), but not ICSI (SIR: 1.27, 95% CI 0.83-1.85; HR: 0.76, 95% CI 0.48-1.22). Incidence of renal tumours was elevated after IVF (SIR: 2.37, 95% CI 1.02-4.67; equating to 1.83, 95% CI 0.03-3.99 extra cancers per 100,000 person-years) and frozen transfer ART (SIR: 2.52, 95% CI 1.09-4.97; equating to 2.12, 95%CI 0.12-5.53 extra cancers per 100,000 person-years), however risk was not elevated after adjusting for available confounders (HR: 1.06, 95% CI 0.47-2.38; and HR: 1.63, 95% CI 0.73-3.61 respectively). Limitations, reasons for cautionWe did not have information on parental cause of infertility, which could be a confounder for childhood cancer, although we did adjust for parental history of cancer. For many specific cancer types, fewer than 50 cases were observed in total. Given the number of comparisons reported and closeness of the lower-bound confidence interval to 1, we cannot exclude that a significant association between conception via IVF and leukemias, myeloproliferative diseases, and myelodysplastic diseases reflects a type I error. Wider implications of the findingsOur findings align generally with published meta-analyses on the risk of childhood cancers following MAR conception and reinforce the need for very large studies to increase confidence. Parents who have conceived via MAR and their offspring can be reassured there is not strong evidence the treatments increase the overall incidence or risk of childhood cancer. Study funding/competing interest(s)This work was funded by the National Health and Medical Research Council (NHMRC: APP1164852). Dr ARW declares that their involvement in this work was supported by employment at UNSW Sydney. Prof CMV declares payment to their institution from the National Health and Medical Research Council (APP1164852). Prof NH declares payment to their institution from the National Health and Medical Research Council (APP1164852); royalties and licenses for Berek and Hackets Gynecologic Oncology (Walters Kluwer); royalties and licenses for Hacker and Moores Essentials of Obstetrics and Gynecology (Elsevier); consulting fees from Darwin Hospital and Gold Coast University Hospital; support for attending the British Gynaecological Cancer Society meeting in Aberdeen, UK, Jun 2023; support for attending the Symposium on Gynaecological Cancer in Budapest, Hungary, Nov 2023; support for attending the International conference of the Rajiv Gandhi Cancer Centre in Delhi, India, Mar 2025; and membership of the Medical Advisory Committee for TruScreen (Australia and New Zealand). A/Prof SO declares that they received payment to their institution from the National Health and Medical Research Council (APP1164852); they received a grant from the European Society for Human Reproduction and Embryology (Open call 2022) including payment to their institution; and that they are a member of the Advisory Board of the Cervical Screening Program in Norway through The Norwegian Institute of Public Health (NIPH), for which they were reimbursed travel expenses to their institution. Prof MC declares support for Theramex European Society for Human Reproduction and Embryology registration and Fertility Society of Australia and New Zealand registration and accommodation. A/Prof USD declares that her involvement in this work was supported via an Early Career Fellowship from the Cancer Institute NSW (ID: 2020/ECF1163) and employment at UNSW Sydney. A/Prof USD also declares payment to their institution from the National Health and Medical Research Council (APP2035240) and the Medical Research Future Fund (APP2032214; APP2038377), and the Australian Research Council (DP240100072) as well as current grants from NSW Health, Prince of Wales Hospital Foundation, and unpaid involvement as an Associate Editor for the "Journal of Psycho-Oncology Research and Practice". Prof LJ declares payment to their institution from the National Health and Medical Research Council (APP1164852). Prof RJN declares they are the Chair of the Clinical Advisory Committee, Westmead Fertility; External mentor at VinMec hospital; Editorial Editor at the journal "Fertility and Sterility"; and has received funding from the National Health and Medical Research Council (NHMRC) for the NHMRC Centre for Research Excellence in Womens Health in Reproductive Life (CRE WHiRL). A/Prof CS declares stock or stock options associated with CSL Ltd, Sigma Healthcare Ltd, Resmed Inc, Medical Developments International Ltd, Vitrafy Life Sciences Ltd, Intuitive Surgical, and Steris PLC. Prof GMC declares payment to their institution from the National Health and Medical Research Council (APP1164852). Prof CV declares payment to their institution from the National Health and Medical Research Council (APP1164852); research grants receive from Merck KGaA and Ferring; payments for honoraria from Merk Ltd, Merk Sharpe & Dohme, Ferring, Organon, Gedeon-Richter for being an invited lecturer in scientific meetings/conferences on multiple occasions as well as member of advisory boards for these companies who have a commercial portfolio in the field of assisted reproduction technology (ART); and speaking fees from IBSA, Vianex, Sonapharm; travel support for their participation in scientific meetings/conferences both nationally and internationally, usually as an invited speaker for the following companies - Merck Ltd, Merck Sharpe & Dohme, Ferring, Organon, Gedeon-Richter; unpaid involvement as a Board member of the Hellenic Society of Fertility and Sterility, Member of the Editorial Board of the journal "Human Reproduction", Senior Deputy of the Coordination Committee of the Special Interest Group "Reproductive Endocrinology" of the European Society for Human Reproduction and Embryology, Member of the Editorial Board of the journal "F&S Reviews", Member of the Editorial Board of the journal "RBM Online", Member of the Editorial Board of the journal "Reproductive Biology & Endocrinology", Member of the Editorial Board of the journal "Frontiers in Endocrinology", and Member of the Editorial Board of the journal "Reproductive Sciences". SubjectReproductive epidemiology

Background Endometriosis is associated with adverse pregnancy outcomes in standard observational studies, including placental complications, preterm birth, and caesarean delivery. However, causal inference from these studies is complicated by residual confounding, differential clinical management, and the presence of intermediate factors such as subfertility and the use of assisted reproductive technologies, which may lie on the causal pathway between endometriosis and adverse outcomes. We applied Mendelian randomization (MR) to estimate the causal effects of genetic liability to endometriosis on a broad range of maternal and perinatal outcomes. Methods We conducted a two-sample MR study using summary-level GWAS data. Forty-one independent genetic instruments for endometriosis were derived from the largest available GWAS meta-analysis (60,674 cases; 701,926 controls; mean F-statistic = 279). SNP-outcome associations were obtained for 30 outcomes from the MR-PREG collaboration, FinnGen Release 12, and a postpartum haemorrhage GWAS meta-analysis, spanning placental disorders, pregnancy timing, labour and delivery, hypertensive disorders, fetal growth, and neonatal outcomes. Primary analyses used the inverse-variance weighted method, complemented by MR-Egger, weighted median, weighted mode, and MR-PRESSO. Trio-based models disentangled maternal from fetal genetic contributions. Multiple testing was addressed using false discovery rate correction. Findings Across 30 outcomes, only placenta praevia reached FDR-corrected significance, with a robust and consistent causal signal across four of five sensitivity methods (IVW OR 1.62, 95% CI 1.33-1.97; q<0.001). Within the placental disorders domain, estimates for premature placental separation and the broader placental disorders phenotype were directionally concordant but imprecise. For premature rupture of membranes, estimates were concordant across three methods, though the association was sensitive to cohort exclusion and did not survive multiple testing correction and should be interpreted cautiously. By contrast, hypertensive disorders, gestational diabetes, postpartum haemorrhage, stillbirth, and most neonatal outcomes showed estimates consistently close to the null across all methods. Trio-based analyses suggested predominantly maternal genetic pathways for most outcomes; fetal genetic contributions were not significant after correction for multiple testing, with exploratory signals observed for birthweight-related outcomes requiring independent replication. Interpretation A robust causal signal for placenta praevia alongside directionally consistent estimates across the placental disorders domain, suggests that mechanisms related to abnormal implantation and placentation may constitute a major mechanism for how endometriosis liability influences pregnancy. These results suggest that previously reported associations with broader obstetric outcomes may partly reflect confounding or clinical management patterns, and support targeted surveillance for abnormal placentation rather than a generalised elevation of obstetric risk.

ObjectivesGiven the widespread use of period-tracking applications and evidence that some users rely on fertile-window predictions for pregnancy prevention, we aimed to quantify pregnancy risk arising from misclassification of biologically fertile days by period-tracking applications, and to compare this risk across calendar-based and basal body temperature (BBT)-supported period tracking and a digital contraceptive regulated as a medical device. MethodsWe conducted an observational analysis of cycles of mobile fertility application users who logged urinary luteinizing hormone (LH) tests. Biologically fertile days were defined using an LH-based reference fertile window (days -5 to 0 relative to ovulation). Three approaches were evaluated: a calendar-based period tracking application, a BBT-supported period tracking application, and a FDA-cleared digital contraceptive. Outcomes included day-specific frequency of fertile days misclassified as safe, cycle-level misclassification, and predicted pregnancy risk per cycle. Analyses were repeated in a subgroup of irregular cycles. Results543,167 menstrual cycles with a clear LH surge signature were included in the analysis. Calendar-based period tracking frequently misclassified fertile days as safe, with 67% of cycles containing at least one at-risk day and 25% containing at least one high-risk day. The mean predicted pregnancy risk per cycle was 22%, increasing to 65% in irregular cycles. BBT-supported period tracking reduced misclassification but remained associated with substantial risk (41% of cycles with at least one at-risk day; mean predicted pregnancy risk 9%). In contrast, the digital contraceptive showed consistently low misclassification (3% of cycles with any at-risk day and a mean predicted pregnancy risk of 0.5%). ConclusionsBoth calendar-based and BBT-supported period-tracking applications not intended for contraception frequently misclassify biologically fertile days and should not be considered reliable tools for pregnancy prevention. Regulated digital contraceptives demonstrate substantially lower pregnancy risk. Short condensationPeriod-tracking apps frequently misclassify fertile days as safe, including days with high pregnancy risk. In a large real-world analysis, both calendar- and BBT-supported trackers showed substantial risk, unlike digital contraception methods regulated as a medical device.

Cannabis (marijuana) is the most widely used recreational drug in the USA accounting for about 62 million users in 2024. Among cannabis users, 26% are of prime reproductive age (18-25 years). Delta-9 tetrahydrocannabinol (THC) is the principal psychoactive component of cannabis and has been detected in human seminal fluids. Although abundant evidence indicates adverse effects of THC exposure on spermatogenesis in different species, acute effects of THC on postejaculatory sperm including fertilization potential and subsequent carryover effects on embryo development are largely unknown. The present study was designed to provide missing information on structural and mechanistic effects of THC exposure to postejaculatory sperm function by evaluating sperm indices often overlooked or masked during clinical evaluation. A bovine embryo continuum model was employed to determine effects of THC on sperm structure, kinematics, bioenergetics, and binding mechanisms. Effects of THC on the sperm genomic and epigenomic landscape were determined, complemented by paternal carry over effects on embryo development as a human translational model to elucidate paternal effects on future development, and to mirror sperm exposure during transport within the female reproductive tract. Cryopreserved bovine sperm from three bulls were independently exposed to physiologically relevant concentrations of THC (0 and 32nM, n = 2 individual replicates/bull) for 24 h under non-capacitating conditions at 25{degrees}C followed by quantification of sperm kinematics at 37{degrees}C. Samples of THC-exposed sperm and vehicle-control (0.1% DMSO) were collected in replicate following immediate addition of THC (0 h) and again at 24 h. DNA damage, acrosome integrity, bioenergetics, changes to DNA methylation and embryo development were quantified. Data were analyzed by logistic regression with a generalized linear mixed effect model. Computer-assisted sperm assessment revealed a reduction in progressive motility of THC-exposed sperm after 24 h while other parameters were not affected. Acrosome integrity as determined by flowcytometric analysis with FITC-PSA was severely compromised in THC-exposed sperm (P [&le;] 0.05), despite no detectable difference in capacitation status using merocyanine staining. Similarly, DNA integrity as determined by TUNEL assay was significantly impaired after 24 h of THC exposure (P [&le;] 0.05). Mechanistic effects of THC were explored through characterization of the transmembrane G-protein coupled cannabinoid 1 receptor (CB1). CB1 is expressed in the post-acrosomal region and its abundance decreased as compared to unexposed sperm. Alterations to the methylation landscape of sperm were then determined after 24 h of THC exposure through whole-genome Enzymatic Methyl Sequencing. PCA analysis indicated that sperm from different males formed distinct clusters, implying individual differences among bulls, while the effects of THC exposure produced tighter clusters. Paternal carryover effects on embryos derived by in vitro fertilization from THC exposed sperm had reduced 2-cell cleavage, 8-16 cell morula development, and reduced blastocyst development compared to unexposed sperm (46% vs. 33%). In conclusion, post-ejaculatory mammalian sperm exposure to THC compromises acrosome integrity, induces DNA damage, changes the sperm methylome, and reduces developmental potential. Collectively, these data implicate new considerations for recreational and clinical use of cannabis that impact cellular and molecular mechanisms important for sperm function with detrimental consequences for gamete interaction and embryo development.

STUDY QUESTIONAre pathogenic variants in Homeodomain-interacting protein kinase (HIPK4) associated with sperm head abnormalities causing male infertility? SUMMARY ANSWERHIPK4 is a novel candidate gene associated with sperm head defects and human male infertility. WHAT IS KNOWN ALREADYNumerous genes causing male infertility due to Multiple Morphological Abnormalities of the sperm flagella (MMAF) have been described but the genetic basis of sperm head defects is less well understood. STUDY DESIGN, SIZE, DURATIONFour infertile brothers displaying varying degrees of quantitatively and/or qualitatively impaired spermatogenesis, their parents, and their fertile brother were included in the study. Further, the Male Reproductive Genomics (MERGE) cohort comprising exome/genome sequencing data of >3,300 men was queried. PARTICIPANTS/MATERIALS, SETTING, METHODSWe performed exome sequencing in all five brothers and their parents. To characterise the sperm phenotype, standard semen analysis, immunofluorescence staining, and transmission-electron microscopy (TEM) were carried out. Further, we evaluated the impact of the HIPK4 variant in cell culture experiments using HEK293T cells. MAIN RESULTS AND THE ROLE OF CHANCEAnalysing the exome data, we could not identify a common genetic cause in all four affected brothers. However, one of the affected brothers was compound heterozygous for two loss-of-function variants in DNAH17 (c.1076_1077dup p.(Lys360*) and c.7752+2T>A p.?) associated with markedly reduced sperm motility and MMAF. The variants pathogenicity was further validated by TEM of flagellar cross-sections revealing an outer dynein arm defect and axonemal disruption. On the contrary, his three infertile brothers were homozygous for the start-loss variant c.1A>G in HIPK4. This gene is expressed during spermiogenesis and is reportedly involved in sperm head shaping in mice. Heterologous expression of (partial) HIPK4 variant cDNA elucidated the alternative use of an in frame start codon located 35 amino acids downstream, resulting in an N-terminally truncated protein p.(Met1_Glu35del). The truncated HIPK4 protein lacks parts of its kinase domain and shows reduced protein stability. In line with published mouse models, all three brothers displayed 100% abnormal sperm head morphology with variable defects. Importantly, one brother affected by HIPK4 variants fathered a child after successful intracytoplasmic sperm injection demonstrating that it is a treatment option for HIPK4-related teratozoospermia. No further men from the MERGE cohort were affected by biallelic HIPK4 variants. Taken together, HIPK4 is an autosomal-recessive candidate gene associated with sperm head defects and male infertility. LARGE SCALE DATAThe reported variants in DNAH17 and HIPK4 were submitted to ClinVar. LIMITATIONS, REASONS FOR CAUTIONIndependent replication is required to assess the phenotypic spectrum and the reproductive outcome associated with biallelic HIPK4 variants and to formally establish the gene-disease relationship for male infertility. WIDER IMPLICATIONS OF THE FINDINGSThis study raises awareness of the significant genetic heterogeneity of male infertility. The described family highlights that distinct genetic causes may underlie a seemingly similar phenotype. Exome sequencing of families is helpful to efficiently disentangle individual causes among affected family members. STUDY FUNDING/COMPETING INTEREST(S)N.N., J.R., H.O., S.L., C.F., and F.T. were supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) within the Clinical Research Unit Male Germ Cells (CRU326, project number 329621271). R.T.W., N.N., J.R., H.O., and F.T. were supported by the Federal Ministry of Research, Technology and Space (BMFTR) as part of the project ReproTrack.MS (grant 01GR2303). S.A.K. was supported by the DFG Clinician Scientist programme CareerS Munster (project number 493624047). A.S.G. was supported by the Medical Faculty Munster via an Innovative Medical Research (IMF) grant (GA-122104).

Introduction The aim of this study was to determine the annual age- and sex-specific prevalence of gender-affirming hormone and puberty blocker use among young people with a gender incongruence (GI) diagnosis in Norway. Methods We integrated data from multiple Norwegian national registers to perform a nationwide register-based study of individuals with known sex assigned at birth who were born in the period 1975-2017 and resident in Norway for all or part of the period 2008-2022. We first calculated the annual age- and sex-specific incidence of GI diagnoses in the population. Then, we calculated the annual age- and sex-specific prevalence of androgen, estrogen, and puberty blocker use among individuals with a GI diagnosis who were under age 25 (for androgens and estrogens) or 18 (for puberty blockers) in the year that they collected the prescription. Results The incidence of GI diagnoses has increased among youth in Norway, most notably since 2015 and with the largest increase among teens assigned female at birth. The prevalence of feminizing and masculinizing hormone therapy has increased in this period as well, but mainly among the oldest teens and young adults. The prevalence of puberty suppression is mostly low but has also increased since 2015, especially in recent years among teens assigned male at birth. Conclusion The prevalence of gender-affirming hormone and puberty blocker use has increased among transgender youth in Norway, concurrently with an increase in the incidence of GI diagnoses.

IntroductionNon-obstructive azoospermia (NOA) represents the most severe form of male infertility. Current clinical tools have limited ability to predict sperm production or guide surgical sperm retrieval. Conventional B-mode ultrasound provides qualitative grayscale images and cannot characterize testicular microstructure relevant to spermatogenesis. Quantitative ultrasound (QUS) provides objective parameters from raw radiofrequency data, which quantitatively measure tissue heterogeneity. We hypothesize that men with spermatogenesis will have different QUS features compared to men without spermatogenesis (measured by total motile count, TMC, on semen analysis), with the goal of identifying imaging biomarkers for prognosis and intraoperative guidance. MethodsWe prospectively analyzed men presenting for infertility evaluation who underwent high-frequency ultrasound imaging and semen analysis. Imaging was performed using a 36-MHz transducer with fixed acquisition parameters. Ninety-two QUS features were extracted from manually annotated testicular regions of interest, including Nakagami distribution parameters (m, {omega}, k), envelope statistics, and texture features. Univariate associations between each QUS feature and TMC were assessed using Spearman correlation with Bonferroni correction. Top-performing features were evaluated using logistic regression and receiver operating characteristic (ROC) analysis to discriminate sperm presence or absence (TMC>0 vs TMC=0). ResultsThirty-seven men (18 azoospermic, 19 with sperm present in the ejaculate) contributed 135 regions of interest. Seventeen of 92 QUS features significantly correlated with TMC after correction. The coefficient of variation of the Nakagami k-factor within the superficial testicular parenchyma (K_Zone1_Cv) demonstrated the strongest correlation ({rho}=0.51, corrected p<0.001), suggesting that greater spatial heterogeneity in the superficial parenchyma was associated with higher sperm counts. K_Zone1_Cv discriminated sperm presence with an AUC of 0.77 (95% CI 0.60-0.92), sensitivity 73.7%, and specificity 83.3%. QUS features with the highest univariate association were highly intercorrelated, suggesting a shared biological signal. ConclusionQuantitative ultrasound-derived measures of testicular microstructure heterogeneity correlate with sperm production and demonstrate moderate discrimination of sperm presence. These findings suggest QUS may provide a non-invasive imaging biomarker of spermatogenesis. Study findings warrant further assessment and validation in male infertility for sperm retrieval prognosis and the potential for intra-operative surgical guidance.

Polycystic ovary syndrome (PCOS) is a heterogenous reproductive disorder that is often associated with metabolic dysfunction, as well as comorbidities such as pregnancy complications. Although metabolic traits like hyperinsulinemia (i.e., elevated insulin without hypoglycemia) likely exacerbate the reproductive and metabolic features of PCOS, the precise impacts of specific metabolic traits on PCOS pathogenesis, symptom severity, and comorbidity incidence are not known. The aim of our study was to investigate the relationships between insulin levels, PCOS-like traits, and pregnancy complications by limiting endogenous insulin production in a mouse model of PCOS. Using Ins1-null mice with modulated Ins2 gene dosage (Ins1-/-:Ins2+/- versus Ins1-/-:Ins2+/+ littermates), we longitudinally assessed metabolic and reproductive phenotypes in PCOS-like mice generated via prenatal anti-Mullerian hormone (PAMH) exposure. We observed mild reproductive characteristics of PCOS in PAMH mice of both genotypes, including increased anogenital distances, delayed puberty, and disrupted estrous cycling, but did not detect robust PAMH-induced metabolic changes across six months. In the absence of PAMH-aggravated metabolic dysfunction or hyperinsulinemia--even in mice fed a high-fat, high-sucrose diet--reducing Ins2 gene dosage did not notably change most measured traits. However, high-fat, high-sucrose-fed PAMH pregnant dams exhibited a diminished pregnancy-induced insulinogenic response and a trend for reduced {beta}-cell mass compared to control mice, together with superior blood glucose homeostasis despite the physiological challenges of pregnancy. Therefore, while Ins1-null PAMH mice did not manifest pronounced PCOS-like metabolic features, prenatal AMH exposure can cause shifts in metabolic homeostasis during pregnancy.

BackgroundMitochondrial dysfunction is a leading contributor to the decline in oocyte quality associated with maternal aging. Prior investigations of mitochondrial function in the ovarian follicle have largely treated the mitochondrial pool as a homogeneous population, reporting aggregate values that may obscure biologically meaningful differences between distinct mitochondrial subpopulations. The present study addresses this limitation by characterizing mitochondrial subpopulation dynamics in oocytes and cumulus granulosa cells at single-organelle resolution using fluorescence-activated mitochondria sorting (FAMS). ResultsAnalysis of the aggregate mitochondrial population in mouse oocytes revealed no significant age-associated differences in mitochondrial DNA copy number or membrane potential, a result that would previously have been interpreted as evidence of minimal age-related mitochondrial change. Subpopulation analysis revealed this conclusion to be incomplete: aged oocytes showed significantly elevated mitochondrial DNA copy number specifically within the high membrane potential and small mitochondrial subpopulations, with no significant differences in the low membrane potential or large subpopulations. NMN supplementation normalized mitochondrial DNA copy number in the high membrane potential and small subpopulations toward young levels while producing an opposing effect in large mitochondria, demonstrating subpopulation-specific rather than uniform rejuvenation. In cumulus cells, significant age-associated changes were detectable at the aggregate level, including a reduction in mitochondrial DNA copy number and an elevation in membrane potential, and subpopulation analysis further resolved these findings. The age-associated reduction in cumulus cell mitochondrial DNA copy number was driven predominantly by the high membrane potential subpopulation. NMN supplementation exerted opposing effects on small and large cumulus cell mitochondrial subpopulations, increasing mitochondrial DNA copy number above both young and aged levels in small mitochondria while further reducing it below aged levels in large mitochondria. ConclusionsViewing the mitochondrial pool as a heterogeneous mixture of functionally distinct subpopulations rather than a uniform population reveals age-associated alterations in oocytes and cumulus cells that are undetectable by aggregate analysis. NMN supplementation exerts subpopulation-specific effects in both cell types, identifying specific mitochondrial subtypes as more precise targets for future mechanistic investigation of age-associated infertility than the mitochondrial pool considered in aggregate.

The human endometrium undergoes cyclic, hormone-driven remodeling that establishes a transient window of receptivity required for embryo implantation, placentation, and maintenance of pregnancy. Decidualization of endometrial stromal cells is a central component of this process and can be induced in vitro using cAMP alone or in combination with ovarian steroid hormones (EPC: estradiol, progesterone, and cAMP). Although cAMP activates the core decidual transcriptional program, whether hormone supplementation induces a more physiologically relevant response remains unclear, particularly in 3D endometrial organoid (Endo-organoid) models which have emerged as a new alternative methodology (NAM). Here, we compared morphological and transcriptomic responses of human endometrial stromal cell-derived Endo-organoids undergoing decidualization induced by cAMP or EPC stimulation. EPC-treated Endo-organoids exhibited enhanced structural remodeling and more advanced morphological transformation compared with cAMP-treated organoids. RNA-seq analysis revealed substantial overlap in canonical decidual gene expression between the two conditions, but EPC induced broader transcriptional and pathway-level changes, including enrichment of metabolic, stress-response, and differentiation-related processes. Together, these findings demonstrate that while cAMP activates the core decidual program, EPC elicits a broader and more physiologically relevant decidualization response in 3D human Endo-organoids, providing guidance for optimizing Endo-organoids to study endometrial receptivity, implantation, and early pregnancy success.

BackgroundApproximately one-third of men having undergone gonadotoxic treatment in their childhood experience impaired testicular function for whom autologous transplantation of cryopreserved immature testicular tissue may represent the only opportunity to restore their fertility. Pre-clinical studies have demonstrated successful restoration of spermatogenesis following grafting of immature testicular tissue in various species, including non-human primates. In 2002, our institution pioneered with clinical testicular tissue banking for fertility preservation in boys and adolescents. Over time, this strategy has been increasingly implemented by numerous fertility centres worldwide for patients at high risk of treatment-induced sterility. Here, we report the first human case of autologous transplantation of frozen-thawed immature testicular tissue. PatientIn 2008, testicular tissue was cryopreserved from a pre-pubertal boy diagnosed with sickle cell disease. The procedure was performed after a three-year hydroxyurea treatment and prior to receiving conditioning therapy with busulfan and cyclophosphamide for haematopoietic stem cell transplantation. One testis was surgically removed, sectioned into small fragments, and cryopreserved. Histological analysis confirmed preserved tubular architecture and the presence of spermatogonia. During the period from 2022 to 2024, the patient consistently presented with azoospermia. In December 2024, at the time of transplantation, two abnormal sperm cells were detected after enzymatic digestion. MethodEleven testicular tissue fragments (4-21 mm3) were thawed and autologously grafted to four intra-testicular and four subcutaneous scrotal sites. Over a one-year follow-up period, graft survival, vascularization, hormone profiles, and semen parameters were monitored. One year after transplantation, all grafts were surgically retrieved. ResultsPost-operative recovery was uneventful. No significant changes in endocrine or semen parameters were observed during follow-up. Whereas the intra-testicular grafts exhibited a compact parenchyma that was distinct from the looser surrounding adult parenchyma and remained readily identifiable as graft tissue, the scrotal grafts appeared more fibrotic. Enzymatic digestion of the grafts was required to recover spermatozoa, with one spermatozoon obtained from one of the four intra-testicular grafts. Histological evaluation revealed intact tubular architecture and maturation of somatic cells across all grafts. Spermatogonial stem cells, together with evidence of active spermatogenesis, were identified in two of the four intra-testicular grafts, whereas no germ cells were detected in the subcutaneous scrotal grafts. ConclusionThese findings demonstrate that human immature testicular tissue can survive long-term cryostorage, revascularize after transplantation and establish spermatogenesis in vivo. This study provides essential proof-of-concept for fertility restoration in individuals who banked testicular tissue before puberty. FundingThis study was supported by the Research Programme of FWO Vlaanderen (Research Foundation-Flanders; G0A6U25N) and VUB strategic research program (SRP89). Trial Registration: NCT05414045

Study questionHow is glycodelin, a glycoprotein secreted by reproductive tissues, causally related to reproductive diseases and traits? Summary answerWe present evidence for a causal role of sex hormones in determining glycodelin levels, but limited evidence that glycodelin subsequently causally impacts reproductive traits. What is known alreadyGlycodelin is expressed in female and male reproductive tissues and has four glycoforms (-A, -C, -F and -S), with the glycosylation pattern determining its function. Differences in the levels of glycodelin are associated with reproductive traits, including fertility, endometriosis, preeclampsia, and female-specific malignancies. Study design, size, durationWe used cross-sectional data from the UK Biobank to investigate relationships between glycodelin and reproductive-related traits in men and women by performing genome-wide association studies (GWAS) and Mendelian randomization (MR) analyses. Participants/materials, setting, methodsWe included individuals of European genetic ancestry aged 40-69 in 2006-2010, with genetic data in the UK Biobank v3 release. We performed GWAS of glycodelin levels in 46,468 people, stratified by sex (21,368 men and 25,100 women) and menopause status (6,409 pre- and 18,691 post-menopausal women). We tested bidirectional casual associations between glycodelin levels and 19 reproductive-related traits using one- and two-sample MR analyses. Main results and the role of chanceNine genetic signals reached genome-wide significance (P<5x10-8) across the glycodelin phenotypes. A known genetic signal (rs9409964) near the PAEP gene, which encodes glycodelin, was most strongly associated (P<3x10-80 across all phenotypes), and had heterogeneous effects (effect (SD) per A allele of 1.31 in men vs 0.60 in women, and 0.4 in pre- vs 0.9 in post-menopausal women). Higher serum concentrations of bioavailable testosterone raised glycodelin in men (effect = 0.14 SD, IVW P=4.1x10-13), while effects in women depended on menopause status (pre-menopausal effect = -0.16 SD, IVW P=3.6x10-3; post-menopausal effect = 0.10 SD, IVW P=5.9x10-4). There was no strong evidence that differences in glycodelin levels were caused by, or were the cause of, other reproductive-related traits. Limitations, reasons for cautionProteomic measurements of glycodelin did not differentiate between glycoforms and were derived from blood and might not reflect levels in reproductive tissues. The sample size for the pre-menopausal GWAS was modest, reducing our power to detect relationships with reproductive conditions. Genetic instruments are assumed to be proxies for average lifelong exposure, which does not reflect variation in hormones and biomarkers over lifetime. Wider implications of the findingsWe suggest that reported associations of glycodelin with reproductive conditions are likely to result from the effects of sex hormones rather than being directly causal. These findings may help reconcile previously conflicting associations between glycodelin and reproductive traits.

Human embryo implantation, occurring approximately one week after fertilization, remains poorly understood due to ethical and technical limitations of in vivo investigation. To overcome these barriers, and model this critical developmental event, encompassing peri- and early post-implantation stages, we used an in vitro embryo attachment model composed of donor-derived endometrial epithelial cells forming an open-faced endometrial layer (OFEL) and human stem cell-derived blastoids recapitulating human day 5 blastocysts in peri-implantation model. Following attachment, developmental progression was further investigated on laminin-coated substrates to capture early post-implantation dynamics. Despite its central role as the primary endocrine signal of early pregnancy, human chorionic gonadotropin (hCG) remains largely uncharacterized in this context. Here, we describe the transcriptomic profile of blastoid-endometrial co-cultures relative to OFEL alone, identifying CGA and CGB3/5/8 as among the most strongly upregulated genes following blastoid attachment to hormonally stimulated OFEL. Consistent with these findings, immunoassays and luteinizing hormone/choriogonadotropin receptor (LHCGR) activation assays of conditioned media confirmed the secretion of heterodimeric, biologically active hCG and its free subunits in co-cultures, but not in endometrial layers alone. Notably, the hyperglycosylated hCG heterodimer was the predominant isoform detected. Co-culture with the endometrial component significantly increased hCG secretion compared with blastoids cultured alone, an effect further enhanced by hormonal priming in the peri-implantation model. Collectively, these findings indicate that a hormonally primed endometrial environment not only promotes blastoid attachment but also amplifies embryonic hCG production and bioactivity, underscoring the importance of maternal endocrine cues in early embryo-endometrium communication. Furthermore, our peri- and early post-implantation models recapitulate key aspects of reciprocal endocrine signaling between embryonic and endometrial tissues, providing a tractable experimental framework to investigate embryo-endometrium crosstalk.

Infertility generates profound psychological and social distress for both women and men, yet mens communicative experiences remain comparatively underexamined. Male infertility (MI) is often shaped by stigma, norms of masculinity, and limited opportunities for emotional disclosure, constraining help-seeking in offline settings. This study investigates how men use anonymous online peer-support spaces to discuss MI by analyzing discussions from the r/maleinfertility subreddit on Reddit. Using natural language processing techniques, we examined 10,769 posts and 80,381 comments published between 2013 and 2025. Analyses assessed sentiment and emotional expression, topic structure, hyperlink networks, and discussions related to diagnostic testing, treatment decision-making, and donor sperm use. Topic modeling revealed a functional differentiation between posts and comments. Original posts primarily focused on clinical sense-making, including interpretation of semen analyses, hormonal testing, and assisted reproduction options. In contrast, comments emphasized emotional validation, experiential knowledge-sharing, and normalization of alternative family-building pathways. Emotional expression varied by discussion topic, with heightened fear and sadness in conversations involving genetic testing, surgical sperm retrieval, and donor sperm. Hyperlink analysis indicated frequent engagement with peer-reviewed medical information, reflecting active evidence-seeking alongside peer exchange. Taken together, findings suggest that anonymous online communities function as critical infrastructures of support for men experiencing infertility, enabling forms of disclosure and vulnerability often constrained in offline contexts. These spaces facilitate interpretation of medical information, collective coping, and decision-making regarding treatment and donor options. The study highlights the role of digital anonymity in mitigating stigma and expanding communicative possibilities for men navigating infertility alongside clinical care.

PurposeIdiopathic hypogonadotropic hypogonadism (IHH) is characterized by impaired reproductive maturation, and approximately half of all cases lack an identified genetic cause. We investigated the genetic basis of IHH in two large cohorts to identify novel disease-causing genes. MethodsWe analyzed exome and genome sequencing data from 1,822 patients with IHH from two independent cohorts. Rare variants were filtered using pedigree-informed inheritance models. PLEKHA6 expression in the postmortem human hypothalamus were tested at the mRNA and protein level. Functional studies assessed kisspeptin secretion in cell-based assays. ResultsWe identified 18 distinct PLEKHA6 variants in 24 patients from 20 unrelated families (1.3% of cohort). Variants segregated with disease under autosomal recessive and autosomal dominant (with variable penetrance) inheritance patterns. PLEKHA6 was robustly expressed in the hypothalamus and showed clear colocalization with neurokinin B, which served as the marker for the GnRH pulse generator. Functional studies demonstrated that patient variants significantly impaired kisspeptin secretion. ConclusionPLEKHA6 is a novel IHH gene and the first reported regulator of kisspeptin secretion from the kisspeptin-neurokinin B-dynorphin (KNDy) neurons, which have recently been established as the GnRH pulse generator. These findings establish impaired kisspeptin release as a new disease mechanism in IHH and highlight the critical role of neuropeptide trafficking in reproductive function.

ObjectiveTo determine whether quantitative ultrasound (QUS), which characterizes tissue microstructure using radiofrequency data, can identify regional heterogeneity within seminiferous tubules that corresponds to localized spermatogenesis in men with non-obstructive azoospermia (NOA). DesignTwo-cohort study using a biological extremes cohort to establish plausibility of a QUS biomarker, followed by an independent NOA-biopsy cohort with site-matched imaging and tissue sampling. SettingAcademic male fertility referral center. PatientsThe biological extremes cohort included fertile men with presumed intact spermatogenesis (n=15) and men with NOA and subsequent negative microdissection testicular sperm extraction (mTESE; n=10). The NOA-biopsy cohort consisted of 27 men with NOA undergoing site-matched testicular biopsy via testicular sperm aspiration (TESA) or testicular sperm extraction (TESE), yielding 12 sperm-positive and 36 sperm-negative biopsy sites. InterventionsHigh-frequency testicular ultrasound (36 MHz) with acquisition of raw radiofrequency data, allowing objective, quantitative analysis of tissue scattering patterns beyond conventional grayscale imaging. Regions of interest were manually annotated and, in the NOA-biopsy cohort, spatially matched to biopsy locations. Main Outcome MeasuresAssociation between sperm presence at biopsy sites and a pre-specified QUS measure of local tissue heterogeneity: the 75th percentile of a sliding window coefficient of variation map of the Nakagami k-factor within the superficial testicular parenchyma (K_Zone1_CV). This metric reflects the upper range of local variability in ultrasound backscatter, which is influenced by the underlying organization of seminiferous tubules. ResultsIn the biological extremes cohort, K_Zone1_CV distinguished fertile controls (median 1.79, IQR 1.64-1.85) from NOA men with globally negative mTESE (median 1.51, IQR 1.42-1.58; P < 0.001), with an area under the receiver operating characteristic curve (AUC) of 0.91 (95% CI 0.79-1.00). In the independent NOA-biopsy cohort, K_Zone1_CV discriminated sperm-positive from sperm-negative biopsy sites with an AUC of 0.93 (95% CI 0.85-0.99). At a threshold of 1.60, sensitivity was 100%, specificity was 86.1%, positive predictive value was 70.6%, and negative predictive value was 100%. Serum hormone levels, testicular volumes, and biopsy technique did not differ significantly between groups. ConclusionsRegional testicular tissue heterogeneity measured by quantitative ultrasound is associated with localized spermatogenesis in men with NOA. At the selected threshold, no sperm-positive biopsy site was misclassified as negative. These findings support the hypothesis that QUS can noninvasively detect the focal seminiferous tubule heterogeneity that predicts sperm retrieval success. This imaging approach could inform future image-guided sperm retrieval strategies. Further validation in larger cohorts and assessment of intra-patient variability are needed.