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STUDY QUESTION Is there an increase in the total number of metaphase II (MII) oocytes between a conventional ovarian stimulation (OS) and a double uninterrupted stimulation? SUMMARY ANSWER There is no increase in the total number of MII oocytes when comparing one conventional OS to a continuous stimulation with double oocyte aspiration. WHAT IS KNOWN ALREADY Based on the concept of multiple follicular waves, the combination of two stimulations in the same ovarian cycle has gained interest in patients with a low ovarian reserve. This so-called dual stimulation approach is usually characterized by a discontinuation of FSH administration for ∼5 days and appears to have a favourable impact on the number of retrieved oocytes without affecting the embryo quality or ploidy status. The outcomes of dual uninterrupted OS have not yet been studied. STUDY DESIGN, SIZE, DURATION This was an open-label randomized controlled trial (RCT) with superiority design, performed in a single tertiary centre. Subjects were randomized with a 1:1 allocation into two groups between October 2019 and September 2021. All patients underwent a conventional stimulation with recombinant FSH. When two or more follicles of 17 mm were present, the final inclusion criterion was assessed; randomization occurred only in the presence of ≤9 follicles of ≥11 mm. In Group A, ovulation was triggered with hCG, and oocyte retrieval (OR) was performed 34–36 h later, followed by a fresh single or double embryo transfer (SET or DET) on Day 3/5. In Group B, ovulation was triggered with GnRH agonist, followed by another OS, without discontinuation of the FSH administration. In the presence of one or more follicles of ≥17 mm, the second stimulation was completed with hCG. A freeze-all strategy (Day 3/5) was applied for both retrievals, followed by transfer of one or two embryos in an artificially prepared frozen-thawed cycle. In the absence of one or more follicles of ≥17 mm after 13 additional days of stimulation, the second cycle was cancelled. All ORs were executed by a senior fertility specialist who was blinded for the first treatment, and all follicles >10 mm were aspirated, according to routine clinical practice. The primary outcome was the total number of MII oocytes. Patients were followed up until all embryos were transferred, or until live birth was achieved. Other secondary outcomes included the number of cumulus–oocyte complexes (COCs), the number of good quality embryos (Day 3/5), the ongoing pregnancy rate, and gonadotropin consumption. PARTICIPANTS/MATERIALS, SETTING, METHODS Patients between 25 and 40 years old, with an anti-Müllerian hormone level of ≤1.5 ng/ml, antral follicle count of ≤6, or ≤5 oocytes after a previous stimulation, were included. At the start, 70 patients were eligible for participation in the trial, of whom 48 patients fulfilled the final inclusion criterium and were randomized. After drop-out of two patients, 23 patients were randomized to a single round of OS (Group A), and 23 patients were randomized to two uninterrupted rounds of OS (Group B). MAIN RESULTS AND THE ROLE OF CHANCE Baseline characteristics were similar between both groups. The cumulative number of COCs and MII oocytes after completion of the second OR was similar in Group A and Group B [5.3 ± 2.7 versus 5.3 ± 3.0 (P  = 0.95); 4.1 ± 2.4 versus 4.3 ± 2.7 (P  = 0.77)]. Likewise, a comparable number of excellent and good quality embryos was available on Day 3 (3.0 ± 2.0 versus 2.7 ± 2.0; P  = 0.63). In Group B, the cancellation rate due to insufficient response to the second round of stimulation was 39.1% (9/23). When focusing on the first stimulation in both groups, there were no significant differences regarding basal FSH, gonadotropin consumption, and the number of preovulatory follicles. After the first OR, the mean number of COC and MII oocytes was significantly higher in Group A (who had hCG triggering), compared to Group B (who had GnRH agonist triggering) [5.3 ± 2.7 versus 3.3 ± 2.2; difference 95% CI (0.54 to 3.45), P  = 0.004 and 4.1 ± 2.4 versus 3.0 ± 2.2; difference 95% CI (−0.15 to 2.6), P  = 0.05, respectively]. Likewise, the number of excellent and good quality embryos on Day 3 was significantly higher (3.0 ± 2.0 versus 1.9 ± 1.7; P  = 0.02) in Group A. LIMITATIONS, REASONS FOR CAUTION This study was powered to demonstrate superiority for the number of MII oocytes after dual stimulation. Investigating the impact of dual stimulation on pregnancy rates would have required a larger sample size. Furthermore, the heterogeneity in embryo vitrification and transfer policies precluded a correct comparison of embryologic outcomes between both groups. WIDER IMPLICATIONS OF THE FINDINGS This is the first RCT investigating the role of continuous stimulation with double aspiration in low responders. Our results show no statistically significant differences in the cumulative number of MII oocytes between one conventional stimulation with fresh ET and two consecutive stimulations with a freeze-only approach. Furthermore, the observed suboptimal oocyte yield after agonist ovulation triggering in low responders in the dual uninterrupted OS group is a reason for concern and further scrutiny, given that previous RCTs have shown similar outcomes in normal and high responders after hCG and GnRH agonist triggers. STUDY FUNDING/COMPETING INTEREST(S) This work was supported in part by a research grant from Organon. H.T. received honoraria for lectures and presentations from Abbott, Cooper Surgical, Gedeon-Richter, Cook, Goodlife, and Ferring. L.B. received fees for lectures from Merck & Organon and support for attending ESHRE 2023. M.D.V. reports fees for lectures from Ferring, Merck, Organon, IBSA, Gedeon Richter, and Cooper Surgical and support for attending ASRM 2023. S.M. received honoraria for lectures and presentations from Abbott, Cooper Surgical, Gedeon-Richter, IBSA, and Merck. C.B. was on the Advisory board and received consulting fees from Theramex and received honoraria for lectures and presentations from Abbott, Ferring, Gedeon-Richter, IBSA, and Merck. TRIAL REGISTRATION NUMBER NCT03846544 TRIAL REGISTRATION DATE 19 February 2019 DATE OF FIRST PATIENT'S ENROLMENT 28 October 2019 [ABSTRACT FROM AUTHOR]

STUDY QUESTION What is the added value of enzymatic processing of testicular biopsies on testicular sperm retrieval (SR) rates for patients with non-obstructive azoospermia (NOA)? SUMMARY ANSWER In addition to mechanical mincing, enzymatic digestion increased SR rates in testicular biopsies of NOA patients. WHAT IS KNOWN ALREADY Many studies focus on the surgical approach to optimize recovery of testicular sperm in NOA, and in spite of that, controversy still exists about whether the type of surgery makes any difference as long as multiple biopsies are taken. Few studies, however, focus on the role of the IVF laboratory and the benefit of additional lab procedures, e.g. enzymatic digestion, in order to optimize SR rates. STUDY DESIGN, SIZE, DURATION This retrospective single-center cohort study included all patients who underwent their first testicular sperm extraction (TESE) by open multiple-biopsy method between January 2004 and July 2022. Only patients with a normal karyotype, absence of Y-q deletions and a diagnosis of NOA based on histology were included. The primary outcome was SR rate after mincing and/or enzymes. The secondary outcome was cumulative live birth (CLB) after ICSI with fresh TESE and subsequent ICSI cycles with frozen TESE. PARTICIPANTS/MATERIALS, SETTING, METHODS Multiple biopsies were obtained from the testis, unilaterally or bilaterally, on the day of oocyte retrieval. Upon mechanical mincing, biopsies were investigated for 30 min; when no or insufficient numbers of spermatozoa were observed, enzymatic treatment was performed using Collagenase type IV. Multivariable regression analysis was performed to predict CLB per TESE by adjusting for the following confounding factors: male FSH level, female age, and requirement of enzymatic digestion to find sperm. MAIN RESULTS AND THE ROLE OF CHANCE We included 118 patients, of whom 72 (61.0%) had successful SR eventually. Spermatozoa were retrieved after mechanical mincing for 28 patients (23.7%; 28/118) or after additional enzymatic digestion for another 44 patients (37.2%; 44/118). Thus, of the 90 patients requiring enzymatic digestion, sperm were retrieved for 44 (48.9%). Male characteristics were not different between patients with SR after mincing or enzymatic digestion, in regard to mean age (34.5 vs 34.5 years), testis volume (10.2 vs 10.6 ml), FSH (17.8 vs 16.9 IU/l), cryptorchidism (21.4 vs 34.1%), varicocele (3.6 vs 4.6%), or histological diagnosis (Sertoli-cell only 53.6 vs 47.7%, maturation arrest 21.4 vs 38.6%, sclerosis/atrophy 25.0 vs 13.6%). Of the 72 patients with sperm available for ICSI, 23/72 (31.9%) achieved a live birth (LB) after the injection with fresh testicular sperm (and fresh or frozen embryo transfers). Of the remaining 49 patients without LB, 34 (69.4%) had supernumerary testicular sperm frozen. Of these 34 patients, 19 (55.9%) continued ICSI with frozen testicular sperm, and 9/19 (47.4%) had achieved an LB after ICSI with frozen testicular sperm. Thus, the total CLB was 32/118 (27.1%) per TESE or 32/72 (44.4%) per TESE with sperm retrieved. Of the female characteristics (couples with sperm available), only female age (30.3 vs 32.7 years; P  = 0.042) was significantly lower in the group with a LB, compared to those without. The CLB with testicular sperm obtained after enzymatic digestion was 31.8% (14/44), while the CLB with sperm obtained after mincing alone was 64.3% (18/28). Multivariable logistic regression analysis showed that when enzymatic digestion was required, it was associated with a significant decrease in CLB per TESE (OR: 0.23 (0.08–0.7); P  = 0.01). LIMITATIONS, REASONS FOR CAUTION Limitations of the study are related to the retrospective design. However, the selection of only patients with NOA, and specific characteristics (normal karyotype and absence Y-q deletion) and having their first TESE, strengthens our findings. WIDER IMPLICATIONS OF THE FINDINGS Enzymatic processing increases the SR rate from testicular biopsies of NOA patients compared to mechanical mincing only, demonstrating the importance of an appropriate laboratory protocol. However, NOA patients should be counseled that when sperm have been found after enzymatic digestion, their chances to father a genetically own child may be lower compared to those not requiring enzymatic digestion. STUDY FUNDING/COMPETING INTEREST(S) None reported. TRIAL REGISTRATION NUMBER N/A. [ABSTRACT FROM AUTHOR]

STUDY QUESTION What is the long-term impact of presumed gonadotoxic treatment during childhood on the patient's testicular function at adulthood? SUMMARY ANSWER Although most patients showed low testicular volumes and some degree of reproductive hormone disruption 12.3 (2.3–21.0) years after gonadotoxic childhood therapy, active spermatogenesis was demonstrated in the semen sample of 8 out of the 12 patients. WHAT IS KNOWN ALREADY In recent decades, experimental testicular tissue banking programmes have been set up to safeguard the future fertility of young boys requiring chemo- and/or radiotherapy with significant gonadotoxicity. Although the risk of azoospermia following such therapies is estimated to be high, only limited long-term data are available on the reproductive potential at adulthood. STUDY DESIGN, SIZE, DURATION This single-centre prospective cohort study was conducted between September 2020 and February 2023 and involved 12 adult patients. PARTICIPANTS/MATERIALS, SETTING, METHODS This study was carried out in a tertiary care centre and included 12 young adults (18.1–28.3 years old) who had been offered testicular tissue banking prior to gonadotoxic treatment during childhood. All patients had a consultation and physical examination with a fertility specialist, a scrotal ultrasound to measure the testicular volumes and evaluate the testicular parenchyma, a blood test for assessment of reproductive hormones, and a semen analysis. MAIN RESULTS AND THE ROLE OF CHANCE Testicular tissue was banked prior to the gonadotoxic treatment for 10 out of the 12 included patients. Testicular volumes were low for 9 patients, and 10 patients showed some degree of reproductive hormone disruption. Remarkably, ongoing spermatogenesis was demonstrated in 8 patients at a median 12.3 (range 2.3–21.0) years post-treatment. LIMITATIONS, REASONS FOR CAUTION This study had a limited sample size, making additional research with a larger study population necessary to verify these preliminary findings. WIDER IMPLICATIONS OF THE FINDINGS These findings highlight the need for multicentric research with a larger study population to establish universal inclusion criteria for immature testicular tissue banking. STUDY FUNDING/COMPETING INTEREST(S) This study was conducted with financial support from the Research Programme of the Research Foundation-Flanders (G010918N), Kom Op Tegen Kanker, and Scientific Fund Willy Gepts (WFWG19-03). The authors declare no competing interests. TRIAL REGISTRATION NUMBER NCT04202094; https://clinicaltrials.gov/ct2/show/NCT04202094?id=NCT04202094&draw=2&rank=1 This study was registered on 6 December 2019, and the first patient was enrolled on 8 September 2020. [ABSTRACT FROM AUTHOR]

Study Question: What is the reproductive potential following combinations of ovarian stimulation, IVM and ovarian tissue cryopreservation (OTC) in female patients seeking fertility preservation (FP)?Summary Answer: In selected patients, combining different FP procedures is a feasible approach and reproductive outcomes after FP in patients who return to attempt pregnancy are promising.What Is Known Already: FP is increasingly performed in fertility clinics but an algorithm to select the most suitable FP procedure according to patient characteristics and available timeframe is currently lacking. Vitrification of mature oocytes (OV) and OTC are most commonly performed, although in some clinical scenarios a combination of procedures including IVM, to spread the sources of gametes, may be considered in order to enhance reproductive options for the future.Study Design, Size, Duration: Retrospective, observational study in a university-based, tertiary fertility centre involving all female patients who underwent urgent medical FP between January 2012 and December 2018. Descriptive analysis of various FP procedures, either stand-alone or combined, was performed, and reproductive outcomes of patients who attempted pregnancy in the follow-up period were recorded.Participants/materials, Setting, Methods: In total, 207 patients underwent medical FP. Patient-tailored strategies and procedures were selected after multidisciplinary discussion. When deemed feasible, FP procedures were combined to cryopreserve different types of reproductive tissue for future use. The main primary outcome measure was the number of mature oocytes. Live birth rates were evaluated in patients who returned for reproductive treatment.Main Results and the Role Of Chance: Among patients seeking FP, 95/207 (46%) had breast cancer, 43/207 (21%) had haematological malignancies and 31/207 (15%) had a gynaecological tumour. Mean ± SD age was 27.0 ± 8.3 years. Eighty-five (41.1%) patients underwent controlled ovarian stimulation (COS), resulting in 10.8 ± 7.1 metaphase II (MII) oocytes for vitrification. Eleven (5.3%) patients had multiple COS cycles. Transvaginal oocyte retrieval for IVM was performed in 17 (8.2%) patients, yielding 9.2 ± 10.1 MII oocytes. Thirty-four (16.4%) patients underwent OTC combined with IVM of oocytes retrieved from ovarian tissue 'ex vivo' (OTO-IVM), yielding 4.0 ± 4.3 MII oocytes in addition to ovarian fragments. Seventeen (8.2%) patients had OTC combined with OTO-IVM and transvaginal retrieval of oocytes for IVM from the contralateral ovary, resulting in 13.5 ± 9.7 MII oocytes. In 13 (6.3%) patients, OTC with OTO-IVM was followed by controlled stimulation of the contralateral ovary, yielding 11.3 ± 6.6 MII oocytes in total. During the timeframe of the study, 31/207 (15%) patients have returned to the fertility clinic with a desire for pregnancy. Of those, 12 (38.7%) patients had preserved ovarian function and underwent ART treatment with fresh oocytes, resulting in nine (75%) livebirth. The remaining 19 (61.3%) patients requested warming of their cryopreserved material because of ovarian insufficiency. Of those, eight (42.1%) patients had a livebirth, of whom three after OTO-IVM. To date, 5/207 patients (2.4%) achieved an ongoing pregnancy or livebirth after spontaneous conception.Limitations, Reasons For Caution: Our FP programme is based on a patient-tailored approach rather than based on an efficiency-driven algorithm. The data presented are descriptive, which precludes firm conclusions.Wider Implications Of the Findings: Combining different FP procedures is likely to enhance the reproductive fitness of patients undergoing gonadotoxic treatment but further follow-up studies are needed to confirm this.Study Funding/competing Interest(s): No external funding was used for this study and the authors have no competing interests.Trial Registration Number: N/A. [ABSTRACT FROM AUTHOR]

This sibling oocyte study was designed to determine how embryo quality is influenced after sperm selection using microfluidic sperm sorting (MSS) technology compared to a standard density gradient centrifugation (DGC). A single-centre prospective non-inferiority sibling oocyte study was performed between October 2023 and February 2024, comparing DGC to MSS. Primary endpoint was embryo utilisation rate. Only ICSI cycles with ejaculated sperm and at least 6 mature oocytes (MII) were included. Sample-size calculation indicated a number of 253 MII for each arm. Each raw semen sample was split in two fractions processed by DGC and by MSS using Zymot 850µl® device. During ICSI, half of the MII were injected with sperm processed by DGC and the other half by MSS. The inseminated oocytes were individually cultured in cleavage/blastocyst medium (Origio) for maximum 7 days. The mean female age was 34.5±4.4 years and partner age was 37.5±5.5 years. Sperm concentration (x106/ml) was similar following DGC (2.9±1.2) or MSS (3.5±5.0) (p=0.16). Progressive motility (% A+B) was significantly lower following DGC vs MSS (74.0%±17.2 vs 89.9%±10.4 (p<0.01), respectively. The DFI of the raw semen samples was 5.6%±3.6. A number of 51 ICSI-cycles were included with 658 cumulus-oocyte-complexes retrieved of which 532 MII were randomized to either DGC (n= 265) or MSS (n=267) groups. Fertilisation rate was not significantly different between DGC and MSS (208/265, 78.5% vs 209/267, 78.3%, respectively; p=0.96). Similarly, good embryo quality on day 3 (159/208, 76.4% vs 161/209, 77.0%, respectively; p=0.97) and good blastocyst quality (≥Bl3BB) (86/208, 41.3% vs 76/209, 36.4%, respectively; p=0.30) were not different between the two groups. Utilisation rates (number of transferred and cryopreserved embryos) were similar between the two groups: both per MII (104/265, 39.2% vs 107/267, 40.1%, respectively; p=0.91) and per fertilised oocyte (104/208, 50.0% vs 107/209, 51.2%, respectively; p=0.88) in DGC vs MSS. Since fertilisation, embryo quality and utilisation rate are similar in both groups, the use of Zymot 850µl® device offers the advantage of eliminating the negative effects and time-consuming nature of centrifugation. Another advantage is that scheduling of semen samples can be planned more efficiently. [ABSTRACT FROM AUTHOR]

Study Question: When does germ cell loss and fibrosis occur in patients with Klinefelter syndrome (KS)?Summary Answer: In KS, germ cell loss is not observed in testicular tissue from fetuses in the second semester of pregnancy but present at a prepubertal age when the testicular architecture is still normal, while fibrosis is highly present at an adolescent age.What Is Known Already: Most KS patients are azoospermic at adult age because of a massive germ cell loss. However, the timing when this germ cell loss starts is not known. It is assumed that germ cell loss increases at puberty. Therefore, testicular sperm extraction (TESE) at an adolescent age has been suggested to increase the chances of sperm retrieval at onset of spermatogenesis. However, recent data indicate that testicular biopsies from peripubertal KS patients contain only a few germ cells.Study Design, Size, Duration: In this study, we give an update on fertility preservation in adolescent KS patients and evaluate whether fertility preservation would be beneficial at prepubertal age. The possibility of retrieving testicular spermatozoa by TESE was evaluated in adolescent and adult KS men. The presence of spermatogonia and the degree of fibrosis were also analysed in testicular biopsies from KS patients at different ages. The patients were divided into four age groups: foetal (n = 5), prepubertal (aged 4-7 years; n = 4), peripubertal (aged 12-16 years; n = 20) and adult (aged 18-41 years; n = 27) KS patients.Participants/materials, Setting, Methods: In peripubertal and adult KS patients, retrieval of spermatozoa was attempted by semen analysis after masturbation, vibrostimulation, electroejaculation or by TESE. MAGE-A4 immunohistochemistry was performed to evaluate the presence of germ cells in testicular biopsies from foetal, prepubertal, peripubertal and adult KS patients. Tissue morphology was evaluated by haematoxylin-periodic acid Schiff (H/PAS) staining.Main Results and the Role Of Chance: Testicular spermatozoa were collected by TESE in 48.1% of the adult KS patients, while spermatozoa were recovered after TESE in only one peripubertal patient (5.0%). Germ cells were detectable in testicular biopsies from 21% of adult men for whom no spermatozoa could be retrieved by TESE and in 31.5% of peripubertal KS boys. Very small numbers of spermatogonia (0.03-0.06 spermatogonia/tubule) were detected in three out of four (75%) prepubertal patients. At a foetal age, the number of germ cells was similar for KS and control samples. Increased signs of fibrosis were not present at foetal and prepubertal ages, but peripubertal and adult KS patients showed high levels of fibrosis.Large Scale Data: N/A.Limitations, Reasons For Caution: Only four prepubertal biopsies were included in this study, but they all showed a very low germ cell number. A high variability in the number of spermatogonia per mm2 was observed in the limited (n = 5) number of foetal biopsies. However, testicular biopsies from prepubertal and foetal Klinefelter patients are difficult to obtain.Wider Implications Of the Findings: Testicular tissue banking at a prepubertal age has been suggested as a potential method for fertility preservation in early diagnosed KS boys. However, our results show that a reduction in germ cell number has already taken place in childhood. Therefore, offering testicular tissue banking in young KS boys to prevent subsequent sterility might be a questionable strategy. However, this should be confirmed in a larger study population.Study Funding/competing Interest(s): This project was funded by the scientific Fund Willy Gepts from the UZ Brussel (D.V.S., J.D.S.), grants from the Vrije Universiteit Brussel (E.G.) and a Methusalem grant (K.S.). D.V.S is a post-doctoral fellow of the Fonds Wetenschappelijk Onderzoek (FWO; 12M2815N). No conflict of interest is declared. [ABSTRACT FROM AUTHOR]

Study Question: Does the manipulation of gametes or embryos during ARTs increase the risk for monozygotic twinning (MZT)?Summary Answer: Frozen embryo transfer (ET) is associated with a lower MZT rate, while blastocyst culture is associated with an increased risk of monozygotic pregnancy.What Is Known Already: Monozygotic twins have a higher risk for perinatal complications. Although an increased incidence of monozygotic pregnancies after ART has been previously reported, data regarding the possible impact of different laboratory procedures are conflicting.Study Design, Size, Duration: All clinical pregnancies after single ET carried out in our centre between 2004 and 2013 (n = 6096) were retrospectively analysed for the incidence of MZT. The effect of different laboratory procedures on the incidence of MZT was evaluated.Participants/materials, Setting, Methods: The following ART risk factors were assessed: maternal age, type of ET (fresh versus frozen), zona pellucida (ZP) manipulation (specifically, ICSI, embryo biopsy and assisted hatching), use of donor oocytes, embryo stage at time of ET (cleavage, compaction, early or advanced blastocyst) and culture media.Main Results and the Role Of Chance: The overall MZT rate was 2.2% (136/6096). Frozen ET was associated with a significant reduction in MZT incidence (adjusted odds ratio (aOR) 0.48, 95% CI 0.29-0.80), while blastocyst transfer (early or advanced blastocyst) was associated with a significant increase in MZT risk (aOR 2.70, 95% CI 1.36-5.34; aOR 2.05, 95% CI 1.29-3.26, respectively). No significant differences were found between the MZT and singleton (non-MZT) groups regarding maternal age, the use of different ZP manipulation techniques, not type of culture media used.Limitation, Reasons For Caution: This study is limited by its retrospective nature and the fact that monozygosity was not confirmed by genetic testing. Furthermore, since monozygotic pregnancy is a rare event, other ART parameters that may influence its incidence could not be assessed during our analysis.Wider Implication Of the Findings: Our findings warrant future studies designed to investigate the association between specific ART procedures and MZT, namely the potential risk of blastocyst transfer to increase MZT.Study Funding/competing Interests: No external funding was used for this study. There are no conflicts of interest. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this prospective sibling oocyte study was to evaluate whether reduced culture volume improves blastocyst formation. Methods: Twenty-three patients with extended embryo culture until day 5 were selected for the study. After injection, 345 sibling oocytes were individually cultured in either 25 or 7 μl droplets of Origio cleavage medium under oil. On day 3 of development, embryos were transferred to droplets with the corresponding volume of Origio blastocyst culture medium. Fertilization and embryo quality on day 3 and day 5/6 were evaluated. Results: No statistically significant difference ( p = 0.326) in fertilization rate was observed (81.3 versus 83.0 %). There was no significant difference in terms of the number of excellent and good-quality embryos obtained on day 3 between both groups ( p = 0.655). Embryo culture in 25 μl droplets led to more embryos with a higher cell number when compared to 7 μl culture ( p = 0.024). On day 3, 132 and 131 embryos were considered for further culture until day 5/6. Blastulation rates were significantly higher in the 25 μl group (75.0 versus 61.6 %; p = 0.017) and significantly more day 5 embryos with excellent and good quality were found in this group (54.5 versus 40.5 %; p = 0.026). Finally, the utilization rates expressed per mature oocyte (41.4 versus 29.8 %; p = 0.043), per fertilized oocyte (50.7 versus 36.6 %; p = 0.023), and per day 3 embryo undergoing extended culture to day 5/6 (54.5 versus 39.7 %; p = 0.019) were all significantly higher in the 25 μl group. Conclusion: Reduced culture volume (7 μl) negatively impacts early development by reducing the cell number on day 3 and both blastocyst formation and quality. [ABSTRACT FROM AUTHOR]

Background: Sperm extracted from testicular biopsies of azoospermic men can successfully be used for ICSI. The concern exists that testicular sperm from azoospermic men suffering from severe testicular failure may have a higher frequency of aneuploidy, which may lead to an increased risk for chromosomally abnormal offspring.Methods: Testicular sperm from patients showing spermatogenic failure (n = 17) and from patients with normal spermatogenesis (n = 26) were analysed by fluorescence in-situ hybridization (FISH). Numerical chromosomal abnormalities for chromosomes X, Y and 18 were evaluated by FISH in a total of 1697 testicular sperm derived from 43 azoospermic patients.Results: No difference was observed between the frequency of chromosomal abnormalities in testicular sperm from patients with normal spermatogenesis (5.6%) and from patients with spermatogenic failure (8.2%). However, the frequency of aneuploidy for chromosome 18 was higher in the group of azoospermic patients with spermatogenic failure than in the group with normal spermatogenesis (3.2 versus 1.3%). Within the obstructive group, sex chromosome aneuploidy (4.5%) occurred more frequently than chromosome 18 aneuploidy (1.3%; P < 0.001). Among testicular sperm derived from patients with spermatogenic failure, sex chromosomal aneuploidy (5.8%) was similar to that for chromosome 18 (3.2%).Conclusions: So far, no difference in the total frequency of chromosomal abnormalities has been observed between patients with normal spermatogenesis and patients with severe testicular failure. However, aneuploidy for chromosome 18 was higher in the group with spermatogenic failure. [ABSTRACT FROM AUTHOR]

In conventional IVF (cIVF), extended exposure (16-20 hours) of oocytes to spermatozoa metabolic waste may negatively impact embryo development, emphasizing the importance of incubation time in the IVF procedure. We aimed to compare fertilization rates, embryo quality and utilization rates between short IVF (sIVF) incubation and cIVF as part of a validation study. The study was performed between October 2022-2023. sIVF incubation was performed and oocytes were denuded 6 hours later. Control patients underwent cIVF within the same study period, with denudation performed 16-20h post insemination. Fertilization rates, embryo quality and utilization rates were assessed and compared between the two groups. Regression analysis was performed considering age, age of partner, total COCs retrieved and number of previous cycles as potential confounders. Based on the time of oocyte retrieval, 24 cycles were included in sIVF (n=244 COCs) and 187 cycles in cIVF (n=1922 COCs). Patients were on average 34.1±4.2 and 32.3±4.8 years old, respectively. Fertilization rates per COC (52% and 53% respectively, p=0.742) and per mature oocyte (MII, 60% and 63% respectively, p=0.848) showed no significant differences. The incidence of abnormally fertilized oocytes (≥3 pronuclei) was significantly lower in sIVF (10% vs 13% respectively, p=0.040) when only mature oocytes were taken into account. Day 3 and day 5 rates of good quality embryos per fertilized oocyte (2PN) were comparable between sIVF and cIVF (day 3: 75% vs 77%, p=0.970; day 5: 28% vs 42%, p=0.174). No significant difference was found for utilization rates per COC, per MII, or per 2PN [19% vs 28% (p=0.450), 22% vs 33% (p=0.381), 37% vs 52% (p=0.173), respectively]. Linear regression analysis revealed no significant confounding effects on the tested variables. Heterogeneity and limited sample size are the main drawbacks of this study with a need for a prospective sibling oocyte study to further elucidate potential differences between sIVF and cIVF. To conclude, sIVF is comparable to cIVF in terms of fertilization rates, embryo quality and utilization rates. The lower rate of abnormally fertilized oocytes shows a potential advantage of a sIVF protocol. [ABSTRACT FROM AUTHOR]