How slow is too slow? A comprehensive portrait of Day 7 blastocysts and their clinical value standardized through artificial intelligence.

STUDY QUESTION: What is the clinical value of Day 7 blastocysts? SUMMARY ANSWER: Ending embryo culture at 144 hours post-insemination (h.p.i.; i.e. 6 days) would involve 7.3% and 4.4% relative reductions in the number of patients obtaining euploid blastocysts and live birth(s) (LBs), respectively. WHAT IS KNOWN ALREADY: Many studies showed that Day 7 blastocysts are clinically valuable, although less euploid and less competent than faster-growing embryos. Nevertheless, a large variability exists in: (i) the definition of 'Day 7'; (ii) the criteria to culture embryos to Day 7; (iii) the clinical setting; (iv) the local regulation; and/or (v) the culture strategies and incubators. Here, we aimed to iron out these differences and portray Day 7 blastocysts with the lowest possible risk of bias. To this end, we have also adopted an artificial intelligence (AI)-powered software to automatize developmental timings annotations and standardize embryo morphological assessment. STUDY DESIGN, SIZE AND DURATION: Observational study including 1966 blastocysts obtained from 681 patients cultured in a time-lapse incubator between January 2013 and December 2020 at a private Italian IVF center. PARTICIPANTS/MATERIALS, SETTING, METHODS: According to Italian Law 40/2004, embryos were not selected based on their morphology and culture to ≥168 h.p.i. is standard care at our center. ICSI, continuous culture with Day 5 media refresh, trophectoderm biopsy without assisted hatching and comprehensive chromosome testing (CCT) to diagnose full-chromosome non-mosaic aneuploidies, were all performed. Blastocysts were clustered in six groups based on the time of biopsy in h.p.i. at 12 hr intervals starting from <120 h.p.i. (set as control) up to >168 h.p.i. Blastocyst quality was assessed using Gardner's scheme and confirmed with AI-powered software. AI was also used to automatically annotate the time of expanding blastocyst (tEB) and the hours elapsing between this moment and the achievement of full expansion when blastocysts were biopsied and vitrified. Also, blastocyst area at tEB and at the time of biopsy was automatically assessed, as well as the hour of the working day when the procedure was performed. The main outcomes were the euploidy rate and the LB rate (LBR) per vitrified-warmed euploid single blastocyst transfer. The results were adjusted for confounders through multivariate logistic regressions. To increase their generalizability, the main outcomes were reported also based on a 144-h.p.i. cutoff (i.e. 6 exact days from ICSI). Based on this cutoff, all the main patient outcomes (i.e. number of patients obtaining blastocysts, euploid blastocysts, LBs, with supernumerary blastocysts without a LB and with surplus blastocysts after an LB) were also reported versus the standard care (>168 h.p.i.). All hypothetical relative reductions were calculated. MAIN RESULTS AND THE ROLE OF CHANCE: A total of 14.6% of the blastocysts reached full expansion beyond 144 h.p.i. (5.9% in the range 144-156 h.p.i., 7.9% in the range 156-168 h.p.i. and 0.8% beyond 168 h.p.i.). Slower blastocysts were of a worse quality based on the evaluation of both embryologists and AI. Both later tEB and longer time between tEB and full blastocyst expansion concurred to Day 7 development, quite independently of blastocyst quality. Slower growing blastocysts were slightly larger than faster-growing ones at the time of biopsy, but no difference was reported in the risk of hatching, mainly because two dedicated slots have been set along the working day for these procedures. The lower euploidy rate among Day 7 blastocysts is due to their worse morphology and more advanced oocyte age, rather than to a slower development per se. Conversely, the lower LBR was significant even after adjusting for confounders, with a first relevant decrease for blastocysts biopsied in the range 132-144 h.p.i. (N = 76/208, 36.5% versus N = 114/215, 53.0% in the control, multivariate odds ratio 0.61, 95% CI 0.40-0.92, adjusted-P = 0.02), and a second step for blastocysts biopsied in the range 156-168 h.p.i. (N = 3/21, 14.3%, multivariate odds ratio: 0.24, 95% CI 0.07-0.88, adjusted-P = 0.03). Nevertheless, when the cutoff was set at 144 h.p.i., no significant difference was reported. In this patient population, ending embryo culture at 144 h.p.i. would have caused 10.6%, 7.3%, 4.4%, 13.7% and 5.2% relative reductions in the number of patients obtaining blastocysts, euploid blastocysts, LBs, supernumerary blastocysts without an LB and surplus blastocysts after an LB, respectively. LIMITATIONS, REASONS FOR CAUTION: Gestational and perinatal outcomes were not assessed, and a cost-effectiveness analysis is missing. Moreover, we encourage other groups to investigate this topic with different culture and biopsy protocols, as well as in different clinical settings and regulatory contexts. WIDER IMPLICATIONS OF THE FINDINGS: In view of the increasing personalization and patient-centeredness of IVF, whenever allowed from the local regulations, the choice to culture embryos to Day 7 should be grounded on the careful evaluation of couples' reproductive history. Patients should be aware that Day 7 blastocysts are less competent than faster-growing ones; still, poor prognosis couples, couples less compliant toward other attempts in case of a failure and couples wishing for more than one child, may benefit from them. AI tools can help improving the generalizability of the evidence worldwide. STUDY FUNDING/COMPETING INTEREST(S): This study did not receive any funding. I.E., A.B.M. and I.H.-V. are employees of Fairtility Ltd. TRIAL REGISTRATION NUMBER: N/A.

Inter-centre reliability in embryo grading across several IVF clinics is limited: implications for embryo selection.

RESEARCH QUESTION: What is the intra- and inter-centre reliability in embryo grading performed according to the Istanbul Consensus across several IVF clinics? DESIGN: Forty Day 3 embryos and 40 blastocysts were photographed on three focal planes. Senior and junior embryologists from 65 clinics were invited to grade them according to the Istanbul Consensus (Study Phase I). All participants then attended interactive training where a panel of experts graded the same embryos (Study Phase II). Finally, a second set of pictures was sent to both embryologists and experts for a blinded evaluation (Study Phase III). Intra-centre reliability was reported for Study Phase I as Cohen's kappa between senior and junior embryologists; inter-centre reliability was instead calculated between senior/junior embryologists and experts in Study Phase I versus III to outline improvements after training (i.e. upgrade of Cohen's kappa category according to Landis and Koch). RESULTS: Thirty-six embryologists from 18 centres participated (28% participation rate). The intra-centre reliability was (i) substantial (0.63) for blastomere symmetry (range -0.02 to 1.0), (ii) substantial (0.72) for fragmentation (range 0.29-1.0), (iii) substantial (0.66) for blastocyst expansion (range 0.19-1.0), (iv) moderate (0.59) for inner cell mass quality (range 0.07-0.92), (v) moderate (0.56) for trophectoderm quality (range 0.01-0.97). The inter-centre reliability showed an overall improvement from Study Phase I to III, from fair (0.21-0.4) to moderate (0.41-0.6) for all parameters under analysis, except for blastomere fragmentation among senior embryologists, which was already moderate before training. CONCLUSIONS: Intra-centre reliability was generally moderate/substantial, while inter-centre reliability was just fair. The interactive training improved it to moderate, hence this workflow was deemed helpful. The establishment of external quality assessment services (e.g. UK NEQAS) and the avant-garde of artificial intelligence might further improve the reliability of this key practice for embryo selection.

Clinical, obstetric and perinatal outcomes after vitrified-warmed euploid blastocyst transfer are independent of cryo-storage duration.

RESEARCH QUESTION: The study aimed to retrospectively evaluate the impact of cryo-storage duration on clinical, obstetric and perinatal outcomes after vitrified-warmed euploid blastocyst transfer. DESIGN: This was an observational study including 2688 vitrified-warmed euploid single blastocyst transfers that was conducted at a private IVF centre between May 2013 and March 2020. It included a total of 1884 women (age 38 ± 3 years) undergoing at least one transfer after preimplantation genetic testing for aneuploidies. The euploid blastocysts transferred were clustered into seven groups according to the cryo-storage duration between vitrification and warming: ≤60 days (n = 646; control group), 61-90 days (n = 599), 91-180 days (n = 679), 181-360 days (n = 405), 361-720 days (n = 144), 721-1080 days (n = 118) and >1080 days (n = 97). The primary outcome was the live birth rate (LBR) per transfer. The secondary outcomes were miscarriage rate, obstetric and perinatal issues. The data were adjusted for confounders through logistic or linear regressions. RESULTS: A significantly lower LBR was reported for transfers performed within 91-180 days (n = 291/679, 42.9%; P = 0.017), 181-360 days (n = 169/405, 41.7%; P = 0.016) and 361-720 days (n = 57/144, 39.6%; P = 0.034) versus ≤60 days (n = 319/646, 49.4%). However, this was mainly due to top-quality embryos being transferred first when more euploid blastocysts were available, thereby leaving lower quality ones for subsequent procedures. Indeed, the multivariate odds ratios adjusted for confounders showed similar results across all cryo-storage duration clusters. No difference was reported also for all secondary outcomes. CONCLUSIONS: Cryo-storage duration even beyond 3 years from blastocyst vitrification does not affect clinical, obstetric and perinatal outcomes.

Maternal effect factors that contribute to oocytes developmental competence: an update.

Oocyte developmental competence is defined as the capacity of the female gamete to be fertilized and sustain development to the blastocyst stage. Epigenetic reprogramming, a correct cell division pattern, and an efficient DNA damage response are all critical events that, before embryonic genome activation, are governed by maternally inherited factors such as maternal-effect gene (MEG) products. Although these molecules are stored inside the oocyte until ovulation and exert their main role during fertilization and preimplantation development, some of them are already functioning during folliculogenesis and oocyte meiosis resumption. This mini review summarizes the crucial roles played by MEGs during oocyte maturation, fertilization, and preimplantation development with a direct/indirect effect on the acquisition or maintenance of oocyte competence. Our aim is to inspire future research on a topic with potential clinical perspectives for the prediction and treatment of female infertility.

Leave the past behind: women's reproductive history shows no association with blastocysts' euploidy and limited association with live birth rates after euploid embryo transfers.

STUDY QUESTION: Is there an association between patients' reproductive history and the mean euploidy rates per biopsied blastocysts (m-ER) or the live birth rates (LBRs) per first single vitrified-warmed euploid blastocyst transfers? SUMMARY ANSWER: Patients' reproductive history (as annotated during counselling) showed no association with the m-ER, but a lower LBR was reported after euploid blastocyst transfer in women with a history of repeated implantation failure (RIF). WHAT IS KNOWN ALREADY: Several studies have investigated the association between the m-ER and (i) patients' basal characteristics, (ii) ovarian stimulation strategy and dosage, (iii) culture media and conditions, and (iv) embryo morphology and day of full blastocyst development. Conversely, the expected m-ER due to women's reproductive history (previous live births (LBs), miscarriages, failed IVF cycles and transfers, and lack of euploid blastocysts among prior cohorts of biopsied embryos) still needs investigations. Yet, this information is critical to counsel new patients about a first cycle with preimplantation genetic testing for aneuploidy (PGT-A), but even more so after former adverse outcomes to prevent treatment drop-out. STUDY DESIGN, SIZE, DURATION: This observational study included all patients undergoing a comprehensive chromosome testing (CCT)-based PGT-A cycle with at least one biopsied blastocyst in the period April 2013-December 2019 at a private IVF clinic (n = 2676 patients undergoing 2676 treatments and producing and 8151 blastocysts). m-ER were investigated according to women's reproductive history of LBs: no/≥1, miscarriages: no/1/>1; failed IVF cycles: no/1/2/>2, and implantation failures after previous transfers: no/1/2/>2. Among the 2676 patients included in this study, 440 (16%) had already undergone PGT-A before the study period; the data from these patients were further clustered according to the presence or absence of euploid embryo(s) in their previous cohort of biopsied blastocysts. The clinical outcomes per first single vitrified-warmed euploid blastocyst transfers (n =1580) were investigated according to the number of patients' previous miscarriages and implantation failures. PARTICIPANTS/MATERIALS, SETTING, METHODS: The procedures involved in this study included ICSI, blastocyst culture, trophectoderm biopsy without hatching in Day 3, CCT-based PGT-A without reporting segmental and/or putative mitotic (or mosaic) aneuploidies and single vitrified-warmed euploid blastocyst transfer. For statistical analysis, Mann-Whitney U or Kruskal-Wallis tests, as well as linear regressions and generalised linear models among ranges of maternal age at oocyte retrieval were performed to identify significant differences for continuous variables. Fisher's exact tests and multivariate logistic regression analyses were instead used for categorical variables. MAIN RESULTS AND THE ROLE OF CHANCE: Maternal age at oocyte retrieval was the only variable significantly associated with the m-ER. We defined five clusters (<35 years: 66 ± 31%; 35-37 years: 58 ± 33%; 38-40 years: 43 ± 35%; 40-42 years: 28 ± 34%; and >42 years: 17 ± 31%) and all analyses were conducted among them. The m-ER did not show any association with the number of previous LBs, miscarriages, failed IVF cycles or implantation failures. Among patients who had already undergone PGT-A before the study period, the m-ER did not associate with the absence (or presence) of euploid blastocysts in their former cohort of biopsied embryos. Regarding clinical outcomes of the first single vitrified-warmed euploid blastocyst transfer, the implantation rate was 51%, the miscarriage rate was 14% and the LBR was 44%. This LBR was independent of the number of previous miscarriages, but showed a decreasing trend depending on the number of previous implantation failures, reaching statistical significance when comparing patients with >2 failures and patients with no prior failure (36% versus 47%, P < 0.01; multivariate-OR adjusted for embryo quality and day of full blastocyst development: 0.64, 95% CI 0.48-0.86, P < 0.01). No such differences were shown for previous miscarriage rates. LIMITATIONS, REASONS FOR CAUTION: The sample size for treatments following a former completed PGT-A cycle should be larger in future studies. The data should be confirmed from a multicentre perspective. The analysis should be performed also in non-PGT cycles and/or including patients who did not produce blastocysts, in order to investigate a putative association between women's reproductive history with outcomes other than euploidy and LBRs. WIDER IMPLICATIONS OF THE FINDINGS: These data are critical to counsel infertile couples before, during and after a PGT-A cycle, especially to prevent treatment discontinuation due to previous adverse reproductive events. Beyond the 'maternal age effect', the causes of idiopathic recurrent pregnancy loss (RPL) and RIF are likely to be endometrial receptivity and selectivity issues; transferring euploid blastocysts might reduce the risk of a further miscarriage, but more information beyond euploidy are required to improve the prognosis in case of RIF. STUDY FUNDING/COMPETING INTEREST(S): No funding was received and there are no competing interests. TRIAL REGISTRATION NUMBER: N/A.

Maternal body mass index associates with blastocyst euploidy and live birth rates: the tip of an iceberg?

RESEARCH QUESTION: Does maternal preconceptional body mass index (BMI) associate with mean blastocyst euploidy rate (m-ER) per patient and live birth rate (LBR) after vitrified-warmed euploid single embryo transfer (SET)? DESIGN: Observational study conducted between April 2013 and March 2020 at a private IVF clinic, involving 1811 Caucasian women undergoing trophectoderm biopsy and comprehensive chromosome testing. The outcomes of 1125 first vitrified-warmed euploid SET were also analysed. Patients were clustered as normal weight (BMI 18.5-25; n = 1392 performing 859 SET), underweight (BMI <18.5; n = 160 performing 112 SET) and overweight (BMI >25; n = 259 performing 154 SET). m-ER per patient was the primary outcome. The secondary outcomes were all clinical outcomes per euploid SET. All data were adjusted for confounders through regression analyses. RESULTS: The m-ER per patient decreases as maternal BMI increases from 17 up to 22-23 before reaching a plateau. A linear regression adjusted for maternal age confirmed this moderate association (unstandardized coefficient B: -0.6%, 95% confidence interval [CI]: -1.1 to -0.1%, P = 0.02). All clinical outcomes were similar between normal weight and underweight women. Overweight women, instead, showed higher miscarriage rate per clinical pregnancy (n = 20/75, 26.7% versus n = 67/461, 14.5%; odds ratio [OR] adjusted for blastocyst quality and day of full blastulation: 2.0, 95% CI: 1.1-3.6, P = 0.01) and lower LBR per SET (n = 55/154, 35.7% versus n = 388/859, 45.2%; OR adjusted for blastocyst quality and day of full blastulation: 0.67, 95% CI: 0.46-0.96, P = 0.03). CONCLUSION: These data indicate a need for future research on more sensitive metrics to assess body fat mass and distribution, as well as on the mechanisms leading to lipotoxicity, thereby impairing embryo competence and/or endometrial receptivity. Overweight women should be informed of their higher risk for miscarriage and, whenever possible, encouraged to lose weight, especially before transfer.

Looking past the appearance: a comprehensive description of the clinical contribution of poor-quality blastocysts to increase live birth rates during cycles with aneuploidy testing.

STUDY QUESTION: Which are the clinical benefits and risks of including poor-quality blastocysts (PQBs) in the cohort of biopsied embryos during a cycle with preimplantation genetic testing for aneuploidies (PGT-A)? SUMMARY ANSWER: PQBs show a worse prognosis with respect to sibling non-PQBs, but their clinical use allows an overall 2.6% increase in the number of live births (LBs) achievable after PGT-A. WHAT IS KNOWN ALREADY: PQBs (

Associations of blastocyst features, trophectoderm biopsy and other laboratory practice with post-warming behavior and implantation.

STUDY QUESTION: Are trophectoderm biopsy or other pre-vitrification features or laboratory practices associated with differences in blastocyst post-warming behavior (degeneration, re-expansion and live birth after single embryo transfer (SET))? SUMMARY ANSWER: Blastocyst morphology, day of full development and artificial shrinkage (either laser-assisted or biopsy-induced) are the pre-vitrification parameters/practices most strongly associated with post-warming behavior and implantation potential while there was no association with trophectoderm biopsy. WHAT IS KNOWN ALREADY: Since the introduction of vitrification, the adoption of cycle segmentation, freeze-all and SET policies, as well of trophectoderm biopsy-based aneuploidy testing (i.e. pre-implantation genetic testing for aneuploidies (PGT-A)), the number of blastocysts vitrified worldwide has increased greatly. Previous studies already defined generally high blastocyst cryo-survival rates after vitrification-warming (>95%), along with a positive correlation between blastocyst re-expansion and morphology with implantation. Additionally, artificial shrinkage has been outlined as a potentially beneficial procedure, while the association between embryo cryo-survival and trophectoderm biopsy is still unclear. STUDY DESIGN, SIZE, DURATION: Cohort study conducted at two IVF centers (1 and 2). A total of 2129 consecutive SETs using vitrified-warmed blastocysts in either non-PGT or PGT-A cycles between June 2016 and August 2017 were included. A freeze-all strategy was in place and three main pre-vitrification practices were used: (i) no biopsy and no artificial shrinkage (Clinic 1); (ii) trophectoderm biopsy and vitrification of collapsed blastocyst within 30 min (Clinics 1 and 2); and (iii) no biopsy but laser-assisted artificial shrinkage (Clinic 2). The primary outcome was the blastocyst degeneration rate. Overall, 2108 surviving blastocysts were graded at 1.5 h after warming for degeneration (absent or partial) and re-expansion (full, partial or absent) grades and post-warming morphological quality. Logistic regression analyses were conducted to assess the association of any pre-vitrification feature with blastocyst post-warming behavior. The logistic regressions conducted upon live birth after either untested or euploid SET also included the post-warming characteristics. PARTICIPANTS/MATERIALS, SETTING, METHODS: Center 1 is a private IVF facility, while center 2 is the IVF facility of a University hospital. In non-PGT cycles, ICSI with blastocyst culture up to full-expansion and vitrification were performed. At center 1 the untested blastocysts were vitrified when still expanded, while at center 2 they underwent laser-assisted artificial shrinkage. In PGT-A cycles, in both clinics, trophectoderm biopsy (which involves laser-assisted shrinkage) was done without previous zona-opening on Day 3, and vitrification was performed within 30 min whilst the blastocyst remained collapsed. A qPCR-based chromosome analysis was conducted. Only SETs were performed (euploid-SET in case of PGT-A). Any cycle-, laboratory- and embryo-based feature which could impact blastocyst post-warming behavior was included in the analyses as putative confounder. MAIN RESULTS AND THE ROLE OF CHANCE: The overall degeneration rate was 1% (N = 21/2129). The results were consistent among different vitrification/warming operators or kits used, as well as any other IVF laboratory-related parameter. Blastocyst artificial shrinkage (either laser-assisted or biopsy-induced) involved a lower risk of degeneration after warming (odds ratio (OR) [95% CI] = 0.26 [0.09-0.79]). Conversely, both poor morphological quality pre-vitrification and taking 7 days to reach full blastulation resulted in a significantly higher risk (OR [95% CI] = 11.67 [3.42-39.83] and 4.43 [1.10-20.55], respectively). Importantly, trophectoderm biopsy did not show any association with blastocyst cryo-survival/degeneration. Overall 2.5% (N = 53/2108) blastocysts failed to re-expand post-warming. The only parameters significantly associated with no blastocyst re-expansion post-warming were average (OR [95% CI] = 4.96 [2.20-11.21]) or poor (OR [95% CI] = 19.54 [8.39-45.50]) morphological quality and taking 7 days to reach full blastulation (OR [95% CI] = 3.19 [1.23-8.29]), as well as prevention of spontaneous hatching pre-vitrification (OR [95% CI] = 0.10 [0.01-0.85]). The post-warming features of the survived blastocyst (i.e. degeneration and re-expansion scores and morphological quality) showed no significant association with vitrified blastocyst competence (i.e. live birth) when corrected for pre-vitrification ones (i.e. morphological quality, day of full development and, for untested SET, maternal age at oocyte retrieval). Of note, poor-quality blastocysts pre-vitrification showed a high overall cryo-survival rate post-warming 92.8% (N = 116/125), but the live birth rates were only 2.1% (N = 1/48) and 7.3% (N = 5/68) after untested and euploid SET, respectively. LIMITATIONS, REASONS FOR CAUTION: This study is not randomized and the populations of patients undergoing either non-PGT or PGT-A cycles were different. Centers 1 and 2 adopted different pre-vitrification practices for non-biopsied blastocysts, according to their own laboratory policy. To this regard, multivariate logistic regression analyses were conducted for all outcomes under investigation. WIDER IMPLICATIONS OF THE FINDINGS: Pre-vitrification features may be used to assist selection of competent embryos, moreover, these results allay concern that trophectoderm biopsy might be associated with impaired blastocyst quality or competence after vitrification/warming. STUDY FUNDING/COMPETING INTEREST(S): None. TRIAL REGISTRATION NUMBER: None.

Biochemical pregnancy loss after frozen embryo transfer seems independent of embryo developmental stage and chromosomal status.

RESEARCH QUESTION: Biochemical pregnancy loss (BPL), defined as serum beta-human chorionic gonadotropin levels ≥50 IU/l in at least two pregnancy tests, not associated with any ultrasonographical evidence of pregnancy, is often attributed to chromosomal abnormalities; however, no hard evidence exists to support this hypothesis. Are any IVF cycle parameters associated with the occurrence of a BPL? DESIGN: Retrospective study aimed at evaluating the effect of embryo developmental stage at transfer and chromosomal assessment on the BPL rate in IVF after frozen embryo transfer (FET). Specifically, 641 FET of 1179 cleavage stage untested embryos (Group A), 1021 FET of 1259 untested blastocyst stage embryos (Group B), and 789 blastocyst stage FET of 803 euploid embryos (Group C) were performed in a 6-year period. Only FET were evaluated to avoid a potential effect of ovarian stimulation on endometrial receptivity. RESULTS: The BPL rates were similar (n = 30/217, 13.8% in Group A; n = 37/412, 9.0% in Group B; n = 42/433, 9.7% in Group C). Neither embryo developmental stage at FET nor chromosomal assessment showed a correlation with BPL. Furthermore, logistic regression analyses did not show any association between BPL and patient, cycle and/or transfer characteristics. CONCLUSIONS: BPL seems independent of the embryo's developmental stage, the use of trophectoderm biopsy and the chromosomal constitution at FET. Similar BPL rates after transferring euploid blastocysts compared with both untested cleavage and blastocyst stage embryos suggest investigating the role of endometrial and other embryonic factors putatively involved in the process of implantation.

Biomechanical forces and signals operating in the ovary during folliculogenesis and their dysregulation: implications for fertility.

BACKGROUND: Folliculogenesis occurs in the highly dynamic environment of the ovary. Follicle cyclic recruitment, neo-angiogenesis, spatial displacement, follicle atresia and ovulation stand out as major events resulting from the interplay between mechanical forces and molecular signals. Morphological and functional changes to the growing follicle and to the surrounding tissue are required to produce oocytes capable of supporting preimplantation development to the blastocyst stage. OBJECTIVE AND RATIONALE: This review will summarize the ovarian morphological and functional context that contributes to follicle recruitment, growth and ovulation, as well as to the acquisition of oocyte developmental competence. We will describe the changes occurring during folliculogenesis to the ovarian extracellular matrix (ECM) and to the vasculature, their influence on the mechanical properties of the ovarian tissue, and, in turn, their influence on the regulation of signal transduction. Also, we will outline how their dysregulation might be associated with pathologies such as polycystic ovary syndrome (PCOS), endometriosis or premature ovarian insufficiency (POI). Finally, for each of these three pathologies, we will highlight therapeutic strategies attempting to correct the altered biomechanical context in order to restore fertility. SEARCH METHODS: For each area discussed, a systematic bibliographical search was performed, without temporal limits, using PubMed Central, Web of Science and Scopus search engines employing the keywords extracellular matrix, mechanobiology, biomechanics, vasculature, angiogenesis or signalling pathway in combination with: ovary, oogenesis, oocyte, folliculogenesis, ovarian follicle, theca, granulosa, cumulus, follicular fluid, corpus luteum, meiosis, oocyte developmental competence, preimplantation, polycystic ovary syndrome, premature ovarian insufficiency or endometriosis. OUTCOMES: Through search engines queries, we yielded a total of 37 368 papers that were further selected based on our focus on mammals and, specifically, on rodents, bovine, equine, ovine, primates and human, and also were trimmed around each specific topic of the review. After the elimination of duplicates, this selection process resulted in 628 papers, of which 287 were cited in the manuscript. Among these, 89.2% were published in the past 22 years, while the remaining 8.0%, 2.4% or 0.3% were published during the 1990s, 1980s or before, respectively. During folliculogenesis, changes occur to the ovarian ECM composition and organization that, together with vasculature modelling around the growing follicle, are aimed to sustain its recruitment and growth, and the maturation of the enclosed oocyte. These events define the scenario in which mechanical forces are key to the regulation of cascades of molecular signals. Alterations to this context determine impaired folliculogenesis and decreased oocyte developmental potential, as observed in pathological conditions which are causes of infertility, such as PCOS, endometriosis or POI. WIDER IMPLICATIONS: The knowledge of these mechanisms and the rules that govern them lay a sound basis to explain how follicles recruitment and growth are modulated, and stimulate insights to develop, in clinical practice, strategies to improve follicular recruitment and oocyte competence, particularly for pathologies like PCOS, endometriosis and POI.

Embryonic cell-free DNA versus trophectoderm biopsy for aneuploidy testing: concordance rate and clinical implications.

OBJECTIVE: To study whether embryonic cell-free DNA (cfDNA) in spent blastocyst media is representative of the chromosomal constitution of a blastocyst. DESIGN: Pilot prospective blinded study. SETTING: In vitro fertilization center and genetics laboratory. PATIENT(S): A total of 115 trophectoderm (TE) biopsies and spent blastocyst media (SBM) from 46 patients with ages ranging from 32 to 46 years, whose indications for preimplantation genetic testing of aneuploidy (PGT-A) were advanced maternal age, recurrent miscarriage, or recurrent implantation failure. INTERVENTIONS(S): Spent blastocyst media collection and TE biopsy. MAIN OUTCOME MEASURE(S): Concordance rates, sensitivity, and specificity between TE biopsies and SBM. Clinical outcomes in cases with euploid TE biopsies and euploid SBM compared with cases with euploid TE and aneuploid SBM. RESULT(S): In general, the total concordance rate for ploidy and sex was 78.7%, and sensitivity and specificity were 94.5% and 71.7%, respectively. A significant increase for all parameters was observed for day 6/7 samples compared with day 5 samples, with day 6/7 samples showing total concordance for ploidy and sex of 84%, and sensitivity and specificity of 95.2% and 82.1%, respectively. Ongoing implantation rates in euploid TE/euploid SBM showed a threefold increase compared with euploid TE/aneuploid SBM (52.9% vs. 16.7%, respectively), without reaching significant differences. Interestingly, no miscarriages were observed when TE and SBM were euploidy concordant. CONCLUSION(S): These results offer a better understanding of the dynamics of cfDNA during embryo development and despite more basic research being needed, they are reassuring to consider in the future this noninvasive approach as an alternative to TE biopsy for PGT-A.