Cytoplasmic strings in human blastocysts: hypotheses of their role and implications for embryo selection.

STUDY QUESTION: What are the implications of the presence cytoplasmic strings (Cyt-S) and their quantity and dynamics for the pre-implantation development of human blastocysts? SUMMARY ANSWER: Cyt-S are common in human embryos and are associated with faster blastocyst development, larger expansion, and better morphological quality. WHAT IS KNOWN ALREADY: Cyt-S are dynamic cellular projections connecting inner cell mass and trophectoderm (TE) cells, that can be observed during blastocyst expansion. Their prevalence in human embryos has been estimated to be between 44% and 93%. Data relevant to their clinical implications and role in development are lacking, limited, or controversial. STUDY DESIGN, SIZE, DURATION: Retrospective study conducted at a single IVF center between May 2013 and November 2014 and involving 124 pre-implantation genetic testing for aneuploidy cycles in a time-lapse incubator with ≥1 blastocyst biopsied and vitrified (N = 370 embryos assessed). These cycles resulted in 87 vitrified-warmed single-euploid blastocyst transfers. PARTICIPANTS/MATERIALS, SETTING, METHODS: ICSI, continuous blastocyst culture (Days 5-7), TE biopsy of fully expanded blastocysts without Day 3 zona pellucida drilling, qPCR to assess uniform full-chromosome aneuploidies, and vitrification were all performed. Only vitrified-warmed euploid single-embryo-transfers were conducted. Blastocyst morphological quality was defined according to Gardner's criteria. The AI-based software CHLOE™ (Fairtility) automatically registered timings from time of starting blastulation (tSB) to biopsy (t-biopsy, i.e. blastocyst full-expansion) as hours-post-insemination (hpi), embryo area (including zona pellucida in µm2), and spontaneous blastocyst collapses. One senior embryologist manually annotated Cyt-S presence, quantity, timings, and type (thick cell-to-cell connections and/or threads). All significant associations were confirmed through regression analyses. All couples', cycles', and embryos' main features were also tested for associations with Cyt-S presence, quantity, and dynamics. MAIN RESULTS AND THE ROLE OF CHANCE: About 94.3% of the patients (N = 117/124) had ≥1 embryo with Cyt-S. Out of a total of 370 blastocysts, 55 degenerated between blastulation and full-expansion (N = 55/370, 14.9%). The degeneration rate among embryos with ≥1 Cyt-S was 10.8% (N = 33/304), significantly lower than that of embryos without Cyt-S (33.3%, N = 22/66, P < 0.01). Of the remaining 315 viable blastocysts analyzed, 86% (N = 271/315; P < 0.01) had ≥1 Cyt-S, on average 3.5 ± 2.1 per embryo ranging 1-13. The first Cyt-S per viable embryo appeared at 115.3 ± 12.5 hpi (85.7-157.7), corresponding to 10.5 ± 5.8 h (0.5-31) after tSB. Overall, we analyzed 937 Cyt-S showing a mean duration of 3.8 ± 2.7 h (0.3-20.9). Cyt-S were mostly threads (N = 508/937, 54.2%) or thick cell-to-cell connections becoming threads (N = 382/937, 40.8%) than thick bridges (N = 47/937, 5.0%). The presence and quantity of Cyt-S were significantly associated with developmentally faster (on average 6-12 h faster) and more expanded (on average 2700 µm2-larger blastocyst's area at t-biopsy) embryos. Also, the presence and duration of Cyt-S were associated with better morphology. Lastly, while euploidy rates were comparable between blastocysts with and without Cyt-S, all euploid blastocysts transferred from the latter group failed to implant (N = 10). LIMITATIONS, REASONS FOR CAUTION: Cyt-S presence and dynamics were assessed manually on seven focal planes from video frames recorded every 15 min. The patients included were mostly of advanced maternal age. Only associations could be reported, but no causations/consequences. Lastly, larger datasets are required to better assess Cyt-S associations with clinical outcomes. WIDER IMPLICATIONS OF THE FINDINGS: Cyt-S are common during human blastocyst expansion, suggesting their physiological implication in this process. Their presence, quantity and dynamics mirror embryo viability, and morphological quality, yet their role is still unknown. Future basic science studies are encouraged to finally describe Cyt-S molecular nature and biophysical properties, and Artificial Intelligence tools should aid these studies by incorporating Cyt-S assessment. STUDY FUNDING/COMPETING INTEREST(S): None. TRIAL REGISTRATION NUMBER: N/A.

Discard or not discard, that is the question: an international survey across 117 embryologists on the clinical management of borderline quality blastocysts.

STUDY QUESTION: Do embryologists from different European countries agree on embryo disposition decisions ('use' or 'discard') about Day 7 (>144 h post-insemination) and/or low-quality blastocysts (LQB;

Cryostorage management of reproductive cells and tissues in ART: status, needs, opportunities and potential new challenges.

Among the wide range of procedures performed by clinical embryologists, the cryopreservation of reproductive cells and tissues represents a fundamental task in the daily routine. Indeed, cryopreservation procedures can be considered a subspecialty of medically assisted reproductive technology (ART), having the same relevance as sperm injection or embryo biopsy for preimplantation genetic testing. However, although a great deal of care has been devoted to optimizing cryopreservation protocols, the same energy has only recently been spent on developing and implementing strategies for the safe and reliable storage and transport of reproductive specimens. Herein, we have summarized the content of the available guidelines, the risks, the needs and the future perspectives regarding the management of cryopreservation biorepositories used in ART.

Humidified atmosphere in a time-lapse embryo culture system does not improve ongoing pregnancy rate: a retrospective propensity score model study derived from 496 first ICSI cycles.

PURPOSE: To investigate whether high relative humidity conditions (HC), when using a time-lapse system (TLS) with sequential culture media, are beneficial to embryo culture, improving ongoing pregnancy rates. METHODS: We included patients undergoing their first ICSI cycle treatment from April 2021 to May 2022. Patients assigned to dry conditions (DC) or HC were 278 and 218, respectively. We used a GERI TLS, three chambers configured in humidity conditions and three in dry conditions. The effect of HC on ongoing pregnancy rate was assessed by the propensity matched sample, to reduce potential differences between women undergoing either HC or DC and reduce biased estimation of treatment effect. RESULT: After adjusting for several confounding variables and applying the propensity score (PS), no significant differences were observed in the rates of normal (2PN) and abnormal (1PN and 3PN) fertilization, blastulation, top-quality blastocysts, frozen blastocysts, ongoing pregnancies, and miscarriages. The 2-cell (t2) and 4-cell (t4) stages and cell divisions between such stages occurred earlier and were more synchronous in the in DC. CONCLUSION: These results suggest that HC conditions do not improve the rate of ongoing pregnancy and several embryological outcomes, under the conditions used in this study based on a time-lapse system and sequential culture with day 3 medium change-over.

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.

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.

Blastulation rates of sibling oocytes in two IVF culture media: an evidence-based workflow to implement newly commercialized products.

RESEARCH QUESTION: An evidence-based novel commercially available continuous IVF culture medium in compliance with an efficient quality-management system is proposed. DESIGN: Non-interventional study on sibling oocytes. Intracytoplasmic sperm injection cycles among women aged 42 years or younger that used ejaculated spermatozoa and retrieved four to eight oocytes were included. Sibling oocytes were randomized for culture in the novel Geri-medium or continuous single culture medium (CSCM). Primary outcome measure was blastulation rate per cohort of inseminated oocytes; 1182 oocytes were required to outline down to a 7% difference (power = 80%). RESULTS: A total of 181 cohorts of sibling oocytes were included. Geri-medium (n = 631 oocytes) and CSCM (n = 643 oocytes) resulted in similar blastulation rates (mean ± SD: 42.8% ± 30.1% versus 43.1% ± 29.0%; Wilcoxon signed rank test = 0.77). Blastocysts cultured in the former (n = 275 versus n = 277) showed longer timings during preimplantation development (P < 0.01) and were poorer quality (26% versus 18%; P = 0.03). Euploidy rate was no different in cycles that underwent preimplantation genetic testing for aneuploidy (n = 113) (117/237 [49%] versus 117/249 blastocysts [47%]; P = 0.6). Ongoing implantation rate was comparable in the study arms after euploid (29/47 [63%] versus 14/ 34 [41%]; P = 0.1) or untested (12/31 [39%] versus 7/18 [39%]; P = 0.3) transfers. CONCLUSION: Blastulation rate among cohorts of sibling oocytes cultured in the same incubator is a fast, reliable and comprehensive performance indicator to validate novel commercially available culture medium. The media tested were considered similarly efficient. The differences in blastocyst morphology and developmental timings warrant further investigation, although euploidy and ongoing implantation rates were similar.

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.

The effect of ICSI-related procedural timings and operators on the outcome.

STUDY QUESTION: Do the ICSI-related procedural timings and operators affect the outcomes of an ART cycle? SUMMARY ANSWER: The ICSI-related timings and operators do not associate with the mean blastulation rate per cohort of inseminated oocytes and the cumulative delivery rate per concluded cycle, except for a mild association between the times from induction of ovulation to oocyte denudation and the former outcome. WHAT IS KNOWN ALREADY: In ART, specific timings, protocols and conditions must be complied with to preserve gamete developmental and reproductive competence during the required manipulations. ICSI represents a groundbreaking advancement that has been widely implemented. Nevertheless, the studies that examined the putative impact of ICSI-related procedural timings were mainly conducted in old-fashioned settings or in good prognosis patients. No report addressed issues like operators' skills and experience and uncertainties exist dealing with the effect of cumulus cells in the pre-incubation period in vitro before ICSI. However, all this information is crucial to efficiently plan the daily routine of an IVF lab, fill the existing gaps of knowledge and define proper key performance indicators. STUDY DESIGN, SIZE, DURATION: Observational study conducted at a private IVF clinic (January 2016 to January 2018). We included all consecutive ICSI procedures (n = 1084 infertile couples undergoing 1444 cycles with or without preimplantation genetic testing (PGT); mean ± SD maternal age: 38.1 ± 4.0 years) with fresh autologous oocytes (n = 7999 oocytes, 5.5 ± 3.2 per treatment) inseminated with fresh non-donor ejaculated sperm. All operators and critical procedural timings (induction of ovulation to oocyte denudation, denudation and ICSI) were automatically recorded through an electronic witnessing system. The primary outcome measure was the cumulative delivery rate among both non-PGT and PGT-concluded cycles (i.e. delivery achieved or no supernumerary cryopreserved blastocyst available). The secondary outcome measure was the mean blastulation rate per cohort of inseminated oocytes. All confounders were registered and included in generalized linear models and multivariate logistic regression analyses. PARTICIPANTS/MATERIALS, SETTING, METHODS: Fourteen and 12 operators were involved in denudation and ICSI procedures, respectively. Denudation was performed after 4.1 ± 1.2 h (2-7) of pre-incubation in vitro after oocyte retrieval, and ICSI was started immediately after. Beyond procedural timings and operators, all the putative confounders (patients' and cycles' characteristics) on the primary and/or secondary outcomes were systematically registered and included in the statistical analyses. MAIN RESULTS AND THE ROLE OF CHANCE: The mean time from induction of ovulation to oocyte denudation was 39.3 ± 1.3 h. The mean procedural timings for denudation and ICSI were 8.1 ± 3.8 and 12.6 ± 6.4 min; both these variables were significantly dependent on the number of inseminated oocytes and the operators' skills and experience. The overall mean blastulation rate per cohort of inseminated oocytes was 34.0 ± 27.9%. This outcome was significantly associated with the time from induction of ovulation to oocyte denudation (mean blastulation rate stable in the time interval 38-42 h, but significantly higher for timings <38 h), maternal age (the mean blastulation rate drops especially beyond the age of 40 years) and categorized sperm concentration (highest mean blastulation rate for sperm concentrations ≥15 mil/ml and lowest for cryptozoospermic patients) through a generalized linear model that showed an adjusted r2 = 0.053 (P < 0.01). No association was found for denudation and ICSI timings and operators. Lastly, when adjusted for maternal age and number of inseminated oocytes, both ICSI-related procedural timings and operators did not associate with the cumulative delivery rate among both non-PGT- or PGT-concluded cycles. LIMITATIONS, REASONS FOR CAUTION: This is a single private IVF center study. Its reproducibility should be assessed in different laboratory conditions, with different protocols and in the hands of different operators. Moreover, specific studies are warranted to address the beneficial/detrimental effect of the other putative confounders under investigation (e.g. kind of ovulation trigger, culture media, incubator, etc.). WIDER IMPLICATIONS OF THE FINDINGS: Proactive communication between the embryologists and the clinicians might contribute to a reasoned and more efficient organization of the daily workload and increase the mean blastulation rate, especially when poor prognosis couples (advanced maternal age, reduced sperm count and/or ovarian reserve) are treated. STUDY FUNDING/COMPETING INTEREST(S): No funding. The authors declare no conflict of interest related to the present study.

Definition of a clinical strategy to enhance the efficacy, efficiency and safety of egg donation cycles with imported vitrified oocytes.

STUDY QUESTION: Which is the most suitable clinical strategy in egg donation IVF cycles conducted with imported donated vitrified oocytes? SUMMARY ANSWER: The importation, and allocation, of at least eight vitrified eggs per couple during an egg donation cycle is associated with a high cumulative live birth delivery rate per cycle, as well as the confident adoption of a single blastocyst transfer strategy to minimize the risk of multiple pregnancies. WHAT IS KNOWN ALREADY: IVF using donor eggs is commonly used worldwide to treat women who are unable to conceive with their own oocytes. In 2014, the Constitutional Court (n.162/2014) gave permission for gamete donation to be allowed for ART in Italy. Initially recommended as a therapeutic approach for premature ovarian insufficiency, the use of donated oocytes has become more and more common. In countries such as Italy, fresh oocyte donation is theoretically possible, but practically impossible due to the lack of donors. In fact, the Italian law does not allow reimbursement to the young women, who can only voluntarily donate their eggs. Therefore, Italian IVF centers have established several collaborations with international oocyte cryo-banks. The most popular workflow involves the importation of donated oocytes that have been vitrified. However, recent evidence has questioned the overall efficacy of such an approach. This is because detrimental effects arising from oocyte vitrification and warming might reduce the number of eggs available for insemination, with a consequential reduction in the achievable live birth rate per cycle. STUDY DESIGN, SIZE, DURATION: This was a longitudinal cohort study, conducted between October 2015 and December 2018 at two private IVF centers. Overall, 273 couples were treated (mean maternal age: 42.5 ± 3.5 years, range: 31-50 years; mean donor age: 25.7 ± 4.2, 20-35 years) with oocytes purchased from three different Spanish egg banks. PARTICIPANTS/MATERIALS, SETTING, METHODS: We performed an overall analysis, as well as several sub-analyses clustering the data according to the year of treatment (2015-2016, 2017 or 2018), the number of warmed (6, 7, 8 or 9) and surviving oocytes (≤4, 5, 6, 7, 8 or 9) and the cycle strategy adopted (cleavage stage embryo transfer and vitrification, cleavage stage embryo transfer and blastocyst vitrification, blastocyst stage embryo transfer and vitrification). This study aimed to create a workflow to maximize IVF efficacy, efficiency, and safety, during egg donation cycles with imported vitrified oocytes. The primary outcome was the cumulative live birth delivery rate among completed cycles (i.e. cycles where at least a delivery of a live birth was achieved, or no embryo was produced/left to transfer). All cycles, along with their embryological, obstetric and neonatal outcomes, were registered and inspected. MAIN RESULTS AND THE ROLE OF CHANCE: The survival rate after warming was 86 ± 16%. When 6, 7, 8 and 9 oocytes were warmed, 94, 100, 72 and 70% of cycles were completed, resulting in 35, 44, 69 and 59% cumulative live birth delivery rates per completed cycle, respectively. When ≤4, 5, 6, 7, 8 and 9 oocytes survived, 98, 94, 85, 84, 66 and 68% of cycles were completed, resulting in 16, 46, 50, 61, 76 and 60% cumulative live birth delivery rates per completed cycle, respectively. When correcting for donor age, and oocyte bank, in a multivariate logistic regression analysis, warming eight to nine oocytes resulted in an odds ratio (OR) of 2.5 (95% CI: 1.07-6.03, P = 0.03) for the cumulative live birth delivery rate per completed cycle with respect to six to seven oocytes. Similarly, when seven to nine oocytes survived warming, the OR was 2.7 (95% CI: 1.28-5.71, P < 0.01) with respect to ≤6 oocytes. When cleavage stage embryos were transferred, a single embryo transfer strategy was adopted in 17% of cases (N = 28/162); the live birth delivery rate per transfer was 26% (n = 43/162), but among the pregnancies to term, 28% involved twins (n = 12/43). Conversely, when blastocysts were transferred, a single embryo transfer strategy was adopted in 96% of cases (n = 224/234) with a 30% live birth delivery rate per transfer (N = 70/234), and the pregnancies to term were all singleton (n = 70/70). During the study period, 125 babies were born from 113 patients. When comparing the obstetric outcomes for the cleavage and blastocyst stage transfer strategies, the only significant difference was the prevalence of low birthweight: 34 versus 5%, respectively (P < 0.01). However, several significant differences were identified when comparing singleton with twin pregnancies; in fact, the latter resulted in a generally lower birthweight (mean ± SD: 3048 ± 566 g versus 2271 ± 247 g, P < 0.01), a significantly shorter gestation (38 ± 2 versus 36 ± 2 weeks, P < 0.01), solely Caesarean sections (72 versus 100%, P = 0.02), a higher prevalence of low birthweight (8 versus 86%, P < 0.01), small newborns for gestational age (24 versus 57%, P = 0.02) and preterm births (25 versus 86%, P < 0.01). LIMITATIONS, REASONS FOR CAUTION: This retrospective study should now be confirmed across several IVF centers and with a greater sample size in order to improve the accuracy of the sub-analyses. WIDER IMPLICATIONS OF THE FINDINGS: Single blastocyst transfer is the most suitable approach to achieve high success rates per procedure, thereby also limiting the obstetric complications that arise from twin pregnancies in oocyte donation programs. In this regard, the larger the cohort of imported donated vitrified oocytes, the more efficient the management of each cycle. STUDY FUNDING/COMPETING INTEREST(S): None. TRIAL REGISTRATION NUMBER: None.

Assessment and management of the risk of SARS-CoV-2 infection in an IVF laboratory.

RESEARCH QUESTION: The study set out to identify corrective measures aimed at reducing the risk of aerosol-mediated viral infection within an IVF laboratory. DESIGN: A failure modes and effect analysis (FMEA) was conducted by a multidisciplinary IVF team. A schematic representation of new protocols and procedures adopted during COVID-19 emergency has been defined, including directives about the behaviour to adopt when entering the clinic and the laboratory, in case of face-to-face contact with patients and between staff members. In addition, the risk of cross-contamination between samples belonging to different patients during cell handling and manipulation has been evaluated. Potential failure modes for each phase of the emergency have been analysed, focusing on possible sources of error. Risk priority numbers have been calculated as products of Occurrence × Severity × Detection scores. RESULTS: Except for cell-cell contamination, which was considered highly unlikely, failure modes during patient-staff, staff-staff and staff-cell interactions were estimated as carrrying a moderate to high risk of infection. The main corrective measures entailed precautionary logistic measures, the implementation of additional personal protective equipment and changes in the IVF laboratory procedures and scheduling of the daily routine. Some procedures were also revised, aiming to increase staff's awareness and caution. CONCLUSIONS: Standard laboratory protocols are insufficient to face a virus whose transmission is aerosol mediated. The measures outlined in this FMEA should thus be considered not only for facing this pandemic, but also for the future to promptly manage any aerosol-mediated virus infection, whose impact on the management of an IVF laboratory might be less severe than COVID-19 although not completely negligible.

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 (

A brief history of oocyte cryopreservation: Arguments and facts.

The term "cryopreservation" refers to the process of cooling cells and tissues and storing them at subzero temperatures in order to stop all biological activity and preserve their viability and physiological competences for future use. Cooling to subzero temperatures is not a physiological condition for human cells; this is probably due to the high content of water in the living matter, whose conversion to ice crystals may be associated with severe and irreversible damage. Among reproductive cells and tissues, metaphase II oocytes are notably vulnerable to cryopreservation, mainly because of their large size, low surface area to volume ratio, relatively high water content and presence of the meiotic spindle. As human biological systems lack efficient internal defense mechanisms against chilling injuries, it is of the utmost importance to supply adequate external support, in terms of cryoprotectant additives, appropriate cooling/warming rates, and suitable long-term storage. Over the years, scientists have proposed different cryopreservation strategies in the effort to achieve an optimized recipe ensuring cell survival and, at the same time, maintenance of the physiological functions and abilities necessary to continue life. However, despite the first success obtained in the 1980s with frozen oocytes, it was not until recently that notable improvements in the cryopreservation technique, thanks to the advent of vitrification, allowed a breakthrough of this fine procedure.

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.

Consistent and reproducible outcomes of blastocyst biopsy and aneuploidy screening across different biopsy practitioners: a multicentre study involving 2586 embryo biopsies.

STUDY QUESTION: Is blastocyst biopsy and quantitative real-time PCR based comprehensive chromosome screening a consistent and reproducible approach across different biopsy practitioners? SUMMARY ANSWER: The blastocyst biopsy approach provides highly consistent and reproducible laboratory and clinical outcomes across multiple practitioners from different IVF centres when all of the embryologists received identical training and use similar equipment. WHAT IS KNOWN ALREADY: Recently there has been a trend towards trophectoderm (TE) biopsy in preimplantation genetic screening (PGS)/preimplantation genetic diagnosis (PGD) programmes. However, there is still a lack of knowledge about the reproducibility that can be obtained from multiple biopsy practitioners in different IVF centres in relation also to blastocysts of different morphology. Although it has been demonstrated that biopsy at the blastocyst stage has no impact on embryo viability, it remains a possibility that less experienced individual biopsy practitioners or laboratories performing TE biopsy may affect certain outcomes. We investigated whether TE biopsy practitioners can have an impact on the quality of the genetic test and the subsequent clinical outcomes. STUDY DESIGN, SIZE, DURATION: This longitudinal cohort study, between April 2013 and December 2014, involved 2586 consecutive blastocyst biopsies performed at three different IVF centres and the analysis of 494 single frozen euploid embryo transfer cycles (FEET). PARTICIPANTS/MATERIALS, SETTING, METHODS: Seven biopsy practitioners performed the blastocyst biopsies in the study period and quantitative PCR was used for comprehensive chromosome screening (CCS). The same practitioner performed both the biopsy and tubing procedures for each blastocyst they biopsied. To investigate the quality of the biopsied samples, the diagnostic rate, sample-specific concurrence and the cell number retrieved in the biopsy were evaluated for each biopsy operator. Clinical outcomes following FEET cycles were stratified by biopsy operator and compared. Cellularity of the biopsy sample was also correlated with clinical outcomes. MAIN RESULTS AND THE ROLE OF CHANCE: The seven practitioners performed 2586 biopsies, five in centre IVF-1 and one in each of the other two IVF centres (IVF-2 and IVF-3). Overall, 2437 out of 2586 (94.2%) blastocyst biopsies resulted in a conclusive diagnosis, 119 (4.6%) showed a nonconcurrent result and 30 (1.2%) failed to amplify, suggesting the absence of TE cells in the test tube or presence of degenerated/lysed cells only. Among the samples producing a conclusive diagnosis, a mean concurrence value of 0.253 (95% CI = 0.250-0.257) was observed. Logistic regression analysis adjusted for confounding factors showed no differences in the diagnosis rate and in the concurrence of the genetic analysis between different biopsy practitioners. An overall mean number of 7.32 cells (95% CI = 6.82-7.81; range 2-15) were predicted from all biopsies. Higher cellularity was significantly associated with a better quality of the CCS diagnosis (P < 0.01) and with the conclusive diagnosis rate, with nonconcurrent samples showing significantly lower numbers of cells (2.1; 95% CI=1.5-2.7) compared with samples resulting in a conclusive diagnosis (mean cells number 7.5; 95% CI = 7.1-7.9, P < 0.01). However, no differences were recorded between different biopsy practitioners regarding cellularity of the biopsy. Finally, logistic analysis showed no impact of the biopsy practitioners on the observed ongoing rates of implantation, biochemical pregnancy loss and miscarriage after the FEET cycles. LIMITATIONS, REASONS FOR CAUTION: These data come from a restricted set of laboratories where all of the embryologists received identical training and use identical equipment. A single TE biopsy method and CCS technology was used and these data particularly apply to PGS programmes using blastocyst biopsy without zona opening at the cleavage stage and using qPCR-based CCS. To make firm conclusions on the potential impact of biopsy on biochemical pregnancy loss and miscarriages according to practitioner and biopsy cellularity, a larger sample size is needed. WIDER IMPLICATIONS OF THE FINDINGS: We reported a very high consistency and reproducibility of the blastocyst biopsy approach coupled with qPCR-based CSS for both genetic and clinical outcomes across different practitioners working in different IVF centres when appropriate training is provided and when the same laboratory setting is used. These data are important considering the trend towards the use of blastocyst biopsy worldwide for PGD/PGS applications. STUDY FUNDING/COMPETING INTERESTS: None.

Failure mode and effects analysis of witnessing protocols for ensuring traceability during PGD/PGS cycles.

Preimplantation genetic diagnosis and aneuploidy testing (PGD/PGS) use is constantly growing in IVF, and embryo/biopsy traceability during the additional laboratory procedures needed is pivotal. An electronic witnessing system (EWS), which showed a significant value in decreasing mismatch occurrence and increasing detection possibilities during standard care IVF, still does not guarantee the same level of efficiency during PGD/PGS cycles. Specifically, EWS cannot follow single embryos throughout the procedure. This is however critical when an unambiguous diagnosis corresponds to each embryo. Failure Mode and Effects Analysis (FMEA) is a proactive method generally adopted to define tools ensuring safety along a procedure. Due to the implementation of a large quantitative PCR (qPCR)-based blastocyst stage PGD/PGS programme in our centre, and to evaluate the potential procedural risks, a FMEA was performed in September 2014. Forty-four failure modes were identified, among which six were given a moderate risk priority number (>15) (RPN; product of estimated occurrence, severity and detection). Specific corrective measures were then introduced and implemented, and a second evaluation performed six months later. The meticulous and careful application of such measures allowed the risks to be decreased along the whole protocol, by reducing their estimated occurrence and/or increasing detection possibilities.

Electronic witness system in IVF-patients perspective.

OBJECTIVE: The objective of this study is to evaluate patient concerns about in vitro fertilization (IVF) errors and electronic witness systems (EWS) satisfaction. DESIGN: The design of this study is a prospective single-center cohort study. SETTING: The setting of this study was located in the private IVF center. PATIENT(S): Four hundred eight infertile patients attending an IVF cycle at a GENERA center in Italy were equipped with an EWS. INTERVENTION(S): Although generally recognized as a very rare event in IVF, biological sample mix-up has been reported in the literature. For this reason, some IVF laboratories have introduced EWS with the aim to further reduce the risk of error during biological samples handling. Participating patients received a questionnaire developed through a Likert scale ranging from 1 to 6. MAIN OUTCOMES MEASURE(S): Patient concerns about sample mix-up without and with an EWS were assessed. RESULT(S): 90.4 % of patients expressed significant concerns relating to sample mix-up. The EWS reduced these concerns in 92.1 % of patients, 97.1 % of which were particularly satisfied with the electronic traceability of their gametes and embryos in the IVF laboratory. 97.1 % of patients felt highly comfortable with an IVF center equipped with an EWS. Female patients had a significantly higher appreciation of the EWS when compared to their male partners (p = 0.029). A significant mix-up event occurred in an Italian hospital during the study and patient's satisfaction increased significantly towards the use of the EWS after the event (p = 0.032). CONCLUSION(S): EWS, by sensibly reducing the risk for sample mix-up in IVF cycles, has been proved to be a trusted strategy from patient's perspective.

Reduction of multiple pregnancies in the advanced maternal age population after implementation of an elective single embryo transfer policy coupled with enhanced embryo selection: pre- and post-intervention study.

STUDY QUESTION: Is an elective single-embryo transfer (eSET) policy an efficient approach for women aged >35 years when embryo selection is enhanced via blastocyst culture and preimplantation genetic screening (PGS)? SUMMARY ANSWER: Elective SET coupled with enhanced embryo selection using PGS in women older than 35 years reduced the multiple pregnancy rates while maintaining the cumulative success rate of the IVF programme. WHAT IS KNOWN ALREADY: Multiple pregnancies mean an increased risk of premature birth and perinatal death and occur mainly in older patients when multiple embryos are transferred to increase the chance of pregnancy. A SET policy is usually recommended in cases of good prognosis patients, but no general consensus has been reached for SET application in the advanced maternal age (AMA) population, defined as women older than 35 years. Our objective was to evaluate the results in terms of efficacy, efficiency and safety of an eSET policy coupled with increased application of blastocyst culture and PGS for this population of patients in our IVF programme. STUDY DESIGN, SIZE, DURATION: In January 2013, a multidisciplinary intervention involving optimization of embryo selection procedure and introduction of an eSET policy in an AMA population of women was implemented. This is a retrospective 4-year (January 2010-December 2013) pre- and post-intervention analysis, including 1161 and 499 patients in the pre- and post-intervention period, respectively. The primary outcome measures were the cumulative delivery rate (DR) per oocyte retrieval cycle and multiple DR. PARTICIPANTS/MATERIALS, SETTING, METHODS: Surplus oocytes and/or embryos were vitrified during the entire study period. In the post-intervention period, all couples with good quality embryos and less than two previous implantation failures were offered eSET. Embryo selection was enhanced by blastocyst culture and PGS (blastocyst stage biopsy and 24-chromosomal screening). Elective SET was also applied in cryopreservation cycles. MAIN RESULTS AND THE ROLE OF CHANCE: Patient and cycle characteristics were similar in the pre- and post-intervention groups [mean (SD) female age: 39.6 ± 2.1 and 39.4 ± 2.2 years; range 36-44] as assessed by logistic regression. A total of 1609 versus 574 oocyte retrievals, 937 versus 350 embryo warming and 138 versus 27 oocyte warming cycles were performed in the pre- and post-intervention periods, respectively, resulting in 1854 and 508 embryo transfers, respectively. In the post-intervention period, 289 cycles were blastocyst stage with (n = 182) or without PGS (n = 107). A mean (SD) number of 2.9 ± 1.1 (range 1-4) and 1.4 ± 0.8 (range 1-3) embryos were transferred pre- and post-intervention, respectively (P < 0.01) and similar cumulative clinical pregnancy rates per transfer and per cycle were obtained: 26.8, 30.9% and 29.7, 26.3%, respectively. The total DR per oocyte retrieval cycle (21.0 and 20.4% pre- and post-intervention, respectively) defined as efficacy was not affected by the intervention [odds ratio (OR) = 0.8, 95% confidence interval (CI) = 0.7-1.1; P = 0.23]. However, a significantly increased live birth rate per transferred embryo (defined as efficiency) was observed in the post-intervention group 17.0 versus 10.6% (P < 0.01). Multiple DRs decreased from 21.0 in the preintervention to 6.8% in the post-intervention group (OR = 0.3. 95% CI = 0.1-0.7; P < 0.01). LIMITATIONS, REASONS FOR CAUTION: In this study, the suitability of SET was assessed in individual women on the basis of both clinical and embryological prognostic factors and was not standardized. For the described eSET strategy coupled with an enhanced embryo selection policy, an optimized culture system, cryopreservation and aneuploidy screening programme is necessary. WIDER IMPLICATIONS OF THE FINDINGS: Owing to the increased maternal morbidity and perinatal complications related to multiple pregnancies, it is recommended to extend the eSET policy to the AMA population. As shown in this study, enhanced embryo selection procedures might allow a reduction in the number of embryos transferred and the number of transfers to be performed without affecting the total efficacy of the treatment but increasing efficiency and safety. STUDY FUNDING/COMPETING INTERESTS: None. TRIAL REGISTRATION NUMBER: None.