P-773 Assessment of the putative impact of culture strategies, oocyte/embryo manipulations, and operators: a retrospective analysis of 3705 blastocyst culture cycles and 2604 single blastocyst transfers

Study question

Do the culture strategies, oocyte/embryo manipulations, and operators impact blastulation-rates per cohort of metaphase-II oocytes (BR per MII-oocytes) and/or live-birth-rates per single-embryo-transfer (LBR per SET)?

Summary answer

Undisturbed culture improved the BR per MII-oocytes, while culture drop volumes ≥80ml in the well-of-the-well system were associated with increased LBR per untested/euploid blastocyst SET.

What is known already

IVF lab performance is critical to achieve success in IVF. Yet, while a consensus exists on the main key-performance-indicators (KPIs), namely BR and LBR, and their inherent benchmark values, the strategies to fulfil them are still poorly standardized. The plasticity of human embryos along with the disparities in the patient populations might mask even largely different outcomes across clinics. Therefore, clear guidelines shall outline which procedures to standardize and carefully monitor in IVF laboratories. Here we investigated different embryo culture strategies, manipulations, and operators for their effect on BR and LBR per SET, adjusting the results for all main confounders.

Study design, size, duration

Retrospective analysis of 3705 cycles with ≥1 MII-oocyte and 2604 SETs (January2019-March2021). BR per MII-oocytes and LBR per SET were the main outcomes. Embryo-twinning was also assessed. The putative impact of culture strategies, manipulations, and operators’ expertise (0-5yr,6-11yr or > 12yr) was determined via regression analyses adjusted for possible confounders (autologous/donated oocytes, age, primary/secondary infertility and duration, sperm factor; for SET: also endometrial preparation, age at transfer, number of consecutive transfer, untested/euploid blastocyst, quality, and day).

Participants/materials, setting, methods

In donation cycles, only vitrified oocytes were used. In Preimplantation-Genetic-Testing (PGT) cycles, no assisted-hatching was performed and only euploid non-mosaic vitrified-warmed blastocysts were transferred. The culture strategies assessed were undisturbed (Embryoscope, Geri and Embryoscope-plus)/disturbed (KSystems), volume and approach (drops ≤30ml with single-culture or ≥ 80ml with well-of-the-well approaches), humidified/non-humidified atmosphere and media refreshed/not-refreshed. The manipulations assessed were oocyte/blastocyst vitrification (performed/not-performed), oocyte retrieval and denudation performed with oil overlay (yes/not), laser-assisted artificial-shrinkage (performed/not-performed), trophectoderm biopsy (performed/not-performed).

Main results and the role of chance

The only confounders on BR per MII-oocytes (overall:39.1±26.6%) were sperm factor and oocyte age. The linear regressions showed benefits for humidified atmosphere (unstandardized B-coefficient:+2.9%, p = 0.01), manipulations with oil overlay (+3.9%, p = 0.03) and drops≥80ml with a well-of-the-well approach (+4.3%, p < 0.01). However, only the positive effect of undisturbed incubators was significant when adjusting for confounders [41.7±27.8% (N = 1440 cycles) versus 37.5±25.7% in a disturbed incubator (N = 2265 cycles); unstandardized B-coefficient:+5.6%, 95%CI +3.9% to + 7.3%, standardized beta-coefficient:-0.103,p<0.01].

The main confounders on LBR per SET (overall: N = 1044/2604, 40.1%) were oocyte age, number of consecutive transfer, blastocyst chromosomal status (untested/euploid), quality and day. The univariate logistic regressions showed a benefit for undisturbed incubators (OR:1.3, 95%CI 1.1-1.5, p < 0.01), humidified atmosphere (OR:1.4, 95%CI 1.1-1.7, p < 0.01) and media refresh (OR:1.3, 95% 1.01-1.8, p = 0.05). However, only the use of drops ≥80ml with a well-of-the-well approach rather than drops ≤30ml with a single-culture approach involved an improvement when adjusting for confounders (untested SETs: N = 71/171, 41.5% versus N = 434/1284, 33.8%; euploid SETs: N = 170/316, 53.8% versus N = 369/833, 44.3%; multivariate-OR:1.33, 95%CI 1.12-1.58, adjusted p-value<0.01). This result was confirmed in a sub-analysis across only first patients’ SETs.

Lastly, no feature under investigation was associated with embryo-twinning (overall: N = 23/1243, 1.9% and N = 14/1044, 1.3% per pregnancy and delivery, respectively).

Limitations, reasons for caution

Retrospective single center study. Only ICSI cycles and continuous culture media were assessed. Cleavage stage SETs were excluded. All operators had at least 3yr of experience. Perinatal and gestational outcomes were not evaluated.

Wider implications of the findings

Real-life data adjusted for confounders may unveil fluctuations in critical KPIs mainly imputable to culture strategies. An impact seldom derives from oocyte/embryo manipulations if experienced operators adopt validated protocols. An accurate interpretation of these evidence shall lead to properly designed studies with problem-solving/progress-building purposes, and guidelines to standardize culture practices.

Trial registration number

Not applicable

O-101 Elucidation of blastocyst collapse and its consequences: a comprehensive artificial intelligence-powered analysis of 1943 embryos from 643 couples

Study question

What are the causes and consequences of blastocyst collapse?

Summary answer

∼50% of blastocysts collapsed, especially if they are aneuploid and/or morphologically-poor. Yet, no impact on the live-birth-rate (LBR) per vitrified-warmed euploid single-embryo-transfer (SET) was reported.

What is known already

Time-lapse-microscopy (TLM) is a powerful tool to describe the peculiar dynamics of preimplantation development. Lately, artificial intelligence (AI) has been also implemented to automatize and standardize such description. Here, we adopted AI to comprehensively portray blastocyst collapse, namely the phenomenon of embryo contraction with an efflux of blastocoel fluid and the detachment of the trophectoderm (TE) from the Zona Pellucida (ZP). Although, the causes of this event are still undetermined, small blastocyst contractions have been reported beneficial for the hatching process, while a full collapse has been associated with lower competence.

Study design, size, duration

Observational study including 1943 blastocysts from 643 couples cultured in the Embryoscope between January-2013 and December-2020. TE biopsy without day3 ZP drilling and comprehensive-chromosome-testing were performed. The Fairtility® software automatically registered: (i)time of starting-blastulation (tSB), (ii)starting and ending time of each collapse (tSC and tEC), (iii)blastocysts’ areas, (iv)shrinkage% [(area at SC – area at EC)/area at SC)], (v)embryo:ZP ratio at EC (area of the collapsed embryo/area of the ZP), and (vi)time of biopsy (t-biopsy).

Participants/materials, setting, methods

Blastocyst quality was defined according to Istanbul Consensus (11, excellent; 12-21, good; 22-13-31, average; 33-23-32, poor) and with the Fairtility implantation score (IS) as well, i.e., a continuous variable from 0 to 1 generated by the KID+ software based on the TLM videos of preimplantation development. The main outcome was the LBR per euploid SET adjusted for confounders through logistic regressions. All couple and embryo features were also investigated for their association with blastocyst collapse.

Main results and the role of chance

47.3% of the blastocysts collapsed 1- to 9-times (interval between collapses: 4-8hr), and 73% of the couples had ≥1 collapsed blastocyst (1.8±1.1, range:1-8). No couple feature, though, was associated with blastocyst collapse. The longest collapses lasted 1.5±1.1 (0.13-5.1)hr, while the largest shrinkage% and embryo:ZP ratio at EC were 35±14% (10-78%) and 81±9% (33-90%), respectively. In ∼50-60% of collapses a 20-40% blastocyst volume reduction was registered, 40-60% or 20-40% in ∼15-30%, 60-80% in 0-4%. In case of multiple collapses, the first three involved smaller shrinkages. Blastocysts undergoing ≥1 collapse showed similar tSB as not-collapsing blastocysts, but progressively longer tEB and t-biopsy. The earlier the first event, the more the consecutive collapses. Notably, the poorer the morphology, the higher the risk (excellent, good, average, and poor not-collapsing blastocysts were 64%,50%,44% and 37%), number (e.g.,≥4 collapses were 0.4%,2%,4% and 8%) and duration (1.2±1.0,1.4±1.0,1.6±1.1 and 1.9±1.3hr) of blastocyst collapse. Collapsing blastocysts were significantly less euploid than non-collapsing (35% vs 47%; multivariate-OR:0.75,95%CI 0.6-0.92,p<0.01); conversely, their LBR per euploid SET (39% vs 46%) and miscarriage rate per clinical pregnancy (17% vs 11%), were not significantly different (adjusted-OR:1.0,95%CI 0.69-1.48,p=0.96 and adjusted-OR:1.65,95%CI 0.79-3.42,p=0.18, respectively). All data were confirmed also by defining blastocyst quality through the Fairtility IS.

Limitations, reasons for caution

Gestational and perinatal outcomes were not assessed. Other culture strategies and media shall be assessed for their association with blastocyst collapse. Perhaps, future studies from other groups and with a larger sample size might unveil a significant impact on the clinical outcomes.

Wider implications of the findings

Collapse is common and delays blastocyst full-expansion. Moreover, poor morphology and aneuploidies involve a higher risk of collapse(s); however, no impact was reported on the clinical outcomes after euploid SET. AI appears to increase the throughput of the analysis, but additional data are required to research the causes of collapse.

Trial registration number

Not applicable

O-121 Uncovering the value of day 7 blastocysts using artificial intelligence on time lapse videos

Study question

Which is the clinical value of day 7 blastocysts?

Summary answer

Ending embryo culture at 144 hours-post-insemination (hpi) would involve7.3%- and 4.4%-relative reductions in the 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 at ironing 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, 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

Trophectoderm biopsy without hatching and comprehensive-chromosome-testing were performed. Blastocysts were clustered in six groups based on the time-of-biopsy every 12hr from <120hpi (control) to > 168hpi. Blastocyst quality, time-of-expanding-blastocyst (tEB) and duration of expansion were annotated through AI and confirmed manually. The main outcomes were euploidy-rate and LB-rate (LBR) per transfer. Lastly, patients obtaining (euploid) blastocysts, LBs, and supernumerary blastocysts, were reported based on a hypothetical 144hpi cut-off, and all relative reductions calculated.

Main results and the role of chance

14.6% of the blastocysts reached full expansionbeyond 144hpi (5.9% between 144-156hpi, 7.9% between 156-168hpi, and 0.8% >168hpi). Slower blastocysts were of a worse quality based on the evaluation of both embryologists and AI. Both longer tEB and a longer duration of expansion concurred to day7 development, quite independently of embryo quality. The lower euploidy rate among day7 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 132-144hpi (N = 76/208, 36.5% versus N = 114/215, 53.0% in the control, multivariate-OR: 0.61, 95%CI 0.40-0.92, adjusted-p=0.02), and a second step for blastocysts biopsied in the range 156-168hpi (N = 3/21, 14.3%, multivariate-OR:0.24, 95%CI 0.07-0.88, adjusted-p=0.03). Nevertheless, when the cut-off was set at 144hpi, no significant difference was reported. In this patient population, ending embryo culture at 144hpi would have caused 10.6%-, 7.3%-, 4.4%-, 13.7%-, and 5.2%-relative reductions in the number ofpatients obtaining blastocysts, euploid blastocysts, LBs, supernumerary blastocysts without a LB and after a LB, respectively.

Limitations, reasons for caution

Gestational and perinatal outcomes were not assessed, and a cost-effectiveness analysis was not performed. We encourage the production of these data in other clinical settings and regulatory contexts.

Wider implications of the findings

Day7 culture shall be supported following a careful case-by-case evaluation. Patients shall be aware of their lower competence, yet day7 blastocysts are valuable for poor-prognosis couples, couples less compliant towards other attempts in case of failures, and couples wishing for second children. AI may improve the generalizability of these evidence.

Trial registration number

Not applicable

P–783 Clinical, obstetric and perinatal outcomes after vitrified-warmed euploid blastocyst transfer are independent of cryo-storage duration

Study question

Is cryo-storage duration associated with the outcomes after vitrified-warmed euploid single blastocyst transfer?

Summary answer

Lower live-birth-rates from blastocysts cryo-stored for periods longer than 3-months are mostly imputable to the worse quality of the embryos being warmed across sequential transfers.

What is known already

Blastocyst vitrification is crucial in modern IVF. Given its widespread application, a constant comprehensive monitoring of its effect on reproductive outcomes is pivotal. For instance, the effect of cryo-storage duration on embryo implantation potential, gestational and perinatal outcomes is object of a still ongoing investigation. The evidence in this regard are contrasting especially with regard to similar or decreased live birth rates among blastocysts subject to long-term cryo-storage. When investigating the neonatal outcomes, instead, no impact of blastocyst cryo-storage duration has ever been reported to date. Yet, data on euploid blastocysts and adjusted for quality and full-blastulation day are needed.

Study design, size, duration

Retrospective observational study. We included 2688 vitrified-warmed euploid single blastocyst transfers. The primary outcome was the live-birth-rates (LBR) according to cryo-storage duration clustered as ≤ 60, 61–90, 91–180, 181–360, 361–720, 721–1080 and >1080-days. The secondary outcomes were the miscarriage rate, the rates of gestational and perinatal issues among the deliveries, and the mean gestational age and birthweight among the babies born. All data were adjusted for confounders through linear or logistic regression analyses. Participants/materials, setting, methods: We included all vitrified-warmed transfers (range:1–8) conducted between May–2013 and March–2020 by 1884 patients (age:38±3yr) undergoing one blastocyst stage PGT-A cycle and obtaining ≥1 euploid embryo at our private clinic. Among putative confounders, only the number of sequential transfer from the same patient, blastocyst quality (Gardner’s scheme) and full-blastulation day (5–7) significantly associated with the LBR through univariate regressions. No association was reported for sperm factor, maternal age, incubator, and culture media.

Main results and the role of chance

The LBR of euploid blastocysts cryo-stored for ≤60-days was 49.4% (N = 319/646) versus 48.7% (N = 292/599; OR:0.98,95%CI:0.78–1.21,p=0.82) between 61–90-days, 42.9% (N = 291/679; OR:0.77,95%CI:0.62–0.96,p=0.02) between 91–180-days, 41.7% (N = 169/405; OR:0.73,95%CI:0.57–0.94,p=0.02) between 181–360-days, 34.7% (N = 50/144; OR:0.55,95%CI:0.37–0.79,p<0.01) between 361–720-days, 53.4% (N = 63/118; OR:1.17,95%CI:0.79–1.74,p=0.42) between 721–1080-days, and 50.5% (N = 49/97; OR:1.05,95%CI:0.68–1.60,p=0.83) for >1080-days. However, when these data were adjusted for blastocyst quality and full-blastulation day, all the multivariate-OR were not-significant. Indeed, the longer the cryo-storage period the worse the quality of the euploid blastocysts transferred (e.g. AA-blastocysts were 74% among embryos cryo-stored for ≤90-days, but always <70% for embryos cryo-stored for longer periods, p < 0.01; similarly, day5-blastocysts were ∼50% among embryos cryo-stored for ≤90-days, but always <50% for embryos cryo-stored for longer periods, p = 0.02). The miscarriage-rate (overall 14%, ranging 7–18%) was not associated with cryo-storage duration already from univariate regressions. Also the gestational (overall 6%, ranging 0–8%) and perinatal issues rates (overall 3%, ranging 0–5%) were not associated with cryo-storage duration already from the univariate regressions. Neither the gestational age nor the birthweight showed significant associations with cryo-storage duration, as confirmed by linear regressions. In fact the rate of newborns whose weight was normal-for-gestational-age was similar across all cryo-storage duration groups (overall 81%, ranging 80–83%).

Limitations, reasons for caution

The prevalence of first transfers decreases from ≥95% for procedures conducted ≤90-days from vitrification to 71%, 39%, 22% and 4% for procedures conducted between 91–180, 181–360, 361–720 and >720-days, respectively. However, also the sequential number of transfer was not associated with the LBR when adjusted for blastocyst-quality and full-blastulation day.

Wider implications of the findings: Cryo-storage by vitrification is confirmed safe in the hands of experienced operators, and its duration does not impact any outcome. This information is valuable for freeze-all cycles, but also for women cryo-preserving surplus embryos for second pregnancies; in this regard, 6.8% of the patients in this study delivered ≥2 LBs.

Trial registration number

Not applicable

P–752 Embryo morphological grading across several IVF centers is not consistent but an interactive training is useful to improve its consistency

Study question

Are the embryologists across several IVF clinics concordant when evaluating embryo morphology?

Summary answer

Embryo morphological grading is sufficiently consistent among embryologists from the same center, while an interactive training was essential to improve its accuracy across several clinics.

What is known already

Embryo morphology, mostly at the blastocyst stage, is the strongest non-invasive embryological feature that associates with implantation potential. This association is confirmed also when euploid blastocysts are transferred. At present, several embryo grading schemes exist but is still unclear which is the most effective among them. Moreover, many IVF clinics adopt internal embryo grading scores, further limiting the transferability of this crucial prognostic information across different laboratories. With the aim of assessing the level of concordance in embryo grading within and between IVF clinics, the Italian Society of Embryology, Reproduction and Research (SIERR) conceived this study.

Study design, size, duration

We photographed 40 cleavage-stage and 40 blastocyst-stage embryos (3 focal-planes=240 photos). Two embryologists (senior and junior) from 65 Italian IVF clinics were invited to grade them. Their evaluations were blindly collected as Phase-I (January2020-March2020). Phase-II consisted of an interactive-training on Google-Classroom during which 6 selected experts found a Consensus on the morphological evaluation of the 80 embryos (April2020). As Phase III (May2020-July2020), a second set of 240 pictures was sent to senior participants and experts.

Participants/materials, setting, methods

Eighteen centers agreed to participate, and 36 embryologists were included. The embryo grading scheme adopted was the Alpha-ESHRE Istanbul Consensus (parameters: cleavage-stage blastomeres’ symmetry and fragmentation, blastocyst’s expansion, inner-cell-mass and trophectoderm quality), conventionally used in 50% of the centers (N = 9/18). The concordance within (junior versus senior) and between (senior versus experts) centers was calculated through the Cohen’s-k. The concordance between centers was compared before and after the interactive training on the two sets of pictures.

Main results and the role of chance

The centers and embryologists included were representative of the Italian IVF scenario: oocyte-retrievals per year:711±636,range100–2200; cycles with cleavage-stage embryo-transfer:322±339,0–1300; cycles with blastocyst-stage embryo-transfer:390±403,0–1100; operators per center:5.6±4.0,2–13; senior embryologists’ experience:14.8±7.4yr,7–30; junior embryologists’ experience:2.7±0.6yr,1–3. The intra-center concordance was (i)for blastomeres’ symmetry 82±15% (38–100%), k 0.59±0.27 (0.02–1), (ii)for blastomeres’ fragmentation 88±9% (65–100%), k 0.71±0.2 (0.29–1), (iii)for blastocysts’ expansion 80±16% (48–100%), k 0.66±0.27 (0.19–1), (iv)for inner-cell-mass quality 73±16% (35–95%), k 0.58±0.24 (0.07–0.92), (v)for trophectoderm quality 71±19% (38–95%), k 0.54±0.32 (0.01–0.97). Linear regressions showed no association of centers’ and embryologists’ characteristics with all k-values.

Among clinics with the highest mean number of cycles per year and intra-center concordance, we selected 6 experts for the interactive-training. We then calculated the inter-center concordance as the agreement rate between senior embryologists and the experts for phase-I and phase-III: (i)for blastomeres’ symmetry 67±15% (30–85%) and 73±17% (15–90%;Wilcoxon-signed-ranks-test=0.06), k 0.33±0.22 (–0.29–0.58) and 0.42±0.33 (–0.56–0.77); (ii)for blastomeres’ fragmentation 81±17% (23–95%) and 83±14% (50–95%;Wilcoxon-signed-ranks-test=0.8), k 0.54±0.22 (–0.05–0.84) and 0.55±0.22 (0.17–0.81); (iii)for blastocysts’ expansion 59±16% (35–85%) and 67±17% (23–90%;Wilcoxon-signed-ranks-test=0.04), k 0.35±0.20 (0.06–0.73) and 0.44±0.22 (–0.10–0.7); (iv)for inner-cell-mass quality 60±14% (33–80%) and 69±11% (48–85%;Wilcoxon-signed-ranks-test=0.02), k 0.40±0.20 (0.01–0.69) and 0.51±0.18 (0.18–0.77); (v)for trophectoderm quality 55±12% (23–70%) and 63±10% 48–78%;Wilcoxon-signed-ranks-test<0.01), k 0.29±0.15 (–0.08–0.52) and 0.42±0.15 (0.21–0.66).

Limitations, reasons for caution

Only 28% (N = 18/65) of the Italian IVF centers invited to participate responded to the survey. The conventional adoption of grading schemes other than Istanbul-Consensus by 50% of the embryologists might have biased their evaluation. The experts were not fully-concordant in grading 13.8% of the embryos (N = 22/160), which required active discussions.

Wider implications of the findings: Blastocyst-grading concordance was significantly improved after the training phase. Therefore, interactive consensus meetings and training platforms are keenly needed to standardize this practice across the centers. The “avant-garde” of artificial intelligence applied to embryo image analysis might help overcoming this issue in the future.

Trial registration number

N.A.

P–210 Abnormal cleavage patterns during embryo preimplantation development and their effect on blastulation: an overview from IVF patients with multiple IVF cycles in a time-lapse incubator

Study question

How common abnormal cleavage patterns (ACP) are in IVF and what are their consequences on embryo developmental competence?

Summary answer

ACP might affect up to 25% of the 2PN-zygotes, independently from patients’/cycles’ characteristics, and mostly cause embryo developmental arrest around the 4-to–8-cell transition.

What is known already

Since its implementation in IVF, time-lapse-microscopy (TLM) allowed the standardization of embryo culture within undisturbed incubators, but it has not improved embryo selection especially if blastocyst transfer is performed. Nevertheless, TLM holds the potential for boosting our knowledge of embryo preimplantation development. In particular, a continuous observation of embryo morpho-dynamics unveiled peculiar blastomere cleavage patterns previously unidentifiable with a static morphological assessment. These events are possibly associated with massive mitotic errors, affecting both chromosomes and cytoskeletal components, as well as downstream metabolic imbalances. Still, the causes of ACP and their consequences on embryo developmental/reproductive competence require further investigation.

Study design, size, duration

Observational study including 75 patients (age:38.6±3.7yr, FSH:8.8±3.6IU/l, AMH:1.7±1.3ng/ml; BMI:21.4±2.4) who conducted multiple IVF cycles (N = 160; 8.7±5.0 cumulus-oocyte-complexes and 6.3±3.6 metaphase-II collected; 201±245 days between first and second cycles) in a time-lapse incubator between 2014–2020. All annotations were performed blindly by two operators and confirmed by a third in case of discordance. The outcomes were the blastulation rate after any ACP, their association between each other and with patients’/cycles’ characteristics.

Participants/materials, setting, methods

We included only ICSI-cycles after ovarian-stimulation with blastocyst culture conducted in the Embryoscope. Overall, 981 metaphase-II were inseminated and 677 2PN-zygotes annotated. The ACP investigated were: (i)cytokinesis-failure, formation of cytoplasmic septa without cell division; (ii)Chaotic-cleavage, disordered and uneven cleavages; (iii)Direct-unequal-cleavage (DUC), cleavage of zygotes or single blastomeres directly into 3; (iv)Rapid-cleavage, t3-t2<5hr; (v)Reverse-cleavage, fusion of 2 blastomeres into 1; (vi)Fragmentation, presence of numerous non-nucleated fragments; (vii)Blastomeres’ exclusion/extrusion, nucleated cells excluded/extruded from the morula.

Main results and the role of chance

Among the 2PN-zygotes, the prevalence of cytokinesis-failure was 5.9% (N = 40/677), 15.7% for chaotic-cleavage (N = 106/677), 18.6% for DUC (N = 126/677), 4.1% for rapid-cleavage (N = 28/677), 3.5% for reverse-cleavage (N = 24/677) and 24.1% for fragmentation (N = 163/677). Among the morulae, the prevalence of blastomere exclusion/extrusion was 27% (N = 109/410;1.5±1.2 excluded/extruded cells,range:1–7). The risk for reverse-cleavage was higher among 2PN-zygotes facing failed-cytokinesis (N = 8/40,20% versus N = 16/637,2.5%, OR:9.7,95%CI:3.9–24.3,p<0.01). Fragmentation was instead higher among 2PN-zygotes undergoing chaotic cleavage (N = 47/106,44.3% versus N = 116/571,20.3%, OR:3.1,95%CI:2–4.8,p<0.01) or DUC (N = 46/126,36.5% versus N = 117/551,21.2%, OR:2.1,95%CI:1.4–3.2,p<0.01). Lastly, higher prevalence of blastomeres’ exclusion/extrusion were reported among morulae obtained after chaotic-cleavage (N = 17/29,58.6% versus N = 92/381,24.1%, OR:4.4,95%CI:2–9.7,p<0.01), DUC (N = 26/37,70.3% versus N = 83/373,22.3%, OR:8.3,95%CI:3.9–17.4,p<0.01) and in presence of fragmentation (N = 79/195,75.2% versus N = 30/305,9.8%, OR:27.8,95%CI:15.6–49.8,p<0.01); only a higher trend after rapid-/reverse-cleavage.

No predictive factor of ACP was identified among patients’ and cycles’ characteristics, except for higher risks of fragmentation (OR:2.6,95%CI:1.1–6.3,p= 0.04) and blastomeres’ exclusion/extrusion (OR:2.7,95%CI:1.1–7.2,p=0.04) among patients with previous experience with these events.

The viable-blastocyst rate per 2PN-zygote was 45.1% (N = 305/677). It was lower in case of failed-cytokinesis (N = 12/40,30% versus N = 293/637,46%, OR:0.5,95%CI:0.25–0.99,p=0.05), chaotic cleavage (N = 20/106,18.9% versus N = 285/571,49.9%, OR:0.23,95%CI:0.14–0.39,p<0.01), DUC (N = 27/126,21.4% versus N = 278/551,50.5%, OR:0.27,95%CI:0.17–0.42,p<0.01), rapid-cleavage (N = 6/22,21.4% versus N = 299/649,46.1%, OR:0.32,95%CI:0.13–0.8,p=0.02), and reverse-cleavage (N = 5/19,20.8% versus N = 300/653,45.9%, OR:0.31, 95%CI:0.11–0.84,p=0.02). No difference was instead shown in case of fragmentation and/or blastomeres’ exclusion/extrusion.

Limitations, reasons for caution

The patients included were poor-prognosis women undergoing ≥2 cycles. We are expanding the sample size to account for all cycles conducted in time-lapse incubators. Larger sample size will provide also statistical-power to investigate the effect of ACP on blastocysts’ chromosomal and implantation competence, and more visualizations of rapid-/reverse-cleavage events.

Wider implications of the findings: After ACP,developmental-arrest mostly occurs around the 4-to–8-cell transition (50–70% versus ∼30%), when embryonic-genome-activation takes place. Surviving embryos often fragment and/or exclude/extrude blastomeres at morulation, without further impact on blastulation-rates. Moreover, ACP seem independent from patients’/cycles’ characteristics. These evidence incite future Research on the biological/genetic mechanisms triggering ACP and their consequences.

Trial registration number

None

P-783 Clinical, obstetric and perinatal outcomes after vitrified-warmed euploid blastocyst transfer are independent of cryo-storage duration

Study question

Is cryo-storage duration associated with the outcomes after vitrified-warmed euploid single blastocyst transfer?

Summary answer

Lower live-birth-rates from blastocysts cryo-stored for periods longer than 3-months are mostly imputable to the worse quality of the embryos being warmed across sequential transfers.

What is known already

Blastocyst vitrification is crucial in modern IVF. Given its widespread application, a constant comprehensive monitoring of its effect on reproductive outcomes is pivotal. For instance, the effect of cryo-storage duration on embryo implantation potential, gestational and perinatal outcomes is object of a still ongoing investigation. The evidence in this regard are contrasting especially with regard to similar or decreased live birth rates among blastocysts subject to long-term cryo-storage. When investigating the neonatal outcomes, instead, no impact of blastocyst cryo-storage duration has ever been reported to date. Yet, data on euploid blastocysts and adjusted for quality and full-blastulation day are needed.

Study design, size, duration

Retrospective observational study. We included 2688 vitrified-warmed euploid single blastocyst transfers. The primary outcome was the live-birth-rates (LBR) according to cryo-storage duration clustered as ≤ 60, 61-90, 91-180, 181-360, 361-720, 721-1080 and >1080-days. The secondary outcomes were the miscarriage rate, the rates of gestational and perinatal issues among the deliveries, and the mean gestational age and birthweight among the babies born. All data were adjusted for confounders through linear or logistic regression analyses.

Participants/materials, setting, methods

We included all vitrified-warmed transfers (range:1-8) conducted between May-2013 and March-2020 by 1884 patients (age:38±3yr) undergoing one blastocyst stage PGT-A cycle and obtaining ≥1 euploid embryo at our private clinic. Among putative confounders, only the number of sequential transfer from the same patient, blastocyst quality (Gardner’s scheme) and full-blastulation day (5-7) significantly associated with the LBR through univariate regressions. No association was reported for sperm factor, maternal age, incubator, and culture media.

Main results and the role of chance

The LBR of euploid blastocysts cryo-stored for ≤60-days was 49.4% (N = 319/646) versus 48.7% (N = 292/599; OR:0.98,95%CI:0.78-1.21,p = 0.82) between 61-90-days, 42.9% (N = 291/679; OR:0.77,95%CI:0.62-0.96,p = 0.02) between 91-180-days, 41.7% (N = 169/405; OR:0.73,95%CI:0.57-0.94,p = 0.02) between 181-360-days, 34.7% (N = 50/144; OR:0.55,95%CI:0.37-0.79,p < 0.01) between 361-720-days, 53.4% (N = 63/118; OR:1.17,95%CI:0.79-1.74,p = 0.42) between 721-1080-days, and 50.5% (N = 49/97; OR:1.05,95%CI:0.68-1.60,p = 0.83) for >1080-days. However, when these data were adjusted for blastocyst quality and full-blastulation day, all the multivariate-OR were not-significant. Indeed, the longer the cryo-storage period the worse the quality of the euploid blastocysts transferred (e.g. AA-blastocysts were 74% among embryos cryo-stored for ≤90-days, but always < 70% for embryos cryo-stored for longer periods, p < 0.01; similarly, day5-blastocysts were ∼50% among embryos cryo-stored for ≤90-days, but always < 50% for embryos cryo-stored for longer periods, p = 0.02). The miscarriage-rate (overall 14%, ranging 7-18%) was not associated with cryo-storage duration already from univariate regressions. Also the gestational (overall 6%, ranging 0-8%) and perinatal issues rates (overall 3%, ranging 0-5%) were not associated with cryo-storage duration already from the univariate regressions. Neither the gestational age nor the birthweight showed significant associations with cryo-storage duration, as confirmed by linear regressions. In fact the rate of newborns whose weight was normal-for-gestational-age was similar across all cryo-storage duration groups (overall 81%, ranging 80-83%).

Limitations, reasons for caution

The prevalence of first transfers decreases from ≥95% for procedures conducted ≤90-days from vitrification to 71%, 39%, 22% and 4% for procedures conducted between 91-180, 181-360, 361-720 and >720-days, respectively. However, also the sequential number of transfer was not associated with the LBR when adjusted for blastocyst-quality and full-blastulation day.

Wider implications of the findings

Cryo-storage by vitrification is confirmed safe in the hands of experienced operators, and its duration does not impact any outcome. This information is valuable for freeze-all cycles, but also for women cryo-preserving surplus embryos for second pregnancies; in this regard, 6.8% of the patients in this study delivered ≥2 LBs.

Trial registration number

not applicable

P–519 Investigation of embryo chromosomal constitution and live birth rate after vitrified-warmed euploid single blastocyst transfer across ranges of maternal body-mass-index

Study question

Does maternal body-mass-index (BMI) associate with blastocysts’ chromosomal constitution and clinical outcomes in infertile patients undergoing preimplantation genetic testing for aneuploidies (PGT-A)?

Summary answer

A higher euploidy rate per biopsied blastocyst was reported among underweight women. Overweight women were instead subject to higher miscarriage (MR) and lower live-birth-rates (LBR).

What is known already

Different studies in the literature revealed an association between BMI and infertility, suggesting a J-shaped relationship: both underweight and overweight women can suffer from infertility issues. Even if IVF might increase the success rate in both these categories of patients, it seems insufficient per se to overcome the complex and multifactorial fertility impairment derived from unbalanced nutritional intakes. Miscarriage, in particular, is common in both underweight and overweight women. However, most of the literature is based on chromosomally-untested embryos. Study design, size, duration: Retrospective observational study. Only the first IVF cycle with ≥1 biopsied blastocyst from each woman was included. The primary outcome was the association between maternal BMI (underweight, BMI<18.5, n = 160; normal-weight, BMI=18–25, N = 1392; overweight, BMI>25, N = 259) and the mean euploidy rate per cohort of biopsied blastocysts (m-ER). The secondary outcomes were the association between maternal BMI with clinical (mainly MR and LBR), gestational and perinatal outcomes after first vitrified-warmed single euploid blastocyst transfers.

Participants/materials, setting, methods

We included 1811 women undergoing PGT-A at a private IVF center between April–2013 and March–2020. The secondary outcomes were investigated on 1125 first vitrified-warmed single euploid blastocyst transfers from all patients obtaining ≥1 transferable blastocyst. Only ICSI with ejaculated sperm and continuous culture in standard incubators were performed. Logistic regressions were conducted to identify putative confounders and adjust the results accordingly.

Main results and the role of chance

Except for a lower maternal age among underweight women (38.3±3.1 versus 38.9±3.4 yr, p < 0.01) and higher among overweight ones (39.3±3.6 yr, p = 0.04), no difference was reported with respect to normal-weight women in terms of duration of infertility, hormonal levels, main cause of infertility, sperm quality, and reproductive history. The mean number of biopsied blastocysts was ∼3 in all groups. The m-ER shows a decreasing trend as the maternal BMI increases between 17 and 22–23, to then plateau. In fact, a significant difference was reported between underweight (50.8%±36.4%) and normal-weight women (41.4%±37.5%, p < 0.01). A linear regression adjusted for maternal age confirmed this moderate association between increasing BMI and m-ER (unstandardized-coefficient-B –0.6%, 95%CI:–1.1% to –0.1%, p = 0.02).

Morphological quality and day of full-blastulation among transferred euploid blastocysts was similar in the three groups. Overweight women showed higher MR per pregnancy (N = 20/75, 26.7%, 95%CI:17.4%–38.3% versus N = 67/461, 14.5%, 95%CI:11.5%–18.2%; OR 2.0, 95%CI:1.1–3.6, p = 0.01) and lower LBR per transfer (N = 55/154, 35.7%, 95%CI:28.3%–43.8% versus N = 388/859, 45.2%, 95%CI:41.8%–48.6%; OR adjusted for euploid blastocysts’ features 0.67, 95%CI:0.46–0.96, p = 0.03). Clinical outcomes were instead similar among underweight and normal-weight women. All gestational and perinatal outcomes were comparable in the tree groups.

Limitations, reasons for caution

Our study is limited by its retrospective nature, and the fact that maternal BMI was measured only before oocyte retrieval and not before embryo transfer. Moreover, the reduced sample size did not allow for further relevant sub-analyses among solely obese women.

Wider implications of the findings: When possible nutritional/lifestyle modifications should be encouraged to adjust maternal BMI before IVF. Overweight patients should be especially informed of their higher risk for miscarriage. Yet, BMI is just a gross marker, future studies based on body fat localization and percentage (e.g. by bioelectrical impedance analyses) are desirable.

Trial registration number

None

Controlled placement of multiple CNS cell populations to create complex neuronal cultures

In vitro brain-on-a-chip platforms hold promise in many areas including: drug discovery, evaluating effects of toxicants and pathogens, and disease modelling. A more accurate recapitulation of the intricate organization of the brain in vivo may require a complex in vitro system including organization of multiple neuronal cell types in an anatomically-relevant manner. Most approaches for compartmentalizing or segregating multiple cell types on microfabricated substrates use either permanent physical surface features or chemical surface functionalization. This study describes a removable insert that successfully deposits neurons from different brain areas onto discrete regions of a microelectrode array (MEA) surface, achieving a separation distance of 100 μm. The regional seeding area on the substrate is significantly smaller than current platforms using comparable placement methods. The non-permanent barrier between cell populations allows the cells to remain localized and attach to the substrate while the insert is in place and interact with neighboring regions after removal. The insert was used to simultaneously seed primary rodent hippocampal and cortical neurons onto MEAs. These cells retained their morphology, viability, and function after seeding through the cell insert through 28 days in vitro (DIV). Co-cultures of the two neuron types developed processes and formed integrated networks between the different MEA regions. Electrophysiological data demonstrated characteristic bursting features and waveform shapes that were consistent for each neuron type in both mono- and co-culture. Additionally, hippocampal cells co-cultured with cortical neurons showed an increase in within-burst firing rate (p = 0.013) and percent spikes in bursts (p = 0.002), changes that imply communication exists between the two cell types in co-culture. The cell seeding insert described in this work is a simple but effective method of separating distinct neuronal populations on microfabricated devices, and offers a unique approach to developing the types of complex in vitro cellular environments required for anatomically-relevant brain-on-a-chip devices.

Long-term non-invasive interrogation of human dorsal root ganglion neuronal cultures on an integrated microfluidic multielectrode array platform

Scientific studies in drug development and toxicology rely heavily on animal models, which often inaccurately predict the true response for human exposure. This may lead to unanticipated adverse effects or misidentified risks that result in, for example, drug candidate elimination. The utilization of human cells and tissues for in vitro physiological platforms has become a growing area of interest to bridge this gap and to more accurately predict human responses to drugs and toxins. The effects of new drugs and toxins on the peripheral nervous system are often investigated with neurons isolated from dorsal root ganglia (DRG), typically with one-time measurement techniques such as patch clamping. Here, we report the use of our multi-electrode array (MEA) platform for long-term noninvasive assessment of human DRG cell health and function. In this study, we acquired simultaneous optical and electrophysiological measurements from primary human DRG neurons upon chemical stimulation repeatedly through day in vitro (DIV) 23. Distinct chemical signatures were noted for the cellular responses evoked by each chemical stimulus. Additionally, the cell viability and function of the human DRG neurons were consistent through DIV 23. To the best of our knowledge, this is the first report on long-term measurements of the cell health and function of human DRG neurons on a MEA platform. Future generations will include higher electrode numbers in customized arrangements as well as integration with different tissue types on a single device. This platform will provide a valuable testing tool for both rodent and human cells, enabling a more comprehensive risk assessment for drug candidates and toxicants.