Should extended blastocyst culture include Day 7?

Is a day 7 blastocyst predictive of the reproductive potential of sibling day 5 and day 6 blastocysts?

PURPOSE

To explore if a day 7 blastocyst is predictive of the reproductive potential of sibling day 5 or day 6 blastocysts?

METHODS

Retrospective cohort of autologous frozen embryo transfers (FET), February 2019 to April 2022. Cycles divided into groups 1 to 5, according to the day of embryo cryopreservation and the presence of a day 7 blastocyst sibling within the cohort: group 1/group 2-day 5 blastocyst without/with a day 7 sibling, group 3/group 4-day 6 blastocyst without/with a day 7 sibling, group 5-day 7 blastocyst. Clinical, ongoing pregnancy and miscarriage rates, cycle, and patient characteristics are reported. Multivariable generalized estimating equations (GEE) logistic regression analysis accounts for confounders and assesses the effect of a sibling day 7 blastocyst on ongoing pregnancy rates of day 5 or day 6 blastocyst FETs.

RESULTS

Ongoing pregnancy rates are 38.4%, 59.5%, 30.8%, 32.7%, and 4.4% in groups 1-5, respectively. When correcting for maternal age, number of oocytes retrieved and discarded per cohort, and ploidy, embryos cryopreserved on either day 6 or day 7 have reduced odds of ongoing pregnancy after FET compared to day 5 blastocysts (OR = 0.76, IQR [0.61-0.95], p-value = 0.01). However, the presence of a day 7 sibling does not significantly affect odds of ongoing pregnancy of day 5 or day 6 blastocysts compared to the same-day blastocyst without a day 7 sibling (p-value = 0.20 and 0.46, respectively). This finding is consistent within both the Preimplantation Genetic Testing for Aneuploidy (PGT-A) unscreened and screened (euploid) embryo subgroups.

CONCLUSIONS

Day of embryo cryopreservation significantly affects ongoing pregnancy rates. However, day 7 embryos within a cohort do not affect the reproductive potential of sibling day 5 and day 6 blastocysts, suggesting that slow embryo development is an embryo-specific trait.

Preimplantation genetic testing for aneuploidy: predictive embryonic factors

PURPOSE

In a preimplantation genetic testing for aneuploidy (PGT-A) cycle, does the blastocyst quality before biopsy, or the day of biopsy, or the embryo hatching status have an impact on either euploidy or the rate of embryo survival after freezing?

METHODS

This was a retrospective study including 6130 biopsied blastocysts coming from 1849 PGT-A cycles performed in our center (2016-2022). Embryos were categorized according to the inner cell mass and trophectoderm quality, using Gardner's scoring (excellent: AA; good: AB, BA, BB; poor: AC, CA, BC, CB, CC); the day of biopsy (5 or 6); and their hatching status (fully hatched blastocysts [FHB] or non-fully hatched blastocysts [nFHB]). The independent relationship between each group and both euploidy and survival rate was assessed.

RESULTS

Excellent-quality embryos were more euploid than both good- and poor-quality embryos (52.69%, 39.69%, and 26.21%; p < 0.001), and day 5-biopsied embryos were more euploid than day 6-biopsied embryos (39.98% and 34.80%; p < 0.001). Survival rates of excellent-quality (92.26%) and good-quality (92.47%) embryos were higher than survival rates in the poor-quality group (84.61%) (p = 0.011 and p = 0.002). Day 5-biopsied embryos survived better than day 6-biopsied embryos (93.71% vs. 83.69%; p < 0.001) and FHB had poorer survival than nFHB (78.61% vs. 93.52%; p < 0.001).

CONCLUSIONS

Excellent-quality and day 5-biopsied embryos are more prone to be euploid than good and poor or day 6-biopsied embryos, respectively. Poor-quality, day 6-biopsied embryos, and FHB have significantly lower survival after biopsy and vitrification.

Molecular profiling of human blastocysts reveals primitive endoderm defects among embryos of decreased implantation potential

Human embryo implantation is remarkably inefficient, and implantation failure remains among the greatest obstacles in treating infertility. Gene expression data from human embryos have accumulated rapidly in recent years; however, identification of the subset of genes that determine successful implantation remains a challenge. We leverage clinical morphologic grading-known for decades to correlate with implantation potential-and transcriptome analyses of matched embryonic and abembryonic samples to identify factors and pathways enriched and depleted in human blastocysts of good and poor morphology. Unexpectedly, we discovered that the greatest difference was in the state of extraembryonic primitive endoderm (PrE) development, with relative deficiencies in poor morphology blastocysts. Our results suggest that implantation success is most strongly influenced by the embryonic compartment and that deficient PrE development is common among embryos with decreased implantation potential. Our study provides a valuable resource for those investigating the markers and mechanisms of human embryo implantation.

Effect of development speed and quality of blastocyst on singleton birthweight in single frozen-thawed blastocyst transfer cycles

Background

Assisted reproductive technology (ART) has revolutionized infertility treatment, leading to a surge in ART-conceived children. Despite its success, ART-born offspring face higher risks of preterm birth (PTB), low birth weight (LBW), and small for gestational age (SGA). The mechanisms behind these outcomes remain unclear, partly attributed to multiple embryo transfers. Recent advancements advocate single blastocyst transfers for improved outcomes. However, the influence of blastocyst quality and development speed on neonatal outcomes is underexplored.

Objective

This study investigated whether blastocyst development speed and quality affect singleton birthweight when the blastocyst is selected for single frozen-thawed blastocyst transfer (FBT).

Methods

Data from patients who performed an FBT cycle at our center from July 2011 to June 2021 were collected and analyzed. Based on the inclusion and exclusion criteria, 420 single FBT cycles were assessed. The women were divided into four groups, Group A (day 5, good-quality blastocysts), Group B (day 5, non-good-quality blastocysts), Group C (day 6, good-quality blastocysts), and Group D (day 6, non-good-quality blastocysts) according to the developmental speed and quality of the transferred blastocyst.

Results

The birthweight was relatively the highest in Group A, which developed rapidly and transferred good quality blastocysts. However, no significant difference existed among the groups (P>0.05). The prevalence of premature birth (PTB), low birth weight (LBW), very low birth weight (VLBW), or high birth weight (HBW) was similar among the four groups (P > 0.05). No correlation existed between birth weight and blastocyst development speed or quality after adjusting for possible confounders (P > 0.05 respectively). However, the difference in the proportion of males born among the four groups was significant, especially in Group D, which was significantly lower than that in Group A (adjusted odds ratio = 0.461, 95% confidence interval: 0.230-0.921, P < 0.05).

Conclusions

This retrospective cohort study suggests that the combined effect of blastocyst development speed and quality on neonatal birthweight is insignificant. The transfer of slow-growing, non-good-quality blastocysts increases the chance of a female baby being born.

Reproductive outcomes with delayed blastocyst development: the clinical value of day 7 euploid blastocysts in frozen embryo transfer cycles

Embryos of optimal development reach blastocyst stage 116 ± 2 h after insemination. Usable D7 blastocysts represent nearly 5% of embryos in IVF with acceptable pregnancy and live birth rates, however data are still limited. Therefore, this study aimed to analyze the ongoing pregnancy rate (OPR) of D7 blastocysts in single euploid frozen embryo transfer (FET) cycles. An observational study was performed including 1527 FET cycles with blastocysts biopsied on D5 (N = 855), D6 (N = 636) and D7 (N = 36). Blastocysts were classified as good (AA/AB/BA), fair (BB) or poor (AC/BC/CC/CA/CB) (Gardner scoring). FETs were performed in natural cycles (NC) or hormone replacement therapy (HRT) cycles. Patient's age differed significantly between D5, D6 and D7 blastocysts FET cycles (33.2 ± 5.6, 34.4 ± 5.3 and 35.9 ± 5.2, P < 0.001). OPRs were higher when D5 euploid blastocysts were transferred compared with D6 and D7 (56.0% vs. 45.3% and 11.1%, P < 0.001). Poor quality blastocysts were predominant in D7 blastocyst FET cycles (good quality: 35.4%, 27.2%, 5.6%; fair quality: 52.1%, 38.5%, 11.1%; poor quality: 12.5%, 34.3%, 83.3%, P < 0.001 for D5, D6 and D7 blastocysts; respectively). OPR was significantly reduced by D7 blastocyst FETs (OR = 0.23 [0.08;0.62], P = 0.004), patient's BMI (OR = 0.96 [0.94;0.98], P < 0.001), HRT cycles (OR = 0.70 [0.56;0.88], P = 0.002) and poor quality blastocysts (OR = 0.33 [0.24;0.45], P < 0.001). OPR is significantly reduced with D7 compared with D5/D6 euploid blastocysts in FET cycles. The older the patient, the more likely they are to have an FET cycle with blastocysts biopsied on D7, therefore culturing embryos until D7 can be a strategy to increase OPR outcomes in patients ≥38 years.

Similar implantation competence in euploid blastocysts developed on day 5 or day 6 in young women: a retrospective cohort study

The results from different studies are inconsistent regarding whether development potential correlated with embryo development speed after single euploid blastocyst transfer. The age-associated reproductive decline is not only because of the difference in aneuploidy rates but also because of metabolic and epigenetic changes of the embryos. Therefore, we aimed to assess the independent effect of embryo development speed on implantation potential in young women. A total of 326 young women who underwent preimplantation genetic testing for monogenic diseases with aneuploidy screening were analyzed. Day-5 and day-6 euploid blastocysts yielded similar implantation rates (65.20 vs. 61.22%). The odds ratio (OR) remained non-significant after adjusting for confounders (adjusted OR = 0.84, 95% confidence interval 0.52-1.36). There was a trend that day-6 euploid blastocysts had a higher miscarriage rate (13.33 vs. 9.20%). However, the live birth delivery rate of day-5 blastocysts was similar to that of day-6 blastocysts (59.20 vs. 53.06%). In the stratified analysis, live birth delivery rates were similar between day-5 and day-6 similarly graded euploid blastocysts (excellent and good, 62.04 vs. 64.71%; average, 58.73 vs. 53.70%; poor, 43.75 vs. 44.44%). Embryo development speed has no obvious impact on implantation competence in young women's vitrified/warmed euploid embryo transfer cycles.

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;

SUMMARY ANSWER

The prevalence of 'discard' answers was 38.7%; nevertheless, embryologists' agreement was overall just fair (Fleiss-k = 0.26).

WHAT IS KNOWN ALREADY

The utilization of LQBs and adoption of culture beyond 144 h post-insemination is increasing worldwide. Although morphology and morphokinetics are associated with embryo developmental competence, previous studies demonstrated significant interobserver variability among embryologists regarding embryo quality assessment and disposition decisions for borderline quality blastocysts.

STUDY DESIGN, SIZE, DURATION

An anonymous survey was run in a large network of IVF centers. A total of 117 embryologists from 6 European countries and 29 IVF centers filled in the survey. Randomly selected anonymous time-lapse videos of 50 Day 7 and/or LQB whole embryo preimplantation development were assessed by the embryologists. The key information on patients/cycles was provided along with each video. All cycles entailed preimplantation genetic testing for aneuploidies. Each embryologist specified whether he/she would have discarded or used ('transfer-fresh'/'cryopreserve'/'biopsy') any embryo. Inter-rater agreement was measured with Fleiss-k.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Examiners were asked about their years of experience, center location, average number of cycles and average maternal age, number of colleagues, and use of time-lapse incubators at their centers. All participants were blinded to artificial intelligence (AI) scores generated by two commercially available software packages, chromosomal diagnosis (all blastocysts were tested for aneuploidies), and clinical outcomes after vitrified-warmed euploid single blastocyst transfer. These data were known only by one embryologist not involved in the survey.

MAIN RESULTS AND THE ROLE OF CHANCE

Participants were Italian (40%, N = 47), Spanish (24%, N = 28), Portuguese (5%, N = 6), Czech (5%, N = 6), Swedish (23%, N = 27), and Icelandic (3%, N = 3). In total, 2263 (38.7%) 'discard' and 3587 (61.3%) 'use' decisions were recorded. Czech, Portuguese, and Italian embryologists expressed lower 'discard' decision rates (mean ± SD 17 ± 7%, range 8-24%; 23 ± 14% range 4-46%; and 27 ± 18% range 2-72%, respectively), while Spanish gave intermediate (37 ± 16% range 4-66%) and Nordic gave higher (67 ± 11% range 40-90%) rates. The prevalence of 'discard' answers was 38.7% out of 5850 choices (mean per embryologist: 39 ± 23% range 2-90%). Only embryologists' country and IVF group were associated with this rate. Overall agreement among embryologists was fair (Fleiss-k = 0.26). The prevalence of 'discard' responses per embryo was 37 ± 24% (range 2-87%). Only the number of sibling blastocysts influenced this rate (i.e. the larger the cohort, the higher the inclination to 'discard'). No difference was shown for the two scores between euploid and aneuploid borderline quality blastocysts, while the embryologists were, by chance, more prone to 'discard' the latter (28.3 ± 21% range 9-71% versus 41.6 ± 24.8% range 2-87%, respectively).

LIMITATIONS, REASONS FOR CAUTION

The survey included only private IVF clinics located in Europe. Moreover, a key variable is missing, namely patients' access to care. Indeed, all embryologists involved in the survey were part of the same network of private IVF clinics, while the embryo disposition decisions might be different in a public setting.

WIDER IMPLICATIONS OF THE FINDINGS

Decision-making by European embryologists regarding Day 7 embryos or LQBs is inconsistent with putative clinical consequences, especially in patients with low prognosis. Although the embryologists could make decisions independent from their local regulations, their mindset and clinical background influenced their choices. In the future, AI tools should be trained to assess borderline quality embryos and empowered with cost-effectiveness information to support embryologists' decisions with more objective assessments.

STUDY FUNDING/COMPETING INTEREST(S)

No external funding was obtained for this study. The authors have no conflict of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

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Key Words

• Day 7 blastocysts
• artificial intelligence
• decision-making
• embryo competence
• low-quality blastocysts

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MESH Headings

• Female
• Humans
• Aneuploidy
• Artificial Intelligence
• Blastocyst/physiology
• Embryo Transfer/methods
• Maternal Age
• Retrospective Studies
• Male

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Affiliation(s)

Viviana Chiappetta IVIRMA Global Research Alliance, GENERA, Clinica Valle Giulia, Rome, Italy
Federica Innocenti IVIRMA Global Research Alliance, GENERA, Clinica Valle Giulia, Rome, Italy
Giovanni Coticchio IVIRMA Global Research Alliance, 9.baby, Bologna, Italy
Aisling Ahlström IVIRMA Global Research Alliance, LIVIO, Göteborg, Sweden
Laura Albricci IVIRMA Global Research Alliance, GENERA, Clinica Valle Giulia, Rome, Italy
Vicente Badajoz IVIRMA Global Research Alliance, GINEFIV, Madrid, Spain
Maria Hebles IVIRMA Global Research Alliance, GINEMED, Sevilla, Spain
Miguel Gallardo IVIRMA Global Research Alliance, GINEMED, Lisbon, Portugal
Francesca Benini IVIRMA Global Research Alliance, DEMETRA, Florence, Italy
Stefano Canosa IVIRMA Global Research Alliance, LIVET, Turin, Italy
Jiří Kumpošt IVIRMA Global Research Alliance, FERTICARE, Prague, Czech Republic
Katarina Milton IVIRMA Global Research Alliance, CARL VON LINNÈ KLINIKEN, Uppsala, Sweden
Diletta Montanino Oliva Department of Biology and Biotechnology "Lazzaro Spallanzani", University of Pavia, Pavia, Italy
Roberta Maggiulli IVIRMA Global Research Alliance, GENERA, Clinica Valle Giulia, Rome, Italy
Laura Rienzi IVIRMA Global Research Alliance, GENERA, Clinica Valle Giulia, Rome, Italy Department of Biomolecular Sciences, University of Urbino "Carlo Bo", Urbino, Italy
Danilo Cimadomo IVIRMA Global Research Alliance, GENERA, Clinica Valle Giulia, Rome, Italy

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Dual laser-assisted hatching: an effective technique to salvage low-grade cleavage-stage embryos and harvest day 7 blastocysts

To investigate whether repeating laser-assisted hatching (LAH) procedure on day 6 low-grade cleavage-stage embryos (LGCEs) helps blastulation. A total of 579 cycles with LGCEs from 2019 to 2022 was retrospectively reviewed. In 323 cycles, single LAH producing small holes (10 μm) was performed on LGCEs on day 4 (D4-LAH). In 256 cycles with persistent LGCEs despite D4-LAH, a repeat LAH procedure was performed on day 6 (Dual-LAH) with a bigger hole (30 μm). We compared day 7 blastocyst formation rate, usable blastocyst rate, and good grade blastocyst rate from these day 6 LGCEs between the two groups. Compared to the D4-LAH group, the Dual-LAH group had both higher day 7 blastocyst formation rate (9.4% vs. 3.0%, p < 0.001) and higher day 7 usable blastocyst rates (7.4% vs. 2.1%, p < 0.001). For persistent LGCEs despite single LAH, performing a repeat LAH on day 6 increased day 7 blastocyst formation rate.

Opening the black box: why do euploid blastocysts fail to implant? A systematic review and meta-analysis

BACKGROUND

A normal chromosomal constitution defined through PGT-A assessing all chromosomes on trophectoderm (TE) biopsies represents the strongest predictor of embryo implantation. Yet, its positive predictive value is not higher than 50-60%. This gap of knowledge on the causes of euploid blastocysts' reproductive failure is known as 'the black box of implantation'.

OBJECTIVE AND RATIONALE

Several embryonic, maternal, paternal, clinical, and IVF laboratory features were scrutinized for their putative association with reproductive success or implantation failure of euploid blastocysts.

SEARCH METHODS

A systematic bibliographical search was conducted without temporal limits up to August 2021. The keywords were '(blastocyst OR day5 embryo OR day6 embryo OR day7 embryo) AND (euploid OR chromosomally normal OR preimplantation genetic testing) AND (implantation OR implantation failure OR miscarriage OR abortion OR live birth OR biochemical pregnancy OR recurrent implantation failure)'. Overall, 1608 items were identified and screened. We included all prospective or retrospective clinical studies and randomized-controlled-trials (RCTs) that assessed any feature associated with live-birth rates (LBR) and/or miscarriage rates (MR) among non-mosaic euploid blastocyst transfer after TE biopsy and PGT-A. In total, 41 reviews and 372 papers were selected, clustered according to a common focus, and thoroughly reviewed. The PRISMA guideline was followed, the PICO model was adopted, and ROBINS-I and ROB 2.0 scoring were used to assess putative bias. Bias across studies regarding the LBR was also assessed using visual inspection of funnel plots and the trim and fill method. Categorical data were combined with a pooled-OR. The random-effect model was used to conduct the meta-analysis. Between-study heterogeneity was addressed using I2. Whenever not suitable for the meta-analysis, the included studies were simply described for their results. The study protocol was registered at http://www.crd.york.ac.uk/PROSPERO/ (registration number CRD42021275329).

OUTCOMES

We included 372 original papers (335 retrospective studies, 30 prospective studies and 7 RCTs) and 41 reviews. However, most of the studies were retrospective, or characterized by small sample sizes, thus prone to bias, which reduces the quality of the evidence to low or very low. Reduced inner cell mass (7 studies, OR: 0.37, 95% CI: 0.27-0.52, I2 = 53%), or TE quality (9 studies, OR: 0.53, 95% CI: 0.43-0.67, I2 = 70%), overall blastocyst quality worse than Gardner's BB-grade (8 studies, OR: 0.40, 95% CI: 0.24-0.67, I2 = 83%), developmental delay (18 studies, OR: 0.56, 95% CI: 0.49-0.63, I2 = 47%), and (by qualitative analysis) some morphodynamic abnormalities pinpointed through time-lapse microscopy (abnormal cleavage patterns, spontaneous blastocyst collapse, longer time of morula formation I, time of blastulation (tB), and duration of blastulation) were all associated with poorer reproductive outcomes. Slightly lower LBR, even in the context of PGT-A, was reported among women ≥38 years (7 studies, OR: 0.87, 95% CI: 0.75-1.00, I2 = 31%), while obesity was associated with both lower LBR (2 studies, OR: 0.66, 95% CI: 0.55-0.79, I2 = 0%) and higher MR (2 studies, OR: 1.8, 95% CI: 1.08-2.99, I2 = 52%). The experience of previous repeated implantation failures (RIF) was also associated with lower LBR (3 studies, OR: 0.72, 95% CI: 0.55-0.93, I2 = 0%). By qualitative analysis, among hormonal assessments, only abnormal progesterone levels prior to transfer were associated with LBR and MR after PGT-A. Among the clinical protocols used, vitrified-warmed embryo transfer was more effective than fresh transfer (2 studies, OR: 1.56, 95% CI: 1.05-2.33, I2 = 23%) after PGT-A. Lastly, multiple vitrification-warming cycles (2 studies, OR: 0.41, 95% CI: 0.22-0.77, I2 = 50%) or (by qualitative analysis) a high number of cells biopsied may slightly reduce the LBR, while simultaneous zona-pellucida opening and TE biopsy allowed better results than the Day 3 hatching-based protocol (3 studies, OR: 1.41, 95% CI: 1.18-1.69, I2 = 0%).

WIDER IMPLICATIONS

Embryo selection aims at shortening the time-to-pregnancy, while minimizing the reproductive risks. Knowing which features are associated with the reproductive competence of euploid blastocysts is therefore critical to define, implement, and validate safer and more efficient clinical workflows. Future research should be directed towards: (i) systematic investigations of the mechanisms involved in reproductive aging beyond de novo chromosomal abnormalities, and how lifestyle and nutrition may accelerate or exacerbate their consequences; (ii) improved evaluation of the uterine and blastocyst-endometrial dialogue, both of which represent black boxes themselves; (iii) standardization/automation of embryo assessment and IVF protocols; (iv) additional invasive or preferably non-invasive tools for embryo selection. Only by filling these gaps we may finally crack the riddle behind 'the black box of implantation'.

Development speed of sibling embryo positively reflects live birth rate after fresh day 3 embryo transfer

The ability of sibling embryos to form blastocysts may reflect the developmental potential of the embryos that were transferred into the uterus. The purpose of the study was to investigate whether the development speed of sibling embryos positively reflects the live birth rate following fresh embryo transfer. We examined 1262 cycles of women who underwent day 3 (D3) cleavage embryo transfer in the Peking Union Medical College Hospital in 2015-2020, who were divided into three groups (D5, D5 + D6, and D6) according to blastocyst formation. The live birth rate in patients with blastocysts that formed on D6 was significantly lower than the other two groups (36.1%, 45.6% and 44.7%, P < 0.05). For women with blastocysts that formed on D6, the live birth rate was higher in those with more good quality blastocysts than poor-quality blastocysts (42.4 vs 32.3%, P < 0.05). Multiple regression analysis showed that the blastocyst development speed of sibling embryos was an independent factor affecting live birth after fresh embryo transfer (P < 0.05). We concluded that the blastocyst development speed of sibling embryos may reflect live birth rate following the transfer of D3 cleavage embryos.

Considerations on staffing levels for a modern assisted reproductive laboratory

The duties recently performed in the embryology laboratory have deeply increased compared to those realized a couple of decades ago. Currently, procedures include conventional in vitro fertilization (IVF) and ICSI techniques, or processing of surgically retrieved sperm, embryo culture and time-lapse monitoring, blastocyst culture, as well as trophectoderm biopsy for preimplantation genetic testing and cryopreservation. These techniques require not only time, but also high knowledge level and acutely concentration by the embryologist team. The existing data indicate that an IVF laboratory need to have adequate staffing levels to perform the required daily duties, and to work in optimal conditions that are critical to assure a high quality service, as well as avoiding incidents and to provide the best outcomes. As a result, IVF clinics have invested in human resources, but there is still a large discrepancy between IVF centres on the number of embryologists employed. Currently there is no golden standard on the human resource requirements for assisted reproductive technology procedures; therefore, in this review paper we aim to provide arguments to take into account to determine the embryology staffing requirements in an embryology laboratory to assure optimal safety and efficiency of operations.

Live birth rate following frozen-thawed blastocyst transfer is higher in high-grade day 6 blastocysts than in low-grade day 5 blastocysts

Background

Day 5 (D5) blastocysts are generally given priority to transfer than day 6 (D6) blastocysts; however, which one should be prioritized to transfer when only low-grade D5 and high-grade D6 blastocysts are available?

Methods

A large retrospective cohort study was carried out to evaluate the live birth rate (LBR) following D5 and D6 blastocysts in single frozen-thawed blastocyst transfer (FBT) during January 2014 and December 2018. A multivariate logistic regression was conducted to evaluate the combined impact of expansion day (D5 and D6) and blastocyst quality (high grade/low grade) on LBR, accounting for the potential confounding factors. The biopsied blastocysts from a consecutive PGT-A case series during February 2013 to December 2021 were analyzed in a supplementary study.

Results

The LBR achieved in high-grade D6 blastocyst transfer was significantly higher than that in low-grade D5 blastocyst transfer (50.43% vs. 40.70%, aOR 1.54, 95% CI 1.05-2.26, p = 0.027). There were no significant differences in preterm birth rate, very preterm birth rate, mean live birth weight, and birth weight <1,500 g and >4,000 g between the two cohorts. As for aneuploidy analysis in PGT, there were 54.55% of euploid blastocysts (30/55) among high-grade D6 blastocysts, significantly higher than the 41.39% of euploid blastocysts (565/1,365) among low-grade D5 blastocysts (p < 0.001).

Conclusions

Our data suggest that D6 blastocysts with high morphology grading are preferred than D5 blastocysts with low morphology grading when selecting blastocyst transfer to shorten the time of conception.

Prolonging the time of progesterone supplementation to improve the pregnancy outcomes of single day 6 blastocyst transfer in frozen-thawed cycles: study protocol for a randomized controlled trial

BACKGROUND

Infertility is one of the most important and underappreciated reproductive health problems in developing countries. Currently, in vitro fertilization and embryo transfer is the most effective treatment strategy for infertility. In a frozen-thawed cycle, single-blastocyst transfer can not only ensure relatively higher pregnancy and live birth rates but also effectively reduce the risk of maternal and neonatal complications. In frozen-thawed cycles, progesterone is initiated to promote the final phase of endometrial preparation prior to embryo transfer. However, the optimal duration of exposure to progesterone has remained inconclusive. Therefore, we designed a randomized controlled trial (RCT) to compare the effects of different prolonged progesterone transformation times (P+6 and P+7) on the pregnancy outcomes of D6 single blastocyst transfer in a frozen-thawed cycle.

METHODS

This is a single-center, prospective, randomized controlled clinical trial involving 900 patients with single blastocyst transfer in the frozen-thawed cycle, aged from 20 to 38 years, with less than three transfers, and with HRT-cycle single D6 blastocyst transfer in the current cycle. Participants will be randomly assigned (1:1) into two parallel groups: the transfer of day 6 blastocysts on the 7th day of progesterone supplementation and the transfer of day 6 blastocysts on the 6th day of progesterone supplementation. The primary outcome measure is the clinical pregnancy rate. Secondary outcome measures include the miscarriage rate and live birth rate.

DISCUSSION

This is the first randomized controlled trial to compare the transfer of day 6 blastocysts on the 6th and 7th day of progesterone supplementation. The results of this study will provide evidence for whether to prolong the duration of exposure to progesterone prior to embryo transfer.

TRIAL REGISTRATION

ClinicalTrials.gov, ID: NCT04938011. Registered on 19 June 2021.

Ultralow Oxygen Tension (2%) Is Beneficial for Blastocyst Formation of In Vitro Human Low-Quality Embryo Culture

Objectives

To investigate whether a reduction in the O₂ tension from 5 to 2% during extended culture from day 3 onwards was beneficial to human blastocyst development in vitro.

Methods

We firstly identified 139 patients who had no low-quality embryos on day 3, and all the embryos were prolonged to culture on day 5 or 6. We mainly analyzed 188 patients receiving IVF/ICSI-ET for the first time, and no high-quality embryos were obtained on day 3 from January 2018 to December 2019. After transferred with one or two low-quality embryos, extended culture was performed under low O₂ (5%) or ultralow O₂ (2%) tension for surplus embryos. 296 embryos from 106 patients were continued to culture under 5% O₂ tension, and 214 embryos from 82 patients were continued to culture under 2% O₂ tension. Main outcomes compared were blastulation and high-quality blastulation rates.

Results

We observed no significant differences in the blastulation and high-quality blastulation rates for high-quality cleavage-stage embryos between 2% and 5% O₂ groups (p > 0.05). For low-quality cleavage-stage embryos, we observed that the 2% O₂ group showed a significantly higher blastulation (39.72 versus 31.08%; p = 0.043) rate than that in the 5% O₂ group. The high-quality blastocyst formation rate (10.75 versus 8.45%; p = 0.380) was comparable between the 2% and 5% O₂ groups. The blastulation rate reached 44.86% by culturing blastocysts an additional day under 2% O₂ tension which was significantly higher than that (32.09%) under 5% O₂ tension (p < 0.05).

Conclusion

A reduction in O₂ tension from 5 to 2% after day 3 might be beneficial to the patients with no high-quality embryos. Extended culture to day 7 under 2% O₂ tension increased the number of available blastocysts per IVF/ICSI cycle and was worth recommending especially for patients with few blastocysts.

Oocyte quality and embryo selection strategies: a review for the embryologists, by the embryologists

With the advance of assisted reproduction techniques, and the trend towards blastocyst culture and single embryo transfer, gamete and embryo assessment have gained greater importance in ART treatment. Embryo quality depends mainly on gamete quality and culture conditions. Oocyte maturity identification is necessary in order to plan fertilization timing. Mature oocytes at the metaphase II stage show a higher fertilization rate compared to immature oocytes. Morphology assessment is a critical yet challenging task that may serve as a good prognostic tool for future development and implantation potential if done effectively. Various grading systems have been suggested to assess embryos at pronuclear, cleavage, and blastocyst stages. By identifying the embryo with the highest implantation potential, it is possible to reduce the number of embryos transferred without compromising the chances of a successful pregnancy. Apart from the conventional morphology assessment, there are several invasive or non-invasive methods for embryo selection such as preimplantation genetic testing, morphokinetics, proteomics, metabolomics, oxygen consumption, and measurement of oxidative stress in culture medium. Morphokinetics is a method based on time-lapse technology and continuous monitoring of embryos. In this review, we aim to describe and compare the most effective and widely used methods for gamete and embryo assessment as well as embryo selection.

Comparison of day 5 blastocyst with day 6 blastocyst: Evidence from NGS-based PGT-A results

PURPOSE

Aneuploidy is one genetic factor leading to the failure of embryo implantation. This study aimed to investigate the relationship between the day of embryo blastulation and the ploidy status of embryo, to aid in selecting embryos with the most likelihood of of being euploid in a noninvasive way.

METHODS

This retrospective study recruited women undergoing preimplantation genetic testing (PGT) for aneuploidy (PGT-A) with trophectoderm biopsy from January 2019 to December 2020. The ploidy status of embryos was determined by next-generation sequencing (NGS).

RESULTS

Altogether, 2531 blastocysts from 839 PGT-A cycles were evaluated. The euploid rate of day 5 blastocysts was significantly higher than that of day 6 blastocysts, either from the same ovarian stimulation (OS) cycles (49.9% vs 35.7%, P < 0.001) or from different OS cycles (48.2% vs 27.8%, P < 0.001). This effect of increasing time to embryo blastulation significantly reducing the prevalence of euploidy was not seen in women at age 38 or older. However, after single euploid embryo transfer, the clinical outcomes of day 5 blastocysts were comparable to those of day 6 blastocysts.

CONCLUSIONS

In non-PGT cycles, our data support the selection of day 5 blastocysts for transfer over day 6 blastocysts. Further, women with poor ovarian reserve incline to obtain only day 6 blastocysts, and PGT-A is valuable for identifying the ploidy status of embryos, especially for those with advanced age. However, the stage of blastocysts will not affect the clinical outcome after transfer when they are identified as euploid.

Clinical outcome analysis of frozen-thawed embryo transfer on Day 7

OBJECTIVE

To investigate the clinical outcomes of Day 7 (D7) frozen-thawed embryo transfer (FET) and to provide a reference value for clinical work.

METHODS

This was a retrospective cohort study. Patients undergoing FET cycles in the Reproductive Medicine Center of the Third Affiliated Hospital of Zhengzhou University between December 2015 and January 2021 were included. According to the developmental stage of the embryos at transfer, the embryos were divided into three groups: Day (D) 5, D6 and D7 blastocysts. Group D7 was compared with Groups D5 and D6. Simultaneously, the preimplantation genetic testing (PGT) and non-PGT cycles in Group D7 were analyzed and compared. The main outcomes were the clinical pregnancy, live birth and miscarriage rates. The secondary outcomes were the implantation and euploidy rates.

RESULTS

In total, 5945, 4094 and 137 FET cycles were included in the D5, D6 and D7 groups, respectively. The clinical pregnancy rate was significantly lower in Group D7 than in Groups D5 (13.9% vs 62.9%, P <0.001) and D6 (13.9% vs 51.4%, P <0.001). Additionally, the live birth rate was significantly lower in Group D7 than in Groups D5 (7.3% vs 50.7%, P <0.001) and D6 (7.3% vs 40.5%, P <0.001). However, the miscarriage rate was significantly higher in Group D7 than in Groups D5 (47.4% vs 18.2%, P =0.001) and D6 (47.4% vs 20.6%, P =0.004). The clinical pregnancy and live birth rates for D7 blastocysts were significantly higher in the PGT group than in the non-PGT group (41.7% vs 13.9%, P=0.012; 33.3% vs 7.3%, P =0.003).

CONCLUSIONS

D7 blastocyst transfer can yield a live birth rate that is lower than that for D5 and D6 blastocysts but has value for transfer. PGT for D7 blastocysts may reduce the number of ineffective transfers and improve the outcome of D7 blastocyst transfer, which can be performed according to a patient's situation.

Euploid day 7 blastocysts of infertility patients with only slow embryo development have reduced implantation potential

RESEARCH QUESTION

What is the reproductive potential of embryos that achieve blastulation on day 7 followed by preimplantation genetic testing for aneuploidies (PGT-A) for infertility patients with slow embryo development?

DESIGN

This was a retrospective cohort study in a private IVF clinic of consecutive female infertility patients (n = 2966) aged 24-48 (36.3 ± 3.8) years who underwent frozen embryo transfer (FET) of a single euploid blastocyst.

RESULTS

The women underwent single euploid FET of an embryo that achieved blastulation on day 5 (n = 1880), day 6 (n = 986) or day 7 (n = 100). Day 7 embryos resulted in lower implantation and live birth rates compared with both day 5 and day 6 embryos (P < 0.001). The day 5, day 6 and day 7 groups had 68.5%, 55.2% and 36.0% live birth rates, respectively. The day 7 group was older than the day 5 group (P < 0.001); comparing age-matched cohorts, the day 7 group still had lower implantation and live birth rates (P < 0.0001 and P < 0.001, respectively). Embryo grade was unrelated to live birth rates. Day 7 embryos of expansion grade 5 or 6 or trophectoderm grade A were more likely to be euploid compared with expansion grade 3 or trophectoderm grade B.

CONCLUSIONS

Euploid day 7 embryos represented reduced implantation potential, even when controlling for maternal age. Of all day 7 embryos that underwent PGT-A, euploidy was associated with expansion grade 5 or 6 and trophectoderm grade A. These results can help providers manage patient expectations in cases where infertile women have slow embryo development.

Molecular Drivers of Developmental Arrest in the Human Preimplantation Embryo: A Systematic Review and Critical Analysis Leading to Mapping Future Research

Developmental arrest of the preimplantation embryo is a multifactorial condition, characterized by lack of cellular division for at least 24 hours, hindering the in vitro fertilization cycle outcome. This systematic review aims to present the molecular drivers of developmental arrest, focusing on embryonic and parental factors. A systematic search in PubMed/Medline, Embase and Cochrane-Central-Database was performed in January 2021. A total of 76 studies were included. The identified embryonic factors associated with arrest included gene variations, mitochondrial DNA copy number, methylation patterns, chromosomal abnormalities, metabolic profile and morphological features. Parental factors included, gene variation, protein expression levels and infertility etiology. A valuable conclusion emerging through critical analysis indicated that genetic origins of developmental arrest analyzed from the perspective of parental infertility etiology and the embryo itself, share common ground. This is a unique and long-overdue contribution to literature that for the first time presents an all-inclusive methodological report on the molecular drivers leading to preimplantation embryos’ arrested development. The variety and heterogeneity of developmental arrest drivers, along with their inevitable intertwining relationships does not allow for prioritization on the factors playing a more definitive role in arrested development. This systematic review provides the basis for further research in the field.

Quality of embryos on day 7 after medium refreshment on day 6: a prospective trial

STUDY QUESTION

Are embryos that fail to meet biopsy or freezing criteria on day 6 (D6) more likely to meet these criteria on day 7 (D7) if cultured in fresh medium from D6 to D7?

SUMMARY ANSWER

Refreshment of medium on D6 did not increase the proportion of usable embryos on D7, with an adverse effect for women ≥40 years old.

WHAT IS KNOWN ALREADY

Embryo development in continuous single-step medium, from fertilization to the blastocyst stage, is equivalent to that using a sequential media protocol. However, there remains a theoretical benefit of refreshing the culture environment by transitioning slowly developing D6 embryos to a fresh medium droplet of the same composition, with a renewed source of nutrients and a milieu free of metabolic toxins.

STUDY DESIGN, SIZE, DURATION

This was a prospective trial of culture media exposure in which embryos were randomized on D6 to remain in the same culture medium from D3 to D7 (continuous, n = 620) or be moved to fresh medium (fresh, n = 603) on D6, with re-evaluation on D7. Data were collected from IVF cycles, with or without ICSI, between 29 March 2019 and 17 February 2020.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Embryos from 298 women, aged 18-44 years, from cycles with or without preimplantation genetic testing (PGT) that did not meet criteria for biopsy and/or freeze on D6 were included in the study. Embryos were only included if there was a minimum of two embryos meeting the inclusion criteria in any cohort. Only the first cycle undertaken by each woman in the study period from which embryos were randomized was included.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 1254 embryos were randomized from 312 cycles (209 non-PGT and 103 PGT) including 200 women undergoing IVF without PGT and 98 women who underwent PGT. The proportion of usable blastocysts on D7 did not differ between groups: 10.1% (61/603) in fresh versus 9.7% (60/620) in continuous medium (relative risk (RR) 1.05, 95% CI 0.74-1.47)). Embryos from women ≥40 years old had a significantly decreased likelihood of achieving a usable blastocyst on D7 after culture in fresh versus continuous medium: 3.5% versus 12.2%; RR 0.29, 95% CI 0.08-0.98. In total, 9.9% of embryos otherwise discarded on D6 met the criteria for biopsy and/or freeze on D7.

LIMITATIONS, REASONS FOR CAUTION

Future work investigating implantation, clinical pregnancy and miscarriage rates with D7 embryos is still needed.

WIDER IMPLICATIONS OF THE FINDINGS

Refreshment of medium on D6 did not increase the proportion of usable embryos on D7 overall. Younger women were more likely to develop D7 embryos after refreshment of medium on D6, while an adverse effect was seen in women ≥40 years old. However, by extending the culture of embryos to D7, additional blastocysts become available for clinical use.

STUDY FUNDING/COMPETING INTEREST(S)

Funding was provided through the Department of Obstetrics and Gynecology at Brigham and Women's Hospital. I.G.I. works with Teladoc Health. A.L. has no disclosures. E.S.G. works as a consultant for Teladoc Health, and a writer and editor for UpToDate and BioMed Central. C.R. is a board member of the American Society for Reproductive Medicine and works with UpToDate.

TRIAL REGISTRATION NUMBER

N/A.

When embryology meets genetics: the definition of developmentally incompetent preimplantation embryos (DIPE)-the consensus of two Italian scientific societies

A clear definition of developmentally incompetent preimplantation embryo (DIPE) in literature is still missing, while several scientific societies are discussing this challenging topic. From both a clinical and scientific perspective, the identification of embryos unfit for reproductive purpose is crucial. This aim should be pursued in light of all diagnostic technologies for embryo evaluation, encompassing also genetic analyses, of recent implementation in IVF. The Italian context is characterized by an unusual scenario: embryos can be discarded only if not viable and cannot be used for research purposes either. Therefore, thousands of embryos, diagnosed as affected and/or aneuploid as resulting from preimplantation genetic testing (PGT) and clinically not utilizable, are cryopreserved and stored indefinitely, with important psychological, legal, and financial implications. With the aim of updating the definition of DIPE, also on the basis of the embryo genetic status, the Italian Society of Embryology, Reproduction and Research (SIERR) and the Italian Society of Human Genetic (SIGU) reviewed the literature on this topic, found a consensus, and produced a list of relevant criteria.

Clinical Outcomes Deriving from Transfer of Blastocysts Developed in Day 7: a Systematic Review and Meta-Analysis of Frozen-Thawed IVF Cycles

This meta-analysis aimed to assess the reproductive competence of blastocysts developed on day 7 compared with blastocysts developed on day 5/6. A systematic search was carried out to select relevant studies published before January 2020. Ten retrospective observational cohort studies were included. The primary outcome was the clinical pregnancy rate (CPR). Secondary outcomes were live birth rate (LBR), euploid rate, and survival rates after thawing. Frozen-thawed day 7 blastocyst transfer was associated with a significant reduction in CPR compared to day 5/6 (OR 0.36 95% CI 0.21 to 0.62, p = 0.0002, I² = 71% and OR 0.43, 95% CI 0.32 to 0.58, p < 0.0001, I² = 17% respectively). A significantly lower proportion of LBR was found comparing blastocysts transfers in day 7 to those in day 5/6 (OR 0.21, 95% CI 0.16-0.27, p < 0.0001, I² = 0% and OR 0.34, 95% CI 0.26-0.45, p < 0.0001, I² = 0% respectively). These findings were confirmed in a subgroup of Preimplantation Genetic Testing for Aneuploidies (PGT-A)-screened blastocysts. Blastocysts biopsied in day 7 was associated with a significant decrease of euploid rate compared with day 5/6 (OR 0.47, 95% CI 0.39-0.57, p < 0.0001, I² = 69% and OR 0.68, 95% CI 0.61-0.75, p < 0.0001, I² = 19% respectively). The survival rate after thawing was not statistically different. Sensitivity analyses were also performed. This study shows an association between delayed blastulation and a poorer prognosis in terms of euploid rate and pregnancy outcomes following frozen-thawed transfers. On the other hand, the results do not support the discharge of slow-blastulation embryos.

The dawn of the future: 30 years from the first biopsy of a human embryo. The detailed history of an ongoing revolution

Following early studies showing no adverse effects, cleavage stage biopsy by zona drilling using acid Tyrode's solution, and removal of single blastomeres for preimplantation genetic testing (PGT) and identification of sex in couples at risk of X-linked disease, was performed by Handyside and colleagues in late 1989, and pregnancies reported in 1990. This method was later used for specific diagnosis of monogenic conditions, and a few years later also for chromosomal structural and/or numerical impairments, thereby establishing a valuable alternative option to prenatal diagnosis. This revolutionary approach in clinical embryology spread worldwide, and several other embryo biopsy strategies developed over three decades in a process that is still ongoing. The rationale of this narrative review is to outline the different biopsy approaches implemented across the years in the workflow of the IVF clinics that provided PGT: their establishment, the first clinical experiences, their downsides, evolution, improvement and standardization. The history ends with a glimpse of the future: minimally/non-invasive PGT and experimental embryo micromanipulation protocols. This grand theme review outlines a timeline of the evolution of embryo biopsy protocols, whose implementation is increasing worldwide together with the increasing application of PGT techniques in IVF. It represents a vade mecum especially for the past, present and upcoming operators and experts in this field to (re)live this history from its dawn to its most likely future.

The freeze-all strategy after IVF: which indications?

The freeze-all strategy is gaining popularity worldwide as an alternative to the conventional fresh embryo transfer. It consists of cryopreservation of the entire embryo cohort and the embryo transfer in a subsequent cycle that takes place separately from ovarian stimulation. The freeze-all strategy was initially a 'rescue' strategy for women at high risk of ovarian hyperstimulation syndrome; however, this approach has been extended to other indications as a scheduled strategy to improve implantation rates. This assumes that ovarian stimulation can alter endometrial receptivity in fresh cycles owing to the effect of supraphysiological levels of steroids on endometrial maturation. The procedure, however, has not been associated with increased live birth rates in all infertile couples, and concerns have been raised about the occurrence of several adverse perinatal outcomes. It is, therefore, crucial to identify in which subgroups of patients a freeze-all strategy could be beneficial. The aim of this review is to summarize current scientific research in this field to highlight potential indications for this strategy and to guide clinicians in their daily practice.

What is the reproductive potential of day 7 euploid embryos?

STUDY QUESTION

What is the rate of euploidy and the reproductive potential of embryos biopsied after 6 days of development?

SUMMARY ANSWER

Embryos biopsied after 6 days of development have higher rates of aneuploidy; however, day 7 euploid embryos selected at transfer can achieve acceptable pregnancy rates and live birth (LB) outcomes.

WHAT IS KNOWN ALREADY

Recent publications have shown promising treatment results after euploid day 7 embryo transfers (ETs), albeit these studies were limited by small sample sizes. Whereas the current clinical standard has been to discard embryos that do not reach expansion by day 6 of development, the lack of robust data surrounding the clinical utility of day 7 embryos warrants further evaluation.

STUDY DESIGN, SIZE, DURATION

Retrospective cohort analysis in a single, academic in vitro fertilization (IVF) center from January 2012 to March 2018. A total of 25 775 embryos underwent trophectoderm (TE) biopsy and preimplantation genetic testing for aneuploidy (PGT-A). Additionally, the clinical IVF outcomes of 3824 single, euploid frozen embryo transfer (FET) cycles were evaluated.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Cohorts were segregated by day of TE biopsy following oocyte retrieval (day 5, day 6 or day 7). PGT-A was performed to identify embryonic ploidy rates. Secondly, IVF and LB outcomes after single, euploid FET were evaluated for each cohort.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of day 5 (n = 12 535), day 6 (n = 11 939) and day 7 (n = 1298) embryos were included in the study analysis. The rate of embryo euploidy was significantly lower in day 7 blastocysts compared to day 5 or day 6 cohorts (day 7 = 40.5%; day 5 = 54.7%; day 6 = 52.9%; (P < 0.0001)). After adjusting for age, anti-Müllerian hormone, BMI, embryo quality and number of embryos biopsied, there was a significant association between aneuploidy and embryos biopsied on day 7 when compared to day 5 biopsied embryos (OR = 1.34, CI 95% 1.09-1.45, P = 0.001) and day 6 biopsied embryos (OR = 1.26, CI95% 1.07-1.16, P < 0.001).A sub-analysis of subsequent 3824 single, euploid FET cycles (day 5: n = 2321 cycles; day 6: n = 1381 cycles; and day 7: n = 116 cycles) showed significant differences among cohorts in implantation, clinical pregnancy, LB and clinical loss rates. There was a significant decrease in the odds of implantation, clinical pregnancy and LB, but no association with clinical loss or multiple pregnancy rates in patients who utilized day 7-biopsied embryos during treatment.

LIMITATIONS, REASONS FOR CAUTION

The retrospective nature of the study and potential variability in the study center's laboratory protocol(s) compared to other reproductive treatment centers may limit the external validity of our findings. Additionally, patients who transferred euploid embryos, biopsied on day 7 of development due to an absence of day 5 or day 6 counterparts, may have introduced selection bias in this study.

WIDER IMPLICATIONS OF THE FINDINGS

Embryonic developmental stage, morphological grade and ploidy status are paramount factors affecting ET selection and implantation potential. This study reveals that embryos ineligible for TE biopsy on day 5 or day 6 of development may benefit from extended culture to day 7. Our study demonstrates patient benefit when extended culture to day 7 of development is routinely performed for embryos failing to meet biopsy criteria by day 5 or 6.

STUDY FUNDING/COMPETING INTEREST(S)

No funding was received for the realization of this manuscript. Dr Alan Copperman is Advisor or Board Member of Sema 4 (Stake holder in Data), Progyny and Celmatix.

TRIAL REGISTRATION NUMBER

This retrospective analysis was approved by an Institutional Review Board (WIRB PRO NUM: 20161791; Study Number: 1167398).

Let-7 derived from endometrial extracellular vesicles is an important inducer of embryonic diapause in mice

Embryonic diapause is a maternally controlled phenomenon. The molecule controlling the onset of the phenomenon is unknown. We demonstrated that overexpression of microRNA let-7a or incubation with let-7g-enriched extracellular vesicles from endometrial epithelial cells prolonged the in vitro survival of mouse blastocysts, which developed into live pups after having been transferred to foster mothers. Similar to in vivo dormant blastocysts, let-7-induced dormant blastocysts exhibited low level of proliferation, apoptosis, and nutrient metabolism. Let-7 suppressed c-myc/mTORC1 and mTORC2 signaling to induce embryonic diapause. It also inhibited ODC1 expression reducing biosynthesis of polyamines, which are known to reactivate dormant embryos. Furthermore, the overexpression of let-7 blocked trophoblast differentiation and implantation potential of human embryo surrogates, and prolonged survival of human blastocysts in vitro, supporting the idea that embryonic diapause was an evolutionary conserved phenomenon. In conclusion, let-7 is the main factor inducing embryonic diapause.

Establishment of day 7 blastocyst freezing criteria using blastocyst diameter for single vitrified-warmed blastocyst transfer from live birth outcomes: a single-center, large cohort, retrospectively matched study

PURPOSE

To establish blastocyst freezing criteria for day 7 blastocyst (day 7 BL) for single vitrified-warmed blastocyst transfer (SVBT) by examining the diameter of blastocysts.

METHODS

Patients who underwent day 7 BL transfer cycles (1143 cycles, mean age: 38.5 ± 3.5) and randomly selected patients after 1:1 matching who underwent day 6 BL transfer cycles and day 2-single-embryo transfer (SET) cycles were used for analysis. Comparison of the miscarriage (per clinical pregnancy) and live birth rates were made among day 2-SET, day 7 BL, and day 6 BL. These blastocyst groups were stratified into six groups based on blastocyst diameter, namely, 180 μm, 190 μm, 200 μm, 210 μm, over 220 μm, and hatched, for making the freezing criteria.

RESULTS

For each diameter, 180 μm, 190 μm, 200 μm, 210 μm, over 220 μm, and hatched, the live birth rates of day 7 BL after SVBT were 9.0%, 11.9%, 11.5%, 15.6%, 20.0%, and 19.9%, respectively. Compared with the 14.6% live birth rate of the day 2-SET group, the live birth rate of 220 μm day 7 BL was significantly higher (P < 0.05) and was around the same in other diameter groups.

CONCLUSION

Our study demonstrates that sufficient live birth rates can be obtained after SVBT even from blastocysts on day 7 when blastocysts were vitrified at expanded blastocyst stage of over 180 μm of diameter or at hatched blastocyst stage and were transferred at the optimal time. This is the first study to establish a day 7 blastocyst freezing criteria using blastocyst diameter, which is an objective assessment way.

PROGNOSTIC VALUE OF BLASTOCYST GRADE AFTER FROZEN EUPLOID EMBRYO TRANSFER IN PATIENTS WITH RECURRENT PREGNANCY LOSS

Objective

To determine if trophectoderm (TE) grade or inner cell mass (ICM) grade have predictive value after euploid frozen embryo transfer (euFET) among RPL patients.

Design

Retrospective cohort study.

Setting

Single fertility center, 2012-2018.

Patients

Patients with ≥ 2 prior pregnancy losses performing PGT-A with ≥1 euploid embryo for transfer.

Interventions

All patients underwent ICSI, trophectoderm biopsy, blastocyst grading and vitrification, and single euFET. Outcome of the first transfer was recorded.

Main Outcome Measures

Live birth (LB) and clinical miscarriage (CM) rates.

Results

660 euFET were included. In a binomial logistic regression analysis accounting for age, BMI, AMH and day of blastocyst biopsy, ICM grade C was not significantly associated with odds of live birth (aOR 0.50, 95% CI 0.24-1.02 p=0.057), miscarriage (aOR 1.67, 95% CI 0.56-5.00, p=0.36) or biochemical pregnancy loss (aOR 1.58, 95% CI 0.53-4.75, p=0.42). TE grade C was significantly associated with odds of live birth (aOR 0.49, 95% CI 0.28-0.86, p=0.01) and was not associated with odds of miscarriage (aOR 2.00, 95% CI 0.89-4.47, p=0.09) or biochemical pregnancy loss (aOR 1.85, 95% CI 0.77-4.44, p=0.17). Blastocyst grade CC had significantly lower LB rate compared to all other blastocyst grades (p<0.05, chi-square analysis).

Conclusion

Embryo grade CC and TE grade C are associated with decrease in odds of LB after euFET in RPL patients. Embryo grade is not associated with odds of CM in this cohort of RPL patients, suggesting that additional embryonic or uterine factors may influence risk of pregnancy loss.

Preimplantation Genetic Testing: Where We Are Today

BACKGROUND

Preimplantation genetic testing (PGT) is widely used today in in-vitro fertilization (IVF) centers over the world for selecting euploid embryos for transfer and to improve clinical outcomes in terms of embryo implantation, clinical pregnancy, and live birth rates.

METHODS

We report the current knowledge concerning these procedures and the results from different clinical indications in which PGT is commonly applied.

RESULTS

This paper illustrates different molecular techniques used for this purpose and the clinical significance of the different oocyte and embryo stage (polar bodies, cleavage embryo, and blastocyst) at which it is possible to perform sampling biopsies for PGT. Finally, genetic origin and clinical significance of embryo mosaicism are illustrated.

CONCLUSIONS

The preimplantation genetic testing is a valid technique to evaluated embryo euploidy and mosaicism before transfer.

Tobacco consumption is associated with slow-growing day-6 blastocysts

OBJECTIVE

To investigate if there are any obvious clinical factors associated with delayed blastulation at day 6 (D6) compared with day 5 (D5).

DESIGN

Monocentric observational cohort study from November 2012 to December 2018.

SETTING

Tertiary-care academic medical center.

PATIENTS

A total of 941 women with an entire cohort of exclusively D5 blastocysts compared with 162 patients with a cohort of exclusively D6 blastocysts.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Clinical characteristics and data related to the ovarian stimulation protocols.

RESULTS

After univariate analysis, a significantly higher proportion of women who were active smokers was found in the D6 group compared with the D5 group (n = 22/162 [13.6%] vs. n = 82/941 [8.7%]). In addition, the women in the D6 group had a higher rank number of assisted reproductive technology (ART; total no. of ART cycles performed: 2.1 ± 1.4 vs. 1.6 ± 1.1) and a lower antral follicle count (AFC; 18.7 ± 11.3 vs. 22.2 ± 12.8). Moreover, fertilization with the use of intracytoplasmic sperm injection was used more frequently in the D6 group compared with the D5 group. Logistic regression analysis adjusted for confounders highlighted several independent predictors for reaching blastocyst stage at D6 rather than D5: being an active smoker, previous ART cycles, and a lower AFC.

CONCLUSIONS

Obtaining an exclusively D6 blastocyst cohort is independently associated with women who are active smokers, previous ART cycles, and a lower AFC. These findings provide evidence, to be confirmed by further studies, that women who are active smokers could greatly benefit from smoking cessation before undergoing ART.

Impact of Day 7 Blastocyst Transfer on Obstetric and Perinatal Outcome of Singletons Born After Vitrified-Warmed Embryo Transfer

BACKGROUND

Extended embryo culture has been reported to affect perinatal outcome regarding higher risks of large for gestational age (LGA) and preterm birth (PTB) yet decreased risk of small for gestational age (SGA). However, existing data about the obstetric outcome and the safety for offspring resulting from the transfer of day 7 blastocysts is rare.

OBJECTIVES

To compare obstetric and perinatal outcome using embryos vitrified on day 7 with those vitrified on day 3, day 5, and day 6.

METHODS

Data were collected from 4489 infertile women who gave birth to live-born singletons after vitrified-warmed embryo transfer cycles from January 1, 2006 to December 31, 2017. Singletons were compared depending on the age of embryos. Main perinatal outcome parameters included PTB (gestational age < 37 weeks), very PTB (VPTB, gestational age < 32 weeks), LGA (birthweights > 90th percentiles), and SGA (birthweights < 10th percentiles). Obstetric outcomes included gestational diabetes (GDM), pregnancy-induced hypertension (PIH), preterm premature rupture of membranes (PPROM), pre-eclampsia, placenta previa, placental abruption, and postpartum hemorrhage. Propensity score matching (PSM) was used to adjust the confounding factors across groups and then analyze the association between in vitro culture period and the outcome measures.

RESULTS

After PSM, the transfer of day 7 blastocysts was associated with higher birth weight Z-scores and increased incidence of very large for gestational age (VLGA) compared with the transfer of day 3 cleavage-stage embryos while the incidence of PTB, low birth weight (LBW), SGA did not reach statistical significance. Moreover, comparable perinatal outcome was found in the comparison of day 7 vs. day 5 and day 7 vs. day 6. Day 7 blastocysts did not result in adverse obstetric outcome compared with day 3, day 5, and day 6 embryos, respectively.

CONCLUSION

In vitrified-warmed transfer cycles, day 7 blastocysts were associated with adverse perinatal outcome regarding higher risk of VLGA compared with day 3 cleavage-stage embryo, while blastocysts with diverse growth rates embrace similar developmental viability regardless of blastocysts vitrified on day 5, day 6, or day 7.

Is day 7 culture necessary for in vitro fertilization of cryopreserved/warmed human oocytes?

BACKGROUND

Human embryos are usually cultured to blastocyst stage by Day 5 or 6 after insemination. However, some embryos grow slowly and reach blastocyst stage at Day 7. Acceptable live birth rates have been reported after transfer of Day 7 blastocysts resulted from fresh oocyte in vitro fertilization (IVF). It is unknown whether an extended embryo culture to Day 7 is necessary for cryopreserved oocyte IVF to obtain more transferrable blastocysts.

METHODS

In this study, 455 oocytes from 57 cycles were warmed, inseminated, and the resulting embryos were cultured by Day 7 to examine blastocyst development after extended culture. Fifty one blastocysts from 16 cycles were biopsied to examine embryo aneuploidies.

RESULTS

It was found that 35.1% of the cycles had Day 7 blastocysts, and 3.5% of the cycles had only Day 7 blastocysts. Day 7 blastocysts accounted for 15.6% of total blastocysts. The proportion of top quality of blastocysts was lower at Day 7 than at Day 5 or 6. However, no differences were observed on aneuploid blastocyst rates among Days 5, 6 and 7. Similar clinical pregnancy, ongoing pregnancy and embryo implantation rates were obtained after Day 7 blastocyst transfer as compared with Day 5 or 6 blastocyst transfer.

CONCLUSION

These results indicate that embryos from oocyte warming cycles should be cultured to Day 7 if they do not reach to blastocyst stage by Day 6 so that number of usable blastocysts can be increased.

Busting the myth of extended blastocyst culture until Day 7: Protocol for systematic review and meta-analysis

BACKGROUND

The prolonged culture of embryos to the blastocyst stage represents an increasing procedure in Assisted Reproductive Technology (ART) laboratories. Generally, only blastocysts developing on Day 5 and Day 6 are considered suitable embryos for transfer, cryopreservation or biopsy while embryos developed at a slower rate after Day 6 are routinely discarded. However, also blastocysts developing on Day 7 can be viable and result in a healthy live birth. Unfortunately, data regarding the clinical outcomes of Day 7 blastocysts compared to blastocysts developing on Day 5 or Day 6 are controversial. In this systematic review and aggregate data meta-analysis, we aim to evaluate the real reproductive potential of delayed blastocysts on Day 7 in frozen cycles.

METHODS

We will include all studies, with no restriction regarding the study design (randomized and observational trials, including cohort and case-control), investigating the clinical success of blastocysts developed on Day 7 compared to Day 5 and Day 6 blastocysts. The primary outcomes are the clinical pregnancy rate (CPR) and ongoing pregnancy rate (OPR) following frozen-thawed embryo transfer (Day 7 vs Day 6, and Day 5); secondary outcomes are: live birth rate (LBR) following frozen-thawed embryo transfer, euploid rate and survival rate of thawed blastocyst. Two reviewers independently will judge the methodological quality of studies included in the meta-analysis using the criteria reported in the Cochrane Handbook for Systematic Reviews of Interventions or the Newcastle-Ottawa Scale according to the design of the trials. The meta-analysis will be performed using random effects models and heterogeneity will be assessed using Higgins I2 value. Summary estimate of the proportion of each outcome will be expressed as pooled proportion with 95% confidence interval (CI). The effect of the day on each outcome will be evaluated using a multilevel mixed-effects model with a moderator (the day). The effect will be expressed as odds ratio (OR) with 95% confidence interval (CI). A P value less than .05 will be considered statistically significant.

ETHICS AND DISSEMINATION

This is a systematic review not requiring an ethical approval. Findings derived from this systematic review and meta-analysis will be published in a peer-reviewed journal.

Developmental potential of surplus morulas with delayed and/or incomplete compaction after freezing-thawing procedures

BACKGROUND

Morulas with delayed growth sometimes coexist with blastocysts. There is still limited evidence regarding the optimal disposal of surplus morulas. With the advancement of vitrification, the freezing-thawing technique has been widely applied to zygotes with 2 pronuclei, as well as embryos at the cleavage and blastocyst stages. The freezing of morulas, however, has rarely been discussed. The purpose of this study was to investigate whether these poor-quality and slow-growing morulas are worthy of cryopreservation.

METHODS

This is a retrospective, observational, proof-of-concept study. A total of 1033 day 5/6 surplus morulas were cryopreserved from January 2015 to December 2018. The study included 167 women undergoing 180 frozen embryo transfer cycles. After the morulas underwent freezing-thawing procedures, their development was monitored for an additional day. The primary outcome was the blastocyst formation rate. Secondary outcomes were clinical pregnancy rate, live birth rate and abortion rate.

RESULTS

A total of 347 surplus morulas were thawed. All studied morulas showed delayed compaction (day 5, n = 329; day 6, n = 18) and were graded as having low (M1, n = 54), medium (M2, n = 138) or high (M3, n = 155) fragmentation. The post-thaw survival rate was 79.3%. After 1 day in extended culture, the blastocyst formation rate was 66.6%, and the top-quality blastocyst formation rate was 23.6%. The day 5 morulas graded as M1, M2, and M3 had blastocyst formation rates of 88.9, 74.0, and 52.8% (p < 0.001), respectively, and the top-quality blastocyst formation rates were 64.8, 25.2, and 9.0% (p < 0.001), respectively. The clinical pregnancy rate was 33.6%.

CONCLUSIONS

The post-thaw blastocyst formation rate was satisfactory, with approximately one-half of heavily fragmented morulas (M3) developing into blastocysts. Most of the poor-quality morulas were worth to freeze, with the reasonable goal of obtaining pregnancy and live birth. This alternative strategy may be a feasible approach for coping with poor-quality surplus morulas in non-PGS (preimplantation genetic screening) cycles.

Worth the wait? Day 7 blastocysts have lower euploidy rates but similar sustained implantation rates as Day 5 and Day 6 blastocysts

STUDY QUESTION

Does the reproductive potential of embryos change when blastocyst development takes longer than the traditionally accepted 5 days when accounting for aneuploidy and endometrial-embryo asynchrony?

SUMMARY ANSWER

Aneuploidy increases with increasing duration of blastulation, but if blastocyst morphologic quality and endometrial-embryo asynchrony are controlled for, euploid Day 7 embryos have similar sustained implantation as compared to Days 5 and 6 euploid blastocysts.

WHAT IS KNOWN ALREADY

The relative contributions of diminished embryo quality versus endometrial and embryo asynchrony to poor outcomes associated with embryos cultured past Day 6 are not clear. Asynchrony can be eliminated by embryo vitrification with transfer in a subsequent month after retrieval.

STUDY DESIGN, SIZE, DURATION

Retrospective cohort study of patients from a single center attempting conception through ICSI and utilizing preimplantation genetic testing for aneuploidy screening (PGT-A) from January 2017 to September 2018. Cycles were excluded if they utilized surgical sperm or preimplantation genetic testing for monogenetic/single gene defects. ICSI cycle outcomes from 2586 patients were evaluated for ploidy status of embryos.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Only patients undergoing single, euploid frozen embryo transfer were included when analyzing cycle outcomes by day of blastocyst expansion of the transferred embryo (n = 2130). Ploidy rates by the day upon which an embryo was considered to be usable (denoted, ‘usable blastulation day’) were determined so as to assess the contribution of aneuploidy to slow embryo development. Outcomes of euploid frozen single embryo transfers (SET) of Day 7 embryos were evaluated to assess the reproductive potential associated with embryos that were slowly developing for reasons other than aneuploidy. Analyses were adjusted by maternal age and blastocyst morphology.

MAIN RESULTS AND THE ROLE OF CHANCE

Overall, 67.7% (n = 3508) of usable Day 5 blastocysts were euploid, 52.1% (n = 5560) of usable Day 6 blastocysts were euploid and 43.1% (n = 229) of usable Day 7 embryos were euploid (Day 5 versus Day 6: odds ratio (OR) 0.7 (95% CI, 0.64–0.76), P < 0.001; Day 5 versus Day 7: OR 0.56 (95% CI, 0.46–0.69), P < 0.001; Day 6 versus Day 7: OR 0.81 (95% CI, 0.67–0.99), P = 0.036). Stratified by Society for Assisted Reproductive Technology maternal age groups, a reduction in the prevalence of euploidy by increasing time to embryo blastulation was still seen. The sustained implantation rate (SIR) was similar after euploid SET of Days 5 and 6 embryos (overall, 68.9% (95% CI, 66.0–71.6) and 66.8% (95% CI, 63.8–69.7), respectively; P = 0.81). SIR after euploid Day 7 SET appeared slightly lower than that of Days 5 and 6 embryos (52.6% (95% CI, 35.8–69.0); (Day 5 versus Day 7: OR, 0.67 (95% CI, 0.32–1.41), P = 0.29; Day 6 versus Day 7: OR 0.58 (95% CI, 0.28–1.2), P = 0.14)) but did not achieve statistical significance.

LIMITATIONS, REASONS FOR CAUTION

The primary limitation is the low number of Day 7 blastocyst transfers that limits statistical power. Additionally, the retrospective nature of this study may prevent full elucidation of potential biases with respect to culture, morphologic assessment and selection of Day 7 embryos for transfer.

WIDER IMPLICATIONS OF THE FINDINGS

Routine culture through Day 7 may successfully increase the pool of transferrable embryos for patients who would otherwise have no usable embryos if culture terminated on Day 6. This is particularly true for older patients (i.e. greater than 35 years of age), whose embryos take longer to blastulate and, therefore, are more susceptible to cycle cancelation. Additionally, as evidenced by an adequate overall SIR of 52.6% after euploid SET of Day 7 blastocysts, embryos developing to a usable blastocyst on Day 7 are likely within the ‘window of blastulation.’

STUDY FUNDING/COMPETING INTEREST(S)

None.