The impact of implementing a non-invasive preimplantation genetic testing for aneuploidies (niPGT-A) embryo culture protocol on embryo viability and clinical outcomes

STUDY QUESTION

Are modifications in the embryo culture protocol needed to perform non-invasive preimplantation genetic testing for aneuploidies (niPGT-A) affecting clinical reproductive outcomes, including blastocyst development and pregnancy outcomes?

SUMMARY ANSWER

The implementation of an embryo culture protocol to accommodate niPGT-A has no impact on blastocyst viability or pregnancy outcomes.

WHAT IS KNOWN ALREADY

The recent identification of embryo cell-free (cf) DNA in spent blastocyst media has created the possibility of simplifying PGT-A. Concerns, however, have arisen at two levels. First, the representativeness of that cfDNA to the real ploidy status of the embryo. Second, the logistical changes that need to be implemented by the IVF laboratory when performing niPGT-A and their effect on reproductive outcomes. Concordance rates of niPGT-A to invasive PGT-A have gradually improved; however, the impact of culture protocol changes is not as well understood.

STUDY DESIGN, SIZE, DURATION

As part of a trial examining concordance rates of niPGT-A versus invasive PGT-A, the IVF clinics implemented a specific niPGT-A embryo culture protocol. Briefly, this involved initial culture of fertilized oocytes following each laboratory standard routine up to Day 4. On Day 4, embryos were washed and cultured individually in 10 μl of fresh media. On Day 6 or 7, blastocysts were then biopsied, vitrified, and media collected for the niPGT-A analysis. Six IVF clinics from the previously mentioned trial were enrolled in this analysis. In the concordance trial, Clinic A cultured all embryos (97 cycles and 355 embryos) up to Day 6 or 7, whereas in the remaining clinics (B-F) (379 cycles), nearly a quarter of all the blastocysts (231/985: 23.5%) were biopsied on Day 5, with the remaining blastocysts following the niPGT-A protocol (754/985: 76.5%). During the same period (April 2018-December 2020), the IVF clinics also performed standard invasive PGT-A, which involved culture of embryos up to Days 5, 6, or 7 when blastocysts were biopsied and vitrified.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In total, 428 (476 cycles) patients were in the niPGT-A study group. Embryos from 1392 patients underwent the standard PGT-A culture protocol and formed the control group. Clinical information was obtained and analyzed from all the patients. Statistical comparisons were performed between the study and the control groups according to the day of biopsy.

MAIN RESULTS AND THE ROLE OF CHANCE

The mean age, number of oocytes, fertilization rates, and number of blastocysts biopsied were not significantly different for the study and the control group. Regarding the overall pregnancy outcomes, no significant effect was observed on clinical pregnancy rate, miscarriage rate, or ongoing pregnancy rate (≥12 weeks) in the study group compared to the control group when stratified by day of biopsy.

LIMITATIONS, REASONS FOR CAUTION

The limitations are intrinsic to the retrospective nature of the study, and to the fact that the study was conducted in invasive PGT-A patients and not specifically using niPGT-A cases.

WIDER IMPLICATIONS OF THE FINDINGS

This study shows that modifying current IVF laboratory protocols to adopt niPGT-A has no impact on the number of blastocysts available for transfer and overall clinical outcomes of transferred embryos. Whether removal of the invasive biopsy step leads to further improvements in pregnancy rates awaits further studies.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by Igenomix. C.R., L.N.-S., and D.V. are employees of Igenomix. D.S. was on the Scientific Advisory Board of Igenomix during the study.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov (NCT03520933).

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.

The use of preimplantation genetic testing for aneuploidy: a committee opinion

The use of preimplantation genetic testing for aneuploidy (PGT-A) in the United States has been increasing steadily. Moreover, the underlying technology used for 24-chromosome analysis continues to evolve rapidly. The value of PGT-A as a routine screening test for all patients undergoing in vitro fertilization has not been demonstrated. Although some earlier single-center studies reported higher live-birth rates after PGT-A in favorable-prognosis patients, recent multicenter, randomized control trials in women with available blastocysts concluded that the overall pregnancy outcomes via frozen embryo transfer were similar between PGT-A and conventional in vitro fertilization. The value of PGT-A to lower the risk of clinical miscarriage is also unclear, although these studies have important limitations. This document replaces the document of the same name, last published in 2018.

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.

Blastocysts from partial compaction morulae are not defined by their early mistakes

RESEARCH QUESTION

Is partial compaction during morula formation associated with an embryo's developmental ability and implantation potential?

DESIGN

Retrospective analysis of data from 196 preimplantation genetic testing for aneuploidy (PGT-A) cycles. Embryos starting compaction were grouped according to the inclusion or not of all the blastomeres in the forming morula (full compaction or partial compaction). The possible effect of maternal age and ovarian response on compaction was analysed. Morphokinetic characteristics, blastocyst formation rate, morphology and cytogenetic constitution of the obtained blastocysts were compared. Comparisons of reproductive outcomes after the transfer of euploid blastocysts from both groups were established. Finally, in a subset of embryos, the chromosomal constitution concordance of the abandoned cells and the corresponding blastocyst through trophectoderm biopsies was assessed.

RESULTS

A total of 430 embryos failed to include at least one cell during compaction (partial compaction group [49.3%]), whereas the 442 remaining embryos formed a fully compacted morula (full compaction group [50.7%]). Neither female age nor the number of oocytes collected affected the prevalence of partial compaction morulae. Morphokinetic parameters were altered in embryos from partial compaction morulae compared with full compaction. Although an impairment in blastocyst formation rate was observed in partial compaction morulae (57.2% versus 70.8%, P < 0.001), both chromosomal constitution (euploidy rate: partial compaction [38.4%] versus full compaction [34.2%]) and reproductive outcomes (live birth rate: partial compaction [51.9%] versus full compaction [46.2%]) of the obtained blastocysts were equivalent between groups. A high ploidy correlation of excluded cells-trophectoderm duos was observed.

CONCLUSIONS

Partial compaction morulae show a reduced developmental ability compared with full compaction morulae. Resulting blastocysts from both groups, however, have similar euploidy rates and reproductive outcomes. Cell exclusion might be a consequence of a compromised embryo development regardless of the chromosomal constitution of the excluded cells.

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.

The effects of different endometrial preparation regimens on pregnancy outcomes in frozen-thawed embryo transfer cycles: a prospective randomized controlled study

OBJECTIVE

An increasing number of research have emerged to compare the pregnancy outcomes between the natural cycle and the hormone replacement therapy (HRT) cycle in preparing the endometrium for frozen-thawed embryo transfer (FET), but the results are controversial. This prospective randomized controlled study was hence designed to obtain more solid evidence.

MATERIALS AND METHODS

In this study, patients with regular menstrual cycle length (21-35 days) who underwent FET between January 2010 to December 2017 were recruited for this study. Upon further filtering with the selection criteria of patients being, a total of 405 patients were recruited and randomized. Finally, analysis was performed on 384 patients: 178 belonged to the natural cycle group whereas the remaining 206 were in the HRT group. The primary outcome was live birth rate, while the secondary outcomes were implantation rate, clinical pregnancy rate, early miscarriage rate, late miscarriage rate, multiple birth rate and low birth weight rate.

RESULTS

The live birth rate (37.6% vs 30.1%, p = 0.119) of natural cycle group were higher than those of the hormone replacement therapy group, although the difference was not significant. The secondary outcomes were not found to differ significantly between the two groups. Nonetheless, the endometrium was found to be thicker in the natural cycle group (10.75 mm) than the HRT group (9.00 mm) (p < 0.001).

CONCLUSION

No significant differences were observed between the pregnancy outcomes of the natural cycle group and the HRT group which comprised of patients with regular menstrual cycle length.

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.

Effect of blastocyst shrinkage on assisted reproductive outcomes: a retrospective cohort study describing a new morphological evaluation of blastocyst pre-vitrification and post-warming

BACKGROUND

The failure of frozen-thawed blastocysts to re-expand adequately within a few hours after warming has been reported to have a negative impact on assisted reproductive technology (ART) outcomes. However, the extent to which this failure truly affects ART outcomes has not yet been presented in a manner that is easily understandable to medical practitioners and patients. This study aimed to assess the effects of blastocyst shrinkage on ART outcomes and determine a more effective morphological evaluation approach for use in clinical settings.

METHODS

This retrospective observational cohort study of frozen-thawed blastocyst transfer cycles was conducted from April 2017 to March 2022. Overall, 1,331 cycles were eligible for inclusion, of which 999 were good-quality blastocysts (GQB) and 332 were non-good-quality blastocysts (non-GQB). All frozen-thawed blastocyst transfer cycles performed during the specified study period were included in the study. Exclusion criteria were established to mitigate potential sources of bias as these cycles could impact implantations. We calculated rates and age-adjusted odds ratios of implantation, clinical pregnancy, ongoing pregnancy, and live birth of the re-expansion group, which showed sufficient expansion, and shrinkage group, which showed insufficient expansion. We also calculated the implantation, clinical pregnancy, ongoing pregnancy, and live birth rates of the re-expansion and shrinkage groups for each morphological scoring system parameter.

RESULTS

A reduced ART outcome was observed with use of blastocysts with shrinkage after vitrification/warming. The age-adjusted odds ratios for implantation, clinical pregnancy, ongoing pregnancy, and live birth were lower in the shrinkage group than in the re-expansion group.

CONCLUSIONS

This study examined the adverse effect of blastocyst shrinkage after warming and recovery culturing on reproductive outcomes in a clinically useful manner by retrospectively examining a substantial number of frozen-thawed embryo transfer cycles. The study findings can possibly reduce concerns regarding over- or under-estimation of blastocyst implantation by allowing providers and patients to refer to the data.

Influence of post-thaw culture duration on pregnancy outcomes in frozen blastocyst transfer cycles

In this study, we aimed to evaluate whether post-thaw culture duration affected the clinical outcomes of frozen blastocyst transfer. This retrospective cohort study included 3,901 frozen-thawed blastocyst transfer cycles. The cohorts were divided into two groups based on the developmental stage (day 5 [D5] and day 6 [D6]) and culture duration after thawing (short culture, 2-6 h; long culture, 18-20 h). Women in the short culture group following D6 blastocyst transfer were further divided into three subgroups depending on the post-thaw culture period (2, 4, and 6 h). The main outcomes, namely live birth rate (LBR), implantation rate (IR), clinical pregnancy rate (CPR), and abortion rate (AR), showed no statistical differences within the groups following D5 blastocyst transfer. Patients in the long culture group had significantly lower IR (35.5 vs. 45.8%, p < 0.001), CPR (45.3 vs. 56.6%, p = 0.001), and LBR (35.5 vs. 48.5%, p < 0.001) but a significantly higher AR (21.6 vs. 14.3%, p = 0.049) following D6 blastocyst transfer than those in the short culture group. However, the data failed to present the superiority of any short culture duration over another on the live birth outcome for embryos vitrified on D6 (adjusted odds ratio [aOR]: 0.96, 95% confidence interval [95% CI]: 0.53-1.73, p = 0.881, for the 4-h vs. 2-h subgroup; aOR: 1.01, 95% CI: 0.68-1.49, p = 0.974, for the 6-h vs. 2-h subgroup). Both post-thaw protocols can be applied to patients with D5 blastocysts. To optimize the pregnancy outcomes following D6 blastocyst transfer, a short culture period is recommended. Any of the three short culture durations (2, 4, and 6 h) can be applied, depending on the workflow of the laboratory.

No advantage of single day 6 good-quality blastocyst transfer versus single day 5 poor-quality blastocyst transfer in frozen-thawed cycles stratified by age: a retrospective study

BACKGROUND

Blastocyst developmental speed, morphological grading and patient age are associated with pregnancy outcomes of frozen-thawed cycles. This study aimed to compare the clinical and neonatal outcomes between poor-quality D5 blastocysts and good-quality D6 blastocysts stratified by patient age.

METHODS

A total of 1,623 cycles were divided into two groups: group A (n = 723) received one D5 poor-quality blastocyst; group B (n = 900) received one D6 good-quality blastocyst. Pregnancy and neonatal outcomes were compared among the four groups stratified by 35 years of age.

RESULTS

When patients were in the same age group, there was no significant difference in terms of age, body mass index, infertility duration, infertility type, fertilization method, proportion of endometrial preparation protocols, and endometrial thickness between D5 poor-quality and D6 high-quality blastocysts groups. Live birth rate of D5 poor-quality blastocysts was higher than that of D6 high-quality blastocysts for patients aged < 35 years (35.48% vs. 31.13%, p > 0.05), but there was no statistical difference. The same trend was showed for patients aged ≥ 35 years (29.09% vs. 21.28%, p > 0.05). Moreover, when patients were in the same age category, there was no significant difference in terms of gestational age, birth weight, birth height, and rates of preterm birth, low birth weight, and very low birth weight between groups A and B.

CONCLUSIONS

The preferential selection of poor-quality D5 blastocysts for transfer compared to high-quality D6 blastocysts is recommended, especially for advanced age patients. Single good-quality D6 blastocyst transfer can be considered for the acceptable live birth rate.

Morphological and morphokinetic associations with aneuploidy: a systematic review and meta-analysis

BACKGROUND

A time lapse system (TLS) is utilized in some fertility clinics with the aim of predicting embryo viability and chance of live birth during IVF. It has been hypothesized that aneuploid embryos display altered morphokinetics as a consequence of their abnormal chromosome complement. Since aneuploidy is one of the fundamental reasons for IVF failure and miscarriage, attention has focused on utilizing morphokinetics to develop models to non-invasively risk stratify embryos for ploidy status. This could avoid or reduce the costs associated with pre-implantation genetic testing for aneuploidy (PGT-A). Furthermore, TLS have provided an understanding of the true prevalence of other dysmorphisms. Hypothetically, the incorporation of morphological features into a model could act synergistically, improving a model's discriminative ability to predict ploidy status.

OBJECTIVE AND RATIONALE

The aim of this systematic review and meta-analysis was to investigate associations between ploidy status and morphokinetic or morphological features commonly denoted on a TLS. This will determine the feasibility of a prediction model for euploidy and summarize the most useful prognostic markers to be included in model development.

SEARCH METHODS

Five separate searches were conducted in Medline, Embase, PubMed and Cinahl from inception to 1 July 2021. Search terms and word variants included, among others, PGT-A, ploidy, morphokinetics and time lapse, and the latter were successively substituted for the following morphological parameters: fragmentation, multinucleation, abnormal cleavage and contraction. Studies were limited to human studies.

OUTCOMES

Overall, 58 studies were included incorporating over 40 000 embryos. All except one study had a moderate risk of bias in at least one domain when assessed by the quality in prognostic studies tool. Ten morphokinetic variables were significantly delayed in aneuploid embryos. When excluding studies using less reliable genetic technologies, the most notable variables were: time to eight cells (t8, 1.13 h, 95% CI: 0.21-2.05; three studies; n = 742; I2 = 0%), t9 (2.27 h, 95% CI: 0.5-4.03; two studies; n = 671; I2 = 33%), time to formation of a full blastocyst (tB, 1.99 h, 95% CI 0.15-3.81; four studies; n = 1640; I2 = 76%) and time to expanded blastocyst (tEB, 2.35 h, 95% CI: 0.06-4.63; four studies; n = 1640; I2 = 83%). There is potentially some prognostic potential in the degree of fragmentation, multinucleation persisting to the four-cell stage and frequency of embryo contractions. Reverse cleavage was associated with euploidy in this meta-analysis; however, this article argues that these are likely spurious results requiring further investigation. There was no association with direct unequal cleavage in an embryo that progressed to a blastocyst, or with multinucleation assessed on Day 2 or at the two-cell stage. However, owing to heterogeneous results and poor-quality evidence, associations between these morphological components needs to be investigated further before conclusions can be reliably drawn.

WIDER IMPLICATIONS

This first systematic review and meta-analysis of morphological and morphokinetic associations with ploidy status demonstrates the most useful morphokinetic variables, namely t8, t9 and tEB to be included in future model development. There is considerable variability within aneuploid and euploid embryos making definitively classifying them impossible; however, it is feasible that embryos could be prioritized for biopsy. Furthermore, these results support the mechanism by which algorithms for live birth may have predictive ability, suggesting aneuploidy causes delayed cytokinesis. We highlight significant heterogeneity in our results secondary to local conditions and diverse patient populations, therefore calling for future models to be robustly developed and tested in-house. If successful, such a model would constitute a meaningful breakthrough when accessing PGT-A is unsuitable for couples.

Marginal differences in preimplantation morphokinetics between conventional IVF and ICSI in patients with preimplantation genetic testing for aneuploidy (PGT-A): A sibling oocyte study

Objective

This study aimed to analyze the morphokinetic behaviour between conventional IVF and ICSI, in cycles with preimplantation genetic testing for aneuploidies (PGT-A).

Materials

A randomized controlled trial (NCT03708991) was conducted in a private fertility center. Thirty couples with non-male factor infertility were recruited between November 2018 and April 2019. A total of 568 sibling cumulus oocyte complexes were randomly inseminated with conventional IVF and ICSI and cultured in an Embryoscope time-lapse system. The morphokinetic behaviour of IVF/ICSI sibling oocytes was analysed as primary endpoint. As secondary endpoints, morphokinetic parameters that predict blastocysts that will be biopsied, the day of biopsy, gender and euploid outcome was assessed.

Results

When comparing IVF to ICSI, only the time to reach the 2-cell stage (t2) was significantly delayed for IVF embryos: OR: 1.282 [1.020–1.612], p = 0.033. After standardizing for tPNf (ct parameters), only Blast(tStartBlastulation-t2) remained significant: OR: 0.803 [0.648–0.994], p = 0.044. For the analysis of zygotes that will be biopsied on day 5/6 versus zygotes without biopsy, only early morphokinetic parameters were considered. All parameters were different in the multivariate model: ct2: OR: 0.840 [0.709–0.996], p = 0.045; ct6: OR: 0.943 [0.890–0.998], p = 0.043; cc2(t3-t2): OR: 1.148 [1.044–1.263], p = 0.004; cc3(t5-t3): OR: 1.177 [1.107–1.251], p<0.0001. When comparing the development between blastocysts biopsied on day 5 versus day 6, only three morphokinetic parameters were significant: cc2(t3-t2): OR: 1.394 [1.010–1.926], p = 0.044; ctBlastocyst: OR: 0.613 [0.489–0.768], p<0.0001 and ctExpandedBlastocyst: OR: 0.913 [0.868–0.960], p = 0.0004. Multivariate analysis of gender and ploidy did not reveal differences in morphokinetic behaviour.

Conclusion

Minor morphokinetic differences are observed between IVF and ICSI. Early in the development, distinct cleavage patterns are observed between embryos that will be biopsied or not.

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.

Day 5 vs day 6 single euploid blastocyst frozen embryo transfers: which variables do have an impact on the clinical pregnancy rates?

OBJECTIVE

To determine which variables affect most the clinical pregnancy rate with positive fetal heartbeat (CPR FHB+) when frozen embryo transfer (FET) cycles are performed with day 5 (D5) or day 6 (D6) euploid blastocysts. Design and method A single center retrospective study was performed from March 2017 till February 2021 including all single FET cycles with euploid D5 or D6 blastocysts and transferred in natural cycles (NC) or hormone replacement therapy (HRT) cycles. Trophectoderm (TE) and inner cell mass (ICM) qualities were recorded before biopsy.

RESULTS

A total of 1102 FET cycles were included, 678 with D5 and 424 with D6 blastocysts. Pregnancy rate (PR), clinical PR (CPR), and CPR FHB+ were significantly higher with D5 blastocysts (PR: 70.7% vs 62.0%, OR = 0.68 [0.53-0.89], p = 0.004; CPR: 63.7% vs 54.2%, OR = 0.68 [0.52-0.96], p = 0.002 and CPR FHB+: 57.8% vs 49.8%, OR = 0.72 [0.53-0.96], p = 0.011). However, miscarriage rate (12.5% vs 11.4%, OR = 0.78 [0.48-1.26], p = 0.311) did not differ. From a multivariate logistic regression model, endometrial thickness (OR = 1.11 [1.01-1.22], p = 0.028), patient's age (OR = 1.03 [1.00-1.05], p = 0.021), BMI (OR = 0.97 [0.94-0.99], p = 0.023), and ICM grade C (OR = 0.23 [0.13-0.43], p < 0.001) were significant in predicting CPR FHB+.

CONCLUSION

Although clinical outcomes are higher with D5 blastocysts, CPR FHB+ is more affected by endometrial thickness, patient age, BMI, and ICM grade C rather than biopsy day or endometrial preparation protocol.

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.

First Baby Born in Brazil after Simultaneous Diagnosis through Non-Invasive and Conventional PGT-A

Non-invasive preimplantation genetic testing for aneuploidies (niPGT-A) aiming to assess cell-free embryonic DNA in spent culture media is promising, especially because it might overcome the diminished rates of implantation caused by the inadequate performance of trophectoderm (TE) biopsy. Our center is part of the largest study to date assessing the concordance between conventional PGT-A and niPGT-A, and we report here the delivery of the first baby born in Brazil using niPGT-A. The parents of the baby were admitted to our center in 2018. They did not present history of infertility, and they were interested in using in vitro fertilization (IVF) and PGT-A in order to avoid congenital anomalies in the offspring. A total of 11 (3 day-5 and 8 day-6) expanded blastocysts were biopsied, and the spent culture media (culture from day-4 to day-6) from 8 day-6 blastocysts were collected for niPGT-A. Overall, 7 embryos yielded informative results for trophectoderm (TE) and media samples. Among the embryos with informative results, 5 presented concordant diagnosis between conventional PGT-A and niPGT-A, and 2 presented discordant diagnosis (1 false-positive and one false-negative). The Blastocyst 4, diagnosed as 46, XY by both niPGT-A and conventional PGT-A, was warmed up and transferred, resulting in the birth of a healthy 3.8 kg boy in February 2020. Based on our results and the recent literature, we believe that the safest current application of niPGT-A would be as a method of embryo selection for patients without an indication for conventional PGT-A. The approximate 80% of reliability of niPGT-A in the diagnosis of ploidy is superior to predictions provided by other non-invasive approaches like morphology and morphokinetics selection.

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.

Maternal and neonatal outcomes following blastocyst biopsy for PGT in single vitrified-warmed embryo transfer cycles

RESEARCH QUESTION

Does blastocyst biopsy for preimplantation genetic testing (PGT) increase the risk of adverse maternal and neonatal outcomes?

STUDY DESIGN

Retrospective cohort study of 5097 single vitrified-warmed blastocyst transfer cycles from January 2016 to December 2018, with 2061 cycles in the biopsied group and 3036 cycles in the unbiopsied group enrolled in the analyses. Maternal and neonatal outcomes were compared between the two groups.

RESULTS

The live birth rate in the biopsied group (41.1%) was significantly higher than that in the unbiopsied group (35.6%, adjusted odds ratio [aOR] 1.27, 95% confidence interval [CI] 1.05-1.54, P = 0.012) after adjusting for maternal age, maternal body mass index, gravidity, parity, infertility diagnosis, timing of blastocyst transfer, blastocyst quality, regimen of endometrial preparation, endometrial thickness before transfer and treatment year. The rates of total pregnancy loss (25.4% versus 32.2%, aOR 0.69, 95% CI 0.52-0.91, P = 0.008) and early miscarriage (12.1% versus 17.3%, aOR 0.56, 95% CI 0.38-0.83, P = 0.004) were significantly lower in the biopsied group than in the unbiopsied group. No significant differences were found in sex ratio or the risks of hypertensive disorders in pregnancy, diabetes in pregnancy, placenta previa, preterm premature rupture of membranes, low birthweight, very low birthweight, macrosomia, small for gestational age, large for gestational age or birth defects between the two groups. When the subgroup analyses were conducted based on different types of PGT, similar patterns were found for all types.

CONCLUSION

Blastocyst biopsy might not increase the risks of adverse maternal and neonatal outcomes in the short term.

Effect of age and morphology on sustained implantation rate after euploid blastocyst transfer

RESEARCH QUESTION

What impact does maternal age and embryo morphology have on sustained implantation rates of euploid blastocysts?

DESIGN

This was a retrospective analysis of sustained implantation rates of euploid blastocysts stratified by maternal age and morphology. The primary analysis included 208 embryo transfers with a total of 229 embryos transferred from January 2017 through August 2020.

RESULTS

For all ages the sustained implantation rates for day 5 good quality blastocysts were higher than for day 5 fair, day 5 poor and day 6 blastocysts. At a maternal age of 36 years the best-fit sustained implantation rates were 86% for day 5 good quality blastocysts, 64% for day 5 fair, 63% for day 5 poor, and 51% for all day 6 blastocysts analysed as one group. When controlling for morphology and day of biopsy, there were higher sustained implantation rates for euploid embryos of younger patients compared with older patients. The best-fit sustained implantation rates for age 33 compared to age 39 years were 86% versus 80% for day 5 good, 71% versus 62% for day 5 fair, 59% versus 55% for day 5 poor, and 81% versus 46% for all day 6.

CONCLUSIONS

There was a clinically significant higher sustained implantation rate at all ages for euploid day 5 good quality embryos compared with day 5 fair, day 5 poor and day 6 embryos.

Evaluation of genome-wide DNA methylation profile of human embryos with different developmental competences

STUDY QUESTION

Do embryos with different developmental competence exhibit different DNA methylation profiles at the blastocyst stage?

SUMMARY ANSWER

We established genome-wide DNA methylome analysis for embryo trophectoderm (TE) biopsy samples and our findings demonstrated correlation of methylation profile of trophectoderm with euploidy status and with maternal age, indicating that genome-wide methylation level might be negatively correlated with embryo quality.

WHAT IS KNOWN ALREADY

DNA methylation is a fundamental epigenetic regulatory mechanism that affects differentiation of cells into their future lineages during pre-implantation embryo development. Currently there is no established approach available to assess the epigenetic status of the human preimplantation embryo during routine IVF treatment.

STUDY DESIGN, SIZE, DURATION

In total, we collected trophectoderm biopsy samples from 30 randomly selected human blastocysts and conducted whole-genome bisulfite sequencing (WGBS) to evaluate their DNA methylation profile. Nested linear models were used to assess association between DNA methylation level and ploidy status (aneuploidy [n = 20] vs. euploidy [n = 10]), maternal age (29.4-42.5 years old), and time of blastulation (day 5 [n = 16] vs. day 6 [n = 14]), using embryo identity as a covariate.

PARTICIPANTS/MATERIALS, SETTING, METHODS

TE biopsy samples were obtained and submitted to bisulfite conversion. For WGBS, whole-genome sequencing libraries were then generated from the converted genome. An average of 75 million reads were obtained for each sample, and about 63% of the reads aligned to human reference. An average of 40 million reads used for the final analysis after the unconverted reads were filtered out.

MAIN RESULTS AND THE ROLE OF CHANCE

We revealed an increase of genome-wide DNA methylation level in aneuploid embryo TE biopsies compared to euploid embryos (25.4% ± 3.2% vs. 24.7% ± 3.2%, P < 0.005). We also found genome-wide DNA methylation level to be increased with the maternal age (P < 0.005). On a chromosomal scale, we found monosomic embryos have lower methylation levels on the involved chromosome while no drastic change was observed for the involved chromosome in trisomies. Additionally, we revealed that WGBS data precisely revealed the chromosome copy number variance.

LIMITATIONS, REASONS FOR CAUTION

Though our results demonstrated a negative correlation of genome-wide methylation level and embryo quality, further WGBS analysis on a greater number of embryos and specific investigation of its correlation with implantation and live birth are needed before any practical use of this approach for evaluation of embryo competence.

WIDER IMPLICATIONS OF THE FINDINGS

This study revealed a change in genome-wide DNA methylation profile among embryos with different developmental potentials, reinforcing the critical role of DNA methylation in early development.

STUDY FUNDING/COMPETING INTEREST(S)

No external funding was received for this study. Intramural funding was provided by the Foundation for Embryonic Competence (FEC). E.S. is a consultant for and receives research funding from the Foundation for Embryonic Competence; he is also co-founder and a shareholder of ACIS LLC and coholds patent US2019/055906 issued for utilizing electrical resistance measurement for assessing cell viability and cell membrane piercing.

TRIAL REGISTRATION NUMBER

N/A.

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

STUDY QUESTION

Is there an association between patients' reproductive history and the mean euploidy rates per biopsied blastocysts (m-ER) or the live birth rates (LBRs) per first single vitrified-warmed euploid blastocyst transfers?

SUMMARY ANSWER

Patients' reproductive history (as annotated during counselling) showed no association with the m-ER, but a lower LBR was reported after euploid blastocyst transfer in women with a history of repeated implantation failure (RIF).

WHAT IS KNOWN ALREADY

Several studies have investigated the association between the m-ER and (i) patients' basal characteristics, (ii) ovarian stimulation strategy and dosage, (iii) culture media and conditions, and (iv) embryo morphology and day of full blastocyst development. Conversely, the expected m-ER due to women's reproductive history (previous live births (LBs), miscarriages, failed IVF cycles and transfers, and lack of euploid blastocysts among prior cohorts of biopsied embryos) still needs investigations. Yet, this information is critical to counsel new patients about a first cycle with preimplantation genetic testing for aneuploidy (PGT-A), but even more so after former adverse outcomes to prevent treatment drop-out.

STUDY DESIGN, SIZE, DURATION

This observational study included all patients undergoing a comprehensive chromosome testing (CCT)-based PGT-A cycle with at least one biopsied blastocyst in the period April 2013-December 2019 at a private IVF clinic (n = 2676 patients undergoing 2676 treatments and producing and 8151 blastocysts). m-ER were investigated according to women's reproductive history of LBs: no/≥1, miscarriages: no/1/>1; failed IVF cycles: no/1/2/>2, and implantation failures after previous transfers: no/1/2/>2. Among the 2676 patients included in this study, 440 (16%) had already undergone PGT-A before the study period; the data from these patients were further clustered according to the presence or absence of euploid embryo(s) in their previous cohort of biopsied blastocysts. The clinical outcomes per first single vitrified-warmed euploid blastocyst transfers (n =1580) were investigated according to the number of patients' previous miscarriages and implantation failures.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The procedures involved in this study included ICSI, blastocyst culture, trophectoderm biopsy without hatching in Day 3, CCT-based PGT-A without reporting segmental and/or putative mitotic (or mosaic) aneuploidies and single vitrified-warmed euploid blastocyst transfer. For statistical analysis, Mann-Whitney U or Kruskal-Wallis tests, as well as linear regressions and generalised linear models among ranges of maternal age at oocyte retrieval were performed to identify significant differences for continuous variables. Fisher's exact tests and multivariate logistic regression analyses were instead used for categorical variables.

MAIN RESULTS AND THE ROLE OF CHANCE

Maternal age at oocyte retrieval was the only variable significantly associated with the m-ER. We defined five clusters (<35 years: 66 ± 31%; 35-37 years: 58 ± 33%; 38-40 years: 43 ± 35%; 40-42 years: 28 ± 34%; and >42 years: 17 ± 31%) and all analyses were conducted among them. The m-ER did not show any association with the number of previous LBs, miscarriages, failed IVF cycles or implantation failures. Among patients who had already undergone PGT-A before the study period, the m-ER did not associate with the absence (or presence) of euploid blastocysts in their former cohort of biopsied embryos. Regarding clinical outcomes of the first single vitrified-warmed euploid blastocyst transfer, the implantation rate was 51%, the miscarriage rate was 14% and the LBR was 44%. This LBR was independent of the number of previous miscarriages, but showed a decreasing trend depending on the number of previous implantation failures, reaching statistical significance when comparing patients with >2 failures and patients with no prior failure (36% versus 47%, P < 0.01; multivariate-OR adjusted for embryo quality and day of full blastocyst development: 0.64, 95% CI 0.48-0.86, P < 0.01). No such differences were shown for previous miscarriage rates.

LIMITATIONS, REASONS FOR CAUTION

The sample size for treatments following a former completed PGT-A cycle should be larger in future studies. The data should be confirmed from a multicentre perspective. The analysis should be performed also in non-PGT cycles and/or including patients who did not produce blastocysts, in order to investigate a putative association between women's reproductive history with outcomes other than euploidy and LBRs.

WIDER IMPLICATIONS OF THE FINDINGS

These data are critical to counsel infertile couples before, during and after a PGT-A cycle, especially to prevent treatment discontinuation due to previous adverse reproductive events. Beyond the 'maternal age effect', the causes of idiopathic recurrent pregnancy loss (RPL) and RIF are likely to be endometrial receptivity and selectivity issues; transferring euploid blastocysts might reduce the risk of a further miscarriage, but more information beyond euploidy are required to improve the prognosis in case of RIF.

STUDY FUNDING/COMPETING INTEREST(S)

No funding was received and there are no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

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.

Integrated pseudotime analysis of human pre-implantation embryo single-cell transcriptomes reveals the dynamics of lineage specification

Understanding lineage specification during human pre-implantation development is a gateway to improving assisted reproductive technologies and stem cell research. Here we employ pseudotime analysis of single-cell RNA sequencing (scRNA-seq) data to reconstruct early mouse and human embryo development. Using time-lapse imaging of annotated embryos, we provide an integrated, ordered, and continuous analysis of transcriptomics changes throughout human development. We reveal that human trophectoderm/inner cell mass transcriptomes diverge at the transition from the B2 to the B3 blastocyst stage, just before blastocyst expansion. We explore the dynamics of the fate markers IFI16 and GATA4 and show that they gradually become mutually exclusive upon establishment of epiblast and primitive endoderm fates, respectively. We also provide evidence that NR2F2 marks trophectoderm maturation, initiating from the polar side, and subsequently spreads to all cells after implantation. Our study pinpoints the precise timing of lineage specification events in the human embryo and identifies transcriptomics hallmarks and cell fate markers.

Segmental duplications and monosomies are linked to in vitro developmental arrest

PURPOSE

To verify which genetic abnormalities prevent embryos to blastulate in a stage-specific time.

METHODS

A single center retrospective study was performed between April 2016 and January 2017. Patients requiring Preimplantation Genetic Testing for Aneuploidies (PGT-A) by Next Generation Sequencing (NGS) were included. All embryos were cultured in a time-lapse imaging system and single blastomere biopsy was performed on day 3 of development. Segmental duplications and deletions as well as whole chromosome monosomies and trisomies were registered. Embryo arrest was defined if the embryo failed to blastulate 118 h post-injection. A logistic regression model was applied using the time to blastulate as the response variable and the different mutations as explanatory variables. A p value < 0.05 was considered significant.

RESULTS

Of the 285 biopsied cleavage stage embryos, 103 (36.1%) were euploid, and 182 (63.9%) were aneuploid. There was a significant difference in the developmental arrest between euploid and aneuploid embryos (8.7% versus 42.9%; p = 0.0001). Segmental duplications and whole chromosome monosomies were found to have a significant effect on developmental arrest (p = 0.0163 and p = 0.0075), while trisomies and segmental deletions had no effect on developmental arrest. In case of segmental duplications, an increase of one extra segmental duplication increases the odd of arrest by 159%. For whole chromosome monosomies, the odd will only increase by 29% for every extra chromosomal monosomy. Both chromosomal abnormalities remained significant after adding age as an explanatory variable to the model (p = 0.014 and p = 0.009).

CONCLUSION

Day 3 cleavage stage embryos with segmental duplications or monosomies have a significantly decreased chance to reach the blastocyst stage.

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.

Effect of Embryo Developmental Stage, Morphological Grading, and Ploidy Status on Live Birth Rate in Frozen Cycles of Single Blastocyst Transfer

To determine whether embryo developmental stage or morphological grading can predict live birth rate (LBR) from a single blastocyst in nonbiopsied and biopsied frozen embryo transfer (FET) cycles. This retrospective study included 1336 nonbiopsied and 360 euploid FET cycles. Blastocysts were divided according to developmental stage (day 5 [D5] and day 6 [D6]) and morphology (good quality and low quality). Nonbiopsied cycles in which D5 blastocysts were transferred were associated with a significantly higher LBR than those in the D6 group (48.5 vs. 24.3%; p < 0.001), as well as in good-quality embryo transfer cycles than that in low-quality embryo cycles (52.6 vs. 25.3%; p < 0.001). Embryos reaching good-quality blastocysts on D5 yielded significantly higher LBR than those similar quality blastocysts on D6. The same trend was seen in low-quality embryos. Concerning only D5 or D6 blastocyst transfer, the LBRs of good-quality embryos were still superior to those of low-quality embryos. In the case of euploid embryo transfers, the LBR (48.9 vs. 44.9%, p = 0.444) of D5 blastocysts did not significantly differ from that of D6 blastocysts. Good-quality embryos showed a higher LBR than low-quality embryos (51.6 vs. 40.0%, p = 0.030); the adjusted odds ratio remained insignificant after controlling for confounders (aOR 1.56; 95% CI 0.99-2.45; p = 0.056). The LBRs in the same developmental stage or morphology subgroups were not statistically significant. Embryo developmental stage and morphological grade are useful predictors of LBR in nonbiopsied FET cycles. However, no association was found in euploid transfer cycles.

Multicenter prospective study of concordance between embryonic cell-free DNA and trophectoderm biopsies from 1301 human blastocysts

BACKGROUND

The recent identification of embryonic cell-free DNA in spent blastocyst media has opened a new era of possibilities for noninvasive embryo aneuploidy testing in assisted reproductive technologies. Yet, previous studies assessing a limited number of embryos reported variable concordance between embryonic cell-free DNA and trophectoderm biopsies, thus questioning the validity of this approach.

OBJECTIVE

This study aimed to evaluate the concordance and reproducibility of testing embryonic cell-free DNA vs trophectoderm DNA obtained from the same embryo in a large sample of human blastocysts and to assess the contribution of the inner cell mass and trophectoderm to embryonic cell-free DNA released to the culture media.

STUDY DESIGN

This is an interim analysis of a prospective, observational study among 8 in vitro fertilization centers in 4 continents to assess consistency between noninvasive embryo aneuploidy testing of embryonic cell-free DNA and conventional trophectoderm biopsy. The analysis included 1301 day-6/7 blastocysts obtained in 406 in vitro fertilization cycles from 371 patients aged 20-44 years undergoing preimplantation genetic testing for aneuploidy. Fresh oocytes underwent intracytoplasmic sperm injection or in vitro fertilization. No previous assisted hatching or vitrification was allowed before media collection. Individual spent blastocyst medium was collected from embryos cultured at least 40 hours from day 4. After media collection, conventional preimplantation genetic testing for aneuploidy, comprising trophectoderm biopsy and blastocyst vitrification, was performed. Embryonic cell-free DNA was analyzed blindly after embryo transfer. Inner cell mass and trophectoderm biopsies were also performed in a subset of 81 aneuploid blastocysts donated for research.

RESULTS

Embryonic cell-free DNA analyses were 78.2% (866/1108) concordant with the corresponding trophectoderm biopsies. No significant differences were detected among centers ranging from 72.5% to 86.3%. Concordance rates exceeded 86% when all defined steps in the culture laboratory were controlled to minimize the impact of maternal and operator contamination. Sensitivity per center ranged from 76.5% to 91.3% and specificity from 64.7% to 93.3%. The false-negative rate was 8.3% (92/1108), and false-positive rate was 12.4% (137/1108). The 2 fertilization techniques provided similar sensitivity (80.9% vs 87.9%) and specificity (78.6% vs 69.9%). Multivariate analysis did not reveal any bias from patient clinical background, ovarian stimulation protocols, culture conditions, or embryo quality on testing accuracy of concordance. Moreover, concordances of embryonic cell-free DNA with trophectoderm and inner cell mass suggest that the embryonic cell-free DNA originates from both compartments of the human embryo.

CONCLUSION

Noninvasive analysis of embryonic cell-free DNA in spent blastocyst culture media demonstrates high concordance with trophectoderm biopsy results in this large multicenter series. A noninvasive approach for prioritizing embryo euploidy offers important advantages such as avoiding invasive embryo biopsy and decreased cost, potentially increasing accessibility for a wider patient population.

The hare and the tortoise: extreme mitotic rates and how these affect live birth

RESEARCH QUESTION

Is live birth of patients with excessive slow (no blastocyst on day 5) and fast mitotic rate (full blastocyst development on day 4) comparable to a matched control standard (blastocyst formation on day 5)?

DESIGN

In this retrospective matched (age and anti-Müllerian hormone [AMH]) case-control study rates of fertilization, blastulation, implantation, clinical pregnancy and live birth were compared in couples with male factor indication, prolonged embryo culture and fresh single morula and blastocyst transfer.

RESULTS

The rates of implantation, clinical pregnancy and live birth in the slow-developing group were significantly (P < 0.001) lower (17.6%, 13.7%, and 11.8%, respectively) compared with the fast (58.5%, 52.5%, 47.5%) and normal growing counterparts (51.5%, 42.6%, 39.6%). No differences in neonatal outcome could be observed between the three groups. Sex ratio in the fast-growing group was not different from the other cohorts.

CONCLUSIONS

Extremely slow development, as assessed by the absence of blastulation on day 5, is a negative predictor of pregnancy and live birth. In contrast, the fear that extremely fast-growing embryos may represent an aneuploid cohort of embryos is unsubstantiated. Day-4 full blastocysts can preferentially be considered for transfer.

A stepwise approach to move from a cleavage-stage to a blastocyst-stage transfer policy for all patients in the IVF clinic

STUDY QUESTION

Is a stepwise change management approach an efficacious method to move from a Day 3 transfer policy to a Day 5 transfer policy for all patients in an IVF program?

SUMMARY ANSWER

A stepwise change from a Day 3 to a Day 5 transfer policy maintained the live birth rates per oocyte collection cycle (OCC) of the IVF program, with increased single embryo transfer (SET) and reduction of twin pregnancies.

WHAT IS KNOWN ALREADY

Evidence has shown that the probability of a live birth following IVF with a fresh embryo transfer (ET) is significantly higher after blastocyst-stage transfer than after cleavage-stage transfer. Blastocyst culture and transfer are usually performed in cases of good prognosis patients but many centers keep transferring cleavage-stage embryos for most of their patients because of the higher transfer cancelation rate in a blastocyst transfer policy.

STUDY DESIGN, SIZE, DURATION

In January 2012, a Day 5 embryo culture and blastocyst transfer policy including vitrification of supernumerary Day 5 blastocysts were implemented in a stepwise approach. The retrospective descriptive single-center analysis involving a preintervention phase consisted of Day 3 ETs and Day 3 slow freezing from 2010 until 2012. The postintervention phase involved a 6-year period from 2012 until 2017 in which three consecutive changes in the transfer policy were made, each over a 2-year period, based on the number of zygotes on Day 1. The primary outcome was live birth delivery rate per OCC during the stepwise change.

PARTICIPANTS/MATERIALS, SETTING, METHODS

All patients with at least one zygote available on Day 1 were scheduled for a fresh transfer, either on Day 3 or 5. Cycles with preimplantation genetic testing, freeze-all and oocyte donation cycles and cycles with a Day 2 transfer in the preintervention period were excluded. In the preintervention group, all cycles were scheduled for Day 3 transfer (n = 671 OCC) and slow freezing of the remaining Day 3 embryos. In the postintervention period, three periods were analyzed: period 1 (n = 1510 OCC; 1–9 zygotes: Day 3 transfer and >9 zygotes: Day 5 transfer); period 2 (n = 1456 OCC; 1–4 zygotes: Day 3 transfer and >4 zygotes: Day 5 transfer) and period 3 (n = 1764 OCC; Day 5 transfer). All remaining embryos underwent extend culture and were vitrified on Day 5, if developed to at least an early blastocyst. Data were analyzed using a mixed regression model with patient as a random factor.

MAIN RESULTS AND THE ROLE OF CHANCE

In the preintervention group, all OCC were scheduled for a Day 3 transfer. In period 1, period 2 and period 3, 20.9%, 61.5% and 100% of the OCCs were scheduled for a Day 5 transfer, respectively. More transfers per OCC were canceled in the postintervention period 2 and period 3 compared to the preintervention period (5.3% and 18.7% versus 3.4%, respectively; P < 0.0001). The mean number of embryos used per transfer decreased gradually after the introduction of the Day 5 transfer policy, from 1.62 ± 0.65 in the preintervention group to 1.12 ± 0.61 in period 3 (P < 0.0001). The percentage of SET cycles increased from 48.4% in the preintervention group to 54.6%, 73.8% and 87.8% in period 1, period 2 and period 3, respectively (P < 0.0001). The mean number of cryopreserved surplus embryos was significantly lower in period 3 compared to the preintervention group (1.29 ± 1.97 versus 1.78 ± 2.80; P < 0.0001).

Pregnancy and live birth delivery rate per fresh transfer, respectively, were significantly lower in the preintervention group (26.7% and 19.1%) as compared to period 3 (39.3% and 24.2%) (P < 0.0001). Twin pregnancy rate decreased gradually from 11.0% to 8.2%, 5.7% and 2.5% in the preintervention group, period 1, period 2 and period 3, respectively (P < 0.0001). Live birth rate and cumulative live birth delivery rates per OCC were significantly higher in group 2 compared to the preintervention period (25.6% and 35.8% versus 18.5% and 25.9%, respectively). Similar live birth and cumulative live birth delivery rates per OCC were achieved between the preintervention period and period 3 (18.5% and 25.6% versus 19.7% and 24.9%; respectively).

LIMITATIONS, REASONS FOR CAUTION

The primary limitation is the retrospective design of the study. The allocation of the cycles was done by the number of zygotes available without taking into account both embryological and clinical prognostic factors. Furthermore, the analysis was restricted to cycles where the standard transfer policy was followed. Embryos which were in the morula or compaction stage were not vitrified or cultured to Day 6, which could have contributed to the slight, not statistically significant, drop in live birth rate per OCC in group 3.

WIDER IMPLICATIONS OF THE FINDINGS

Live birth and cumulative live birth delivery rate per OCC in an unselected patient population is maintained in a Day 5 transfer policy compared to a Day 3 transfer policy. Additionally, a significantly reduction in twin pregnancy rate and a significant increase in SET were observed in a Day 5 transfer policy. For centers wanting to make the step from Day 3 to Day 5, this study provides a practical stepwise change management approach.

STUDY FUNDING/COMPETING INTEREST(S)

None.

TRIAL REGISTRATION NUMBER

None.

Transfer the best and biopsy the rest? Blastocyst euploidy rates differ by morphology and day of biopsy

PURPOSE

To determine if blastocyst euploidy rates differ by embryo morphology or day of biopsy.

METHODS

We performed a retrospective analysis of euploidy rates based on patient age, overall embryo morphology grade (good, fair, or poor), and day of biopsy (days 5, 6, or 7) for blastocysts undergoing preimplantation genetic testing for aneuploidy (PGT-A). Our primary analysis included 904 embryos from oocytes age 33-39 years at retrieval.

RESULTS

In our primary analysis, euploidy rates were higher for good quality embryos than poor (64% vs. 48%, p < 0.01) and for fair quality embryos than poor (61% vs. 48%, p < 0.01). There was no significant difference in the euploidy rate between good and fair quality embryos (64% vs. 61%, p = 0.56). Embryos biopsied on day 5 were more likely to be euploid than embryos biopsied on day 6 (59% vs. 50%, p < 0.01) or day 7 (59% vs. 37%, p < 0.01). There was no significant difference in the euploidy rate between day 6 and day 7 embryos (50% vs. 37%, p = 0.07).

CONCLUSION

PGT-A may be more useful in cycles where a lower euploidy rate is expected based on age at oocyte retrieval, embryo morphology, and day of biopsy. There may be little benefit to biopsy of embryos with a high euploidy rate. Young patients with one or more good quality day 5 embryos may benefit from a "transfer the best fresh and biopsy the rest" strategy.

Blasts from the past: is morphology useful in PGT-A tested and untested frozen embryo transfers?

RESEARCH QUESTION

Day of cryopreservation, inner cell mass (ICM) grade, trophectoderm grade and blastocyst expansion grade have been associated with differences in live birth rate in frozen embryo transfer (FET) cycles. This study sought to examine the likelihood of live birth and whether the morphological grade of the blastocyst is more or equally useful in FET cycles among preimplantation genetic testing for aneuploidies (PGT-A) tested and untested blastocysts.

DESIGN

This was a retrospective cohort study of 6271 vitrified-warmed, autologous, single-embryo transfer cycles among patients undergoing IVF from July 2013 to December 2017 at a single, university-affiliated infertility practice. The primary outcome was live birth, calculated by generalized estimating equations.

RESULTS

Among PGT-A tested embryos, inferior ICM grade was associated with a lower chance of live birth (ICM grade B versus A: adjusted risk ratio [aRR] 0.91, 95% confidence interval [CI] 0.84-0.99). Among untested blastocysts there was a lower live birth rate in blastocysts cryopreserved on day 6 versus day 5 (aRR 0.87, 95% CI 0.78-0.96), and those with inferior pre-vitrification trophectoderm grade (trophectoderm grade B versus A: aRR 0.86, 95% CI 0.79-0.94). Blastocysts with a higher pre-vitrification expansion grade (pre-vitrification expansion grade 5 versus 4: aRR 1.1, 95% CI 1.01-1.2) were associated, but ICM grade was not associated (ICM grade B versus A: aRR 0.93, 95% CI 0.86-1.02), with chance of live birth.

CONCLUSIONS

Among PGT-A untested blastocysts, assessing embryo quality by day of cryopreservation, trophectoderm grade and expansion grade may help to identify embryos with the highest likelihood of live birth. Identifying euploid embryos by PGT-A appears to homogenize the cohort, making blastocyst morphological grade and day of cryopreservation less important.

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.

Trophectoderm biopsy for preimplantation genetic test and technical tips: A review

BACKGROUND

Recently, the Japan Society of Obstetrics and Gynecology initiated a clinical study of preimplantation genetic test for aneuploidy. There will be a great need for a standardized embryo biopsy technique in Japan. However, the gold standard trophectoderm (TE) biopsy procedure has not been established, and this review outlines the clinical use of TE biopsy.

METHODS

Based on literature, the method and associated techniques for TE biopsy, a dissection method of TE cells from blastocysts, were investigated.

MAIN FINDINGS

Two TE biopsy methods are used, namely assisted hatching (herniating) and non-assisted hatching (direct suction); however, it is not clear which of these methods is superior. It is critical to understand whether the flicking or pulling method is beneficial.

CONCLUSION

Non-assisted hatching biopsy method may cause blastocyst collapse with a higher probability, and it may extend the biopsy time. The biopsy procedure should be performed within 3 minutes, and thus direct TE suction may have greater disadvantages. It is a fact that pulling method of TE dissection with laser pulse is simple; however, excess laser shots may induce a higher frequency of mosaicism. It is important to understand that each technique of TE biopsy has benefits and disadvantages.

The impact of culture conditions on blastocyst formation and aneuploidy rates: a comparison between single-step and sequential media in a large academic practice

PURPOSE

To compare a single-step medium with a sequential medium on human blastocyst development rates, aneuploidy rates, and clinical outcomes.

METHODS

Retrospective cohort study of IVF cycles that used Sage advantage sequential medium (n = 347) and uninterrupted Sage 1-step medium (n = 519) from July 1, 2016, to December 31, 2017, in an academic fertility center. Main outcome measures are blastocyst formation rates per two-pronuclear (2PN) oocyte and aneuploidy rates per biopsy.

RESULTS

Of all IVF cycles, single-step medium yielded higher blastocyst formation rate (51.7% vs 43.4%) but higher aneuploidy rate (54.0% vs 45.8%) compared with sequential medium. When stratified by maternal age, women under age 38 had no difference in blastocyst formation (52.2% vs 50.2%) but a higher aneuploidy rate (44.5% vs 36.4%) resulting in a lower number of euploid blastocysts per cycle (2.6 vs 3.3) when using single-step medium compared to sequential medium. In cycles used single-step medium, patients ≥ age 38 had higher blastocyst rate (48.0% vs 33.6%), but no difference in aneuploidy rate (68.8% vs 66.0%) or number of euploid embryos (0.8 vs 1.1). For patients reaching euploid embryo transfer, there was no difference in clinical pregnancy rates, miscarriage rates, or live birth rates between two culture media systems.

CONCLUSIONS

Our study demonstrates an increase in aneuploidy in young women whose embryos were cultured in a single-step medium compared to sequential medium. This study highlights the importance of culture conditions on embryo ploidy and the need to stratify by patient age when examining the impact of culture conditions on overall cycle potential.

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.