Comparison of clinical outcomes between single and double vitrified-warmed blastocyst embryo transfer according to the day of vitrification

Effect of postthaw change in embryo score on single euploid embryo transfer success rates

OBJECTIVE

To assess whether the change in embryo morphology from precryopreservation to postthaw is associated with the embryo transfer success rates in single euploid embryo transfer cycles.

DESIGN

Retrospective cohort study.

SETTING

Academic affiliated fertility clinic.

PATIENT(S)

Patients who underwent a single euploid embryo transfer cycle from September 2016 to April 2022 were included. A decision support tool was used to assign each embryo a reproductive potential score on the basis of the day of biopsy, expansion, and grade of trophectoderm and inner cell mass at the time of cryopreservation and after thaw. Embryos were divided into 4 groups: group 1 included embryos with the same score after thaw (reference); group 2 included those with a higher score; group 3 included those with a lower score; and group 4 included those that did not re-expand after thaw.

INTERVENTION(S)

No interventions administered.

MAIN OUTCOME MEASURE(S)

The primary outcome was the live birth rates (LBRs) per embryo transfer. The secondary outcomes included the chemical pregnancy, clinical pregnancy, and clinical pregnancy loss rates. Comparative statistics and univariate analyses were performed using the Kruskal-Wallis and χ2tests. Multivariate logistic regression fitted with generalized estimating equation was performed to compare the odds of live birth between groups.

RESULT(S)

A total of 7,750 embryo transfers performed for 4,613 patients met inclusion criteria: 5,331 in group 1; 486 in group 2; 1,726 in group 3; and 207 in group 4. In the univariate analysis, there was a statistically significant difference in the LBR between groups 1, 2, 3, and 4 (55.8% vs. 51.4%, 47.5%, and 26.6%). Logistic regression controlling for oocyte age, antimüllerian hormone, body mass index, endometrial thickness, year of embryo transfer, time from thaw to final grading, and embryo score before cryopreservation showed significantly lower odds of live birth when the embryo was downgraded (odds ratio [OR], 0.70; confidence interval [CI], 0.62-0.79) or did not re-expand (OR, 0.36; CI, 0.26-0.51) than those with no change in score. When controlling for all variables, there was a significant increase in the odds of live birth between embryos that had a higher score after thaw and those without a change (OR, 1.42; CI, 1.14-1.76). There was no significant difference in the clinical pregnancy loss rate among the 4 groups.

CONCLUSION(S)

The change in the quality of the embryo after thaw is an important factor in embryo transfer success. In an adjusted analysis, the chemical and clinical pregnancy rates and LBR per embryo transfer all significantly decrease in embryos that were downgraded or did not expand on the day of single euploid embryo transfer. Embryos that re-expand and have improved quality after thaw have the highest odds of live birth.

Effect of repeated vitrification of human embryos on pregnancy and neonatal outcomes

BACKGROUND

Repeated cryopreservation of embryos should occasionally be considered when embryos were not suitable for transfer. The effect of re-cryopreservation on embryos remains contentious.

METHODS

This retrospective cohort study aimed to evaluate the pregnancy and neonatal outcomes of twice vitrificated blastocyst derived from once vitrified embryos. Total 410 vitrified-warmed blastocyst transfer cycles were divided into two groups according to the times of embryo vitrification: (1) vitrified blastocysts derived from fresh blastocysts (control group, n = 337); (2) twice vitrified blastocysts derived from once vitrified embryos (n = 73). The primary outcome was live birth rate. Multivariable logistic or linear regression analysis model was performed to describe the association between embryo cryopreservation times and clinical outcomes.

RESULTS

No difference was observed in female age at retrieval and transfer, infertility period, body mass index (BMI), infertility type, endometrial thickness, and embryo transfer numbers between the two groups. The pregnancy outcomes of embryos in repeated cryopreservation group were comparable to those of embryos in control group, including implantation rate, clinical pregnancy rate, and live birth rate. In multivariate logistic regression analysis, the cryopreservation times did not affect the outcomes of biochemical pregnancy, clinical pregnancy, and live birth. Moreover, there was no difference in gestational age, birthweight and sex ratio of singleton newborns between groups. After correcting several possible confounding variables, no significant association was observed between cryopreservation times and neonatal birthweight.

CONCLUSION

In conclusion, pregnancy and neonatal outcomes achieved with twice vitrified blastocyst transfer were comparable to those achieved with vitrified blastocyst transfer in control group.

Comparing Day 5 versus Day 6 euploid blastocyst in frozen embryo transfer and developing a predictive model for optimizing outcomes: a retrospective cohort study

Background

Optimal protocols for frozen-thawed embryo transfer (FET) after preimplantation genetic testing (PGT) remain unclear. This study compared Day 5 (D5) and Day 6 (D6) blastocysts and evaluated predictors of FET success.

Methods

A total of 870 patients with genetic diseases or chromosomal translocations who received PGT at the First Affiliated Hospital of Zhengzhou University from January 2015 to December 2019 were recruited. All patients underwent at least one year of follow-up. Patients were divided into groups according to the blastocyst development days and quality. Univariate and multivariate logistic regression were applied to identify risk factors that affect clinical outcomes and to construct a predictive nomogram model. Area under the curve (AUC) of the subject's operating characteristic curve and GiViTI calibration belt were conducted to determine the discrimination and fit of the model.

Results

D5 blastocysts, especially high-quality D5, resulted in significantly higher clinical pregnancy (58.4% vs 49.2%) and live birth rates (52.5% vs 45%) compared to D6. Multivariate regression demonstrated the number of blastocysts, endometrial preparation protocol, days of embryonic development and the quality of blastocysts independently affected live birth rates (P<0.05). A nomogram integrating these factors indicated favorable predictive accuracy (AUC=0.598) and fit (GiViTI, P=0.192).

Conclusions

Transferring high-quality D5 euploid blastocysts after PGT maximizes pregnancy outcomes. Blastocyst quality, blastocyst development days, endometrial preparation protocols, and number of blastocysts, independently predicted outcomes. An individualized predictive model integrating these factors displayed favorable accuracy for counseling patients and optimizing clinical management.

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.

Prediction of embryo implantation rate using a sole parameter of timing of starting blastulation

A time-lapse monitoring system provides a complete picture of the dynamic embryonic development process and simultaneously supplies extensive morphokinetic data. The objective of this study was to investigate whether the use of the morphokinetic parameter of time of starting blastulation (tSB) can improve the implantation rate of day-5 transferred blastocyst selected based on morphological parameters. In this retrospective study we analyzed the morphokinetics of 196 day-5 transferred blastocysts, selected solely based on morphological parameters. The interval time from intracytoplasmic sperm injection (ICSI) to time of starting blastocyst formation (tSB) was calculated for each embryo. The overall implantation rate of transferred blastocyst, selected based only on morphological parameters, was 49.2%. Implantation rate, determined retrospectively, was significantly higher (58.8% versus 42.6%, P = 0.02) for embryos with a short interval time to tSB (78-95.9 h) compared with embryos with a longer timeframe (96-114 h). Time of expanded blastocyst (tEB) post-ICSI was also significantly associated with implantation; however, this parameter was not available for all the embryos at time of transfer. When we tested only high ranked KIDScore day-3 sub-group embryos, the implantation rate was significantly higher in short interval time embryos compared with longer interval time embryos (62.2% vs. 45.5%, respectively, P = 0.02).These observations emphasize the importance of the timing of starting blastulation over blastocyst morphological parameters and may provide a preferable criterion for good morphology day-5 blastocyst selection.

Pregnancy outcomes after day 5 versus day 6 blastocyst-stage embryo transfer: A systematic review and meta-analysis

AIM

To compare the pregnancy outcomes after day 5 blastocyst-stage embryo transfers (BET) versus day 6 BET following vitrified-warmed cycle and to evaluate whether the number of embryos transferred and the chromosomal status of embryo influence effect estimates.

METHODS

A literature search (PubMed, Embase and MEDLINE) up to January 2019 was conducted to identify studies where women with day 6 BET were compared to women with day 5 BET. Only studies published in English language, on peer-reviewed journal were considered eligible. The following subgroup analyses were performed: (i) number of embryos transferred and (ii) chromosomal status of embryo.

RESULTS

From a total of 1956 articles identified, 23 observational studies were included in the meta-analysis. We observed that day 6 BET were associated with lower implantation rate (risk ratio, RR: 1.17, 95% confidence interval, CI: 1.10-1.24), clinical pregnancy rate (RR: 1.17, 95% CI: 1.10-1.24), ongoing pregnancy rate (RR: 1.15, 95% CI: 1.07-1.24) and live birth rate (RR: 1.22, 95% CI: 1.11-1.33) than day 5 BET following vitrified-warmed cycle. The subgroup analysis found that the superiority of day 5 BET compared with day 6 BET is influenced by the number of embryos transferred and chromosomal status of embryos.

CONCLUSION

Current evidence shows that day 5 BET is superior to day 6 BET following vitrified-warmed cycle in clinical practice. Due to the overall low quality of available evidence, more larger and well-conducted studies are needed to compare the pregnancy outcomes between day 5 and day 6 BET before drawing a clear conclusion.

Obstetric, Neonatal, and Clinical Outcomes of Day 6 vs. Day 5 Vitrified-Warmed Blastocyst Transfers: Retrospective Cohort Study With Propensity Score Matching

Despite the large number of studies on blastocyst transfers, it is unclear whether day 6 blastocysts have similar pregnancy rates and safety with day 5 blastocysts. Thus, this study aimed to compare the obstetric, neonatal, and clinical outcomes of day 5 and day 6 vitrified blastocyst transfers (VBT). In this retrospective cohort study with propensity score matching, we evaluated 1,313 cycles of VBT performed between January 2014 and December 2015 at the Fertility Center of CHA Gangnam Medical Center. All cycles underwent natural endometrial preparation. We used propensity score matching to compare day 5 and day 6 VBTs in a matched comparison. After propensity score matching, there were 465 cycles of day 5 VBT and 155 cycles of day 6 VBT. Implantation rate (IR), clinical pregnancy rate (CPR), and live birth rate (LBR) were significantly lower in day 6 VBTs (44.2 vs. 53.1%, p = 0.023; 48.4 vs. 60.4%, p = 0.009; 33.5 vs. 51.8%, p < 0.001). Miscarriage rate was significantly higher in day 6 VBTs (29.3 vs. 10.7%, p < 0.001). Rate of multiple gestations was similar between the two groups (29.3 vs. 30.2%, p = 0.816). Assessing 241 and 52 babies from day 5 and day 6 VBTs, no differences were found in neonatal outcomes including rates of low birth weight, preterm birth, and congenital malformations. In propensity score-matched analysis, obstetric, and neonatal outcomes between day 5 and day 6 VBTs were similar so that day 6 VBTs are as safe as day 5 VBTs. IR, CPR, and LBR were are all significantly lower in day 6 VBTs. Therefore, if there are no differences in the morphological grade between day 5 and day 6 blastocysts, transfer of day 5 vitrified blastocysts should be considered first.

Day 5 versus Day 6 blastocyst transfers: a systematic review and meta-analysis of clinical outcomes

STUDY QUESTION

Is there a difference in clinical pregnancy and live birth rates (LBRs) between blastocysts developing on Day 5 (D5) and blastocysts developing on Day 6 (D6) following fresh and frozen transfers?

SUMMARY ANSWER

D5 blastocyst transfers (BTs) present higher clinical pregnancy and LBRs than D6 in both fresh and frozen transfers.

WHAT IS KNOWN ALREADY

BT is increasingly popular in assisted reproductive technology (ART) centers today. To our knowledge, no meta-analysis has focused on clinical outcomes in both fresh and frozen BT. Concerning frozen blastocysts, one meta-analysis in 2010 found no significant difference in pregnancy outcomes between D5 and D6 BT. Since then, ART practices have evolved particularly with the wide use of vitrification, and more articles comparing D5 and D6 BT cycles have been published and described conflicting results.

STUDY DESIGN, SIZE, DURATION

Systematic review and meta-analysis of published controlled studies. Searches were conducted from 2005 to February 2018 on MEDLINE and Cochrane Library and from 2005 to May 2017 on EMBASE, Eudract and clinicaltrials.gov, using the following search terms: blastocyst, Day 5, Day 6, pregnancy, implantation, live birth and embryo transfer (ET).

PARTICIPANTS/MATERIALS, SETTING, METHODS

A total of 47 full-text articles were preselected from 808 references, based on title and abstract and assessed utilizing the Newcastle-Ottowa Quality Assessment Scales. Study selection and data extraction were carried out by two independent reviewers according to Cochrane methods. Random-effect meta-analysis was performed on all data (overall analysis) followed by subgroup analysis (fresh, vitrified/warmed, slow frozen/thawed).

MAIN RESULTS AND THE ROLE OF CHANCE

Data from 29 relevant articles were extracted and integrated in the meta-analysis. Meta-analysis of the 23 studies that reported clinical pregnancy rate (CPR) as an outcome, including overall fresh and/or frozen ET cycles, showed a significantly higher CPR following D5 ET compared with D6 ET (risk ratio (RR) = 1.27, 95% CI: 1.15-1.39, P < 0.001). For CPR, calculated subgroup RRs were 2.38 (95% CI: 1.74-3.24, P < 0.001) for fresh BT; 1.27 (95% CI: 1.16-1.39, P < 0.001) for vitrified/warmed BT; and 1.15 (95% CI: 0.93-1.41, P = 0.20) for slow frozen/thawed BT. LBR was also significantly higher after D5 BT (overall RR = 1.50 (95% CI: 1.32-1.69), P < 0.001). The LBR calculated RRs for subgroups were 1.74 (95% CI: 1.37-2.20, P < 0.001) for fresh BT; 1.38 (95% CI: 1.23-1.56, P < 0.001) for vitrified/warmed BT; and 1.44 (95% CI: 0.70-2.96, P = 0.32) for slow frozen/thawed BT. Sensitivity analysis led to similar results and conclusions: CPR and LBR were significantly higher following D5 compared to D6 BT.

LIMITATIONS, REASONS FOR CAUTION

The validity of meta-analysis results depends mainly on the quality and the number of the published studies available. Indeed, this meta-analysis included no randomized controlled trial (RCT). Slow frozen/thawed subgroups showed substantial heterogeneity.

WIDER IMPLICATIONS OF THE FINDINGS

In regards to the results of this original meta-analysis, ART practitioners should preferably transfer D5 rather than D6 blastocysts in both fresh and frozen cycles. Further RCTs are needed to address the question of whether D6 embryos should be transferred in a fresh or a frozen cycle.

STUDY FUNDING/COMPETING INTEREST(S)

This work was sponsored by an unrestricted grant from GEDEON RICHTER France. The authors have no competing interests to declare.

REGISTRATION NUMBER

CRD42018080151.

Pregnancy rates for single embryo transfer (SET) of day 5 and day 6 blastocysts after cryopreservation by vitrification and slow freeze

PURPOSE

The purpose of this study was to compare clinical and ongoing pregnancy rates in cycles with single embryo transfer (SET) of blastocysts cryopreserved on day 5 or day 6. Our aim was to determine whether day 6 blastocysts perform adequately to recommend SET.

METHODS

Retrospective cohort study including 468 transfer cycles for 392 women younger than age 38 undergoing SET at a university-affiliated IVF clinic in the USA. A total of 261 day 5 blastocysts and 207 day 6 blastocysts for frozen-thawed SET between 2010 and 2016 were analyzed. Data included cryopreservation by both a slow freeze method and vitrification.

RESULTS

In total, 59.0% of day 5 SET cycles resulted in a clinical pregnancy compared to 54.1% of day 6 blastocysts (p = 0.54). Ongoing pregnancy rates from day 5 frozen-thawed blastocysts (51.7%) were comparable to day 6 (44.9%, p = 0.14). When looking at vitrified blastocysts only, there were no significant differences between day 5 and day 6 blastocysts, with a clinical pregnancy rate of 69.2% for day 5 and 72.5% for day 6 (p = 0.68).

CONCLUSIONS

SETs of day 6 cryopreserved blastocysts resulted in similar clinical and ongoing pregnancy rates compared to day 5, particularly after vitrification.

Efficacy of hyaluronan-rich transfer medium on implantation and pregnancy rates in fresh and frozen-thawed blastocyst transfers in Korean women with previous implantation failure

Objective

To evaluate the effect of hyaluronan-rich transfer medium on pregnancy and implantation rates in fresh and frozen-thawed embryo transfers in Korean women with previous implantation failure.

Methods

This retrospective study included 283 blastocyst transfers in patients with previous embryo transfer failure at a private fertility clinic. In the study group (n=88), blastocyst transfers were performed using an hyaluronan-rich transfer medium prior to transfer, whereas blastocyst transfers without any treatment served as controls (n=195). According to the type of transfer (fresh elective or frozen-thawed), all the blastocyst transfers were divided into two study and two control groups.

Results

The patient's mean age, serum anti-Müllerian hormone level, causes of infertility, embryo quality, and the number of transferred embryos were comparable between the study and control groups. There were no significant differences in clinical pregnancy rate (45.5% vs. 43.1%), implantation rate (28.9% vs. 28.8%), and clinical abortion rate (10.0% vs. 8.3%) between the two groups, and these findings were not changed after subgroup analysis according to the type of transfer.

Conclusion

The use of hyaluronan-rich transfer medium in the blastocyst transfer does not appear to have any significant effect on the implantation and pregnancy rates in patients with previous implantation failure.

[Comparison of frozen embryo transfer outcomes at blastocyst stage according to freezing method and type of endometrial preparation]

OBJECTIVE

This study intended to compare frozen embryo transfer (FET) outcomes at blastocyst stage according to freezing methods, slow freezing versus vitrification and according to the type of endometrial preparation.

PATIENTS AND METHODS

A total of 172 FET at blastocyst stage (day 5 or 6) were included retrospectively from April, 2007 to December, 2012. The FET outcomes from slow freezing (group 1, n=86) were compared with those from vitrification (group 2, n=86). More particularly, the survival rate after thawing, as well as implantation and pregnancy rates (clinical and ongoing pregnancy rates) were compared respectively between these two groups, after matching on women's age at freezing day, embryo number and embryo development stage for transfer. Furthermore, for each freezing method, FET outcomes were compared according to the type of endometrial preparation, i.e. natural cycle (group N) versus stimulated cycle (group S).

RESULTS

The survival rate as well as implantation and clinical pregnancy rates were significantly higher for FET after vitrification compared to FET after slow freezing (97% vs 85%, P<0.0001; 32% vs 20%, P=0.02; 43% vs 28%, P=0.04, respectively). By taking into account the number of transferred embryos for each group, the multiple pregnancy rate was three-fold higher in the group of FET after vitrification compared to the group of FET after slow freezing but not significantly (27.3% vs 8.3%, NS). However, FET outcomes were not affected significantly by the type of endometrial preparation whatever freezing methods. Nevertheless, the early spontaneous abortion (ESA) rate was lower in the case of embryos that were frozen by vitrification and transferred in natural cycle (group N2 vs group S2: 20% vs 47%, NS).

DISCUSSION AND CONCLUSION

Our study confirms that the survival rate after thawing at blastocyst stage (day 5 or 6) is significantly improved after freezing by vitrification compared to slow freezing method. Likewise, implantation and clinical pregnancy rates are significantly increased in the case of FET at blastocyst stage when these embryos were frozen by vitrification. The results obtained by vitrification are very satisfactory but are also associated with an increased multiple pregnancy rate. Moreover, FET associated with natural or stimulated cycle does not modify significantly the outcomes of attempts, whatever the freezing method. However, the risk of ESA is reduced in the case of FET with natural cycle and after embryo vitrification.