Comparison of differences in development potentials between frozen-thawed D5 and D6 blastocysts and their relationship with pregnancy outcomes

Impact of different progesterone timings on live birth rates for blastocyst frozen embryo transfer cycles

RESEARCH QUESTION

Do different timings of progesterone administration for day 5 and day 6 blastocysts affect the live birth rate (LBR) of artificial frozen embryo transfer (FET) cycles?

DESIGN

This retrospective cohort study included 1362 patients who underwent artificial FET cycles. The effects of 6 and 7 days of progesterone administration prior to blastocyst transfer on clinical outcomes were compared in day 5 and day 6 blastocysts. Univariable and multivariable regression analyses were undertaken.

RESULTS

In all patients, LBR was comparable between the two groups (51.8% versus 47.9%, P = 0.165). For day 6 blastocysts, after adjusting for confounders, the 7-day progesterone regimen resulted in a significantly higher LBR (44.8% versus 36.4%, P = 0.039, adjusted OR = 1.494, 95% CI 1.060-2.106) and lower pregnancy loss rate (15.4% versus 25.2%, P = 0.031, adjusted OR = 0.472, 95% CI 0.260-0.856) compared with the 6-day progesterone regimen. For day 5 blastocysts, there were no significant differences in pregnancy outcomes between the two regimens, but the rate of low birthweight was higher with the 7-day progesterone regimen than with the 6-day progesterone regimen (13.9% versus 6.7%, P = 0.032).

CONCLUSIONS

In all blastocyst analyses, no difference in LBR was found between the 6- and 7-day progesterone regimens in artificial FET cycles. For day 6 blastocysts, LBR was significantly higher with the 7-day progesterone regimen than with the 6-day progesterone regimen, whereas for day 5 blastocysts, pregnancy outcomes were comparable between the two regimens.

Developing and validating a prediction model of live birth following single vitrified-warmed blastocyst transfer

RESEARCH QUESTION

Can the developed clinical prediction model offer an accurate estimate of the likelihood of live birth, involving blastocyst morphology and vitrification day after single vitrified-warmed blastocyst transfer (SVBT), and therefore assist clinicians and patients?

STUDY DESIGN

Retrospective cohort study conducted at a Spanish university-based reproductive medicine unit (2017-2021) including consecutive vitrified-warmed blastocysts from IVF cycles. A multivariable logistic regression incorporated key live birth predictors: vitrification day, embryo score, embryo ploidy status and clinically relevant variables, i.e. maternal age.

RESULTS

The training set involved 1653 SVBT cycles carried out between 2017 and 2020; 592 SVBT cycles from 2021 constituted the external validation dataset. The model revealed that female age and embryo characteristics, including overall quality and blastulation day, is linked to live birth rate in SVBT cycles. Stratification by vitrification day and quality (from day-5A to day-6 C blastocysts) applied to genetically tested and untested embryos. The model's area under the curve was 0.66 (95% CI 0.64 to 0.69) during development and 0.65 (95% CI 0.61 to 0.70) in validation, denoting moderate discrimination. Calibration plots showed strong agreement between predicted and observed probabilities.

CONCLUSION

By incorporating essential predictors such as vitrification day, embryo morphology grade, age and preimplantation genetic testing for aneuploidy usage, this predictive model offers valuable guidance to clinicians and patients, enabling accurate forecasts of live birth rates for any given vitrified blastocyst within SVBT cycles. Additionally, it serves as a potentially indispensable laboratory tool, aiding in selecting the most promising blastocysts for optimal outcomes.

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.

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.

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.

D6 high-quality expanded blastocysts and D5 expanded blastocysts have similar pregnancy and perinatal outcomes following single frozen blastocyst transfer

Objective

We compared the pregnancy and perinatal outcomes between expanded blastocysts vitrified on D5 versus D6 following single frozen blastocyst transfer.

Methods

Clinical data on 7,606 cycles of frozen-thawed blastocyst implantations were retrospectively analyzed. Depending on whether blastocysts were vitrified on D5 or D6 and the transferred blastocysts, the blastocysts were divided into 6 groups: HQB-D5, HQB-D6, 4XC-D5, 4XC-D6, 4CX-D5, and 4CX-D6 groups. The differences in clinical pregnancy rate, live birth rate, first trimester abortion rate, preterm birth rate, gestational age, birth weight, and sex ratio at birth among the groups were compared.

Results

Our study showed that there was no difference in pregnancy and perinatal outcomes between the delayed formation of D6 high-quality expanded blastocysts and D5 expanded blastocysts, whether they were high-quality blastocysts or not. For low-quality blastocysts, the clinical pregnancy rate of D5 was higher than that of D6, and D5 was also better than D6 in live birth rate for those with inner cell mass rating B or above, while there was no difference between D5 and D6 for those with inner cell mass rating C.

Conclusion

Based on our research, we suggest that when we are developing the implantation strategy, we give priority to the selection of high-quality expanded blastocysts, regardless of D5 and D6, whose clinical outcomes are not different. For low-quality blastocysts, D5 expanded blastocysts are preferred for transfer.

Novel Time-Lapse Parameters Correlate with Embryo Ploidy and Suggest an Improvement in Non-Invasive Embryo Selection

Selecting the best embryo for transfer is key to success in assisted reproduction. The use of algorithms or artificial intelligence can already predict blastulation or implantation with good results. However, ploidy predictions still rely on invasive techniques. Embryologists are still essential, and improving their evaluation tools can enhance clinical outcomes. This study analyzed 374 blastocysts from preimplantation genetic testing cycles. Embryos were cultured in time-lapse incubators and tested for aneuploidies; images were then studied for morphokinetic parameters. We present a new parameter, "st₂, start of t₂", detected at the beginning of the first cell cleavage, as strongly implicated in ploidy status. We describe specific cytoplasmic movement patterns associated with ploidy status. Aneuploid embryos also present slower developmental rates (t₃, t₅, t_SB, t_B, cc3, and t₅-t₂). Our analysis demonstrates a positive correlation among them for euploid embryos, while aneuploids present non-sequential behaviors. A logistic regression study confirmed the implications of the described parameters, showing a ROC value of 0.69 for ploidy prediction (95% confidence interval (CI), 0.62 to 0.76). Our results show that optimizing the relevant indicators to select the most suitable blastocyst, such as by including st₂, could reduce the time until the pregnancy of a euploid baby while avoiding invasive and expensive methods.

Pregnancy Outcomes for Day 5 Versus Day 6 Single Frozen-thawed Blastocyst Transfer with Different Qualities of Embryos: A Large Matched-cohort Study

OBJECTIVE

This study aimed to determine whether the day of blastocyst expansion affects pregnancy outcomes in frozen-thawed blastocyst transfer (FBT) cycles.

METHODS

A retrospective match-cohort study was conducted. Patients who underwent blastocyst transfer in frozen-thawed cycles at day 5 or 6 were matched for potential confounding factors. A total of 2207 matched pairs of FBT cycles were included from January 2016 to December 2019 in our Reproductive Medicine Center.

RESULTS

The clinical pregnancy rate (CPR) and live birth rate (LBR) were significantly increased in day 5 blastocyst transfers when compared to day 6 blastocyst transfers, in terms of the same embryo quality. For FBT cycles with good-quality embryo, the CPR at day 5 and 6 was 61.30% and 57.56%, respectively (P=0.045), and the LBR was 44.79% and 36.16%, respectively (P<0.001). For FBT cycles with poor-quality embryo, the CPR at day 5 and 6 was 48.61% and 40.89%, respectively (P=0.006), and the LBR was 31.71% and 25.74%, respectively (P=0.019). The CPR for FBT cycles with good-quality embryo was statistically higher at day 6 than that at day 5 with poor-quality embryo transferred (57.56% vs. 48.61%, P=0.001). Maternal age, anti-Müllerian hormone (AMH), endometrial thickness, embryo quality, and the day of blastocyst expansion were independently correlated with the CPR and LBR. The FBT cycles at day 5 had significantly higher CPR (adjusted odds ratio [OR]=1.246, 95% confidence intervals [CI]: 1.097-1.415, P=0.001) and LBR (adjusted OR=1.435, 95% CI: 1.258-1.637, P<0.001) than those at day 6.

CONCLUSION

The embryo quality is the primary indicator for FBT cycles. Day 5 blastocysts should be preferred when the quality of embryo at day 5 is the same as that at day 6.

The pregnancy outcomes of day-5 poor-quality and day-6 high-quality blastocysts in single blastocyst transfer cycles

OBJECTIVE

This study compared the outcomes of single blastocyst transfer cycles, using day- 5 poor-quality blastocysts and day-6 high-quality blastocysts.

METHODS

We analyzed 462 frozen-thawed embryo transfer (FET) cycles performed at our center from January 2014 to December 2019. The cycles were divided into two groups: a day-5 poor-quality blastocyst transfer group (group A) and a day-6 high-quality blastocyst transfer group (group B). The clinical outcomes were tested.

RESULTS

In groups A and B, respectively, the clinical pregnancy rate (CPR; 61.65% vs. 67.17%, p=0.258), implantation rate (IR; 61.65% vs. 67.17%, p=0.258), and live birth rate (LBR; 69.51% vs. 77.83%, p=0.134) showed no significant differences. Moreover, when day-3 embryo quality was considered, the CPR, IR, and LBR were also similar in group A and group B (p>0.05).

CONCLUSION

The clinical outcomes of day-5 poor-quality blastocysts and day-6 high-quality blastocysts were similar, suggesting that the developmental speed of the embryo might be more important than embryo quality for the clinical outcomes of single blastocyst transfer in FET cycles.

Comparison of aneuploidy rate in spontaneous abortion chorionic villus between D6 and D5 thawed-frozen blastocyst transfer

BACKGROUND

To compare the aneuploidy rate in spontaneous abortion chorionic villus (SA-CV) after D5 and D6 thawed-frozen blastocyst transfer(TBT).

METHODS

This retrospective cohort study recruited 522 patients with early spontaneous abortion from March 2012 to January 2020 in the our center. The aneuploidy rate of SA-CV was compared according to the blastocyst development stage: D5 group (n = 398) and D6 group (n = 124).

RESULTS

Patients' characteristics, including age, body mass index, follicle-stimulating hormone, fertilization methods, type of infertility, infertility duration, and gestational age when abortion, did not differ between the two groups (all P > 0.05). Although the mean number of embryos was significantly higher in D6 than in the D5 group (P < 0.001), the mean number of high-quality embryos was similar (P = 0.773). In the D5 group, 46.5% of SA-CV showed aneuploidy, which was comparable to 41.1% in the D6 group (P = 0.296). After further grouping according to age (> 35 years or ≤ 35 years), the difference between the D5 and D6 groups remained not statistically significant (P = 0.247 and P = 0.690). Multivariate logistic analysis showed that women's age was independently associated with the aneuploidy rate (OR = 0.891; 95% CI: [0.854-0.930]; P < 0.001). The rate of chromosomal aneuploidy was significantly higher in the age > 35 years group than in the age ≤ 35 years group (61.0% vs. 39.4%, P < 0.001). Other factors, including blastocyst formation speed, were not significant predictors of aneuploidy rate.

CONCLUSIONS

The rate of chromosomal aneuploidy in SB-CV after D6 TBT was comparable to that after D5 TBT. Chromosomal aneuploidy may not be a main factor contributing to the high prevalence early pregnancy loss at D6 group.

Comparison of clinical outcomes for different morphological scores of D5 and D6 blastocysts in the frozen-thawed cycle

BACKGROUND

Both embryo development speed and embryo morphology score played a significant role in frozen-thawed embryo transfer cycle (FET) outcomes. Most of the literature indicates that D5 embryos performed better than D6 embryos, although a few also indicate that there is no difference in clinical outcomes between D5 and D6 embryos. Clinically, D5 embryos are preferred for equal morphological scores. But how to choose embryos when the morphological score of D6 embryos is better than D5?

METHODS

A retrospective study including 8199 frozen-thawed embryo transfers (FETs) was conducted to analyze patients who underwent IVF-FET from January 2018 to December 2020. Patients were divided into 8 groups according to the rate of embryonic development and morphological scores to compare pregnancy outcomes. We further compared clinical pregnancy outcomes and neonatal outcomes between BC embryos on day 5 (D5) and BA/BB embryos on day 6 (D6).

RESULTS

Our study found no difference in clinical pregnancy rate (CPR) and live birth rate (LBR) between AA/AB blastocysts in D5 or D6 frozen blastocysts. However, for BA/BB/BC blastocysts, embryonic pregnancy outcome was significantly better in D5 than in D6. In our further analysis and comparison of BC embryos in D5 and BA/BB embryos in D6, we found no difference in clinical pregnancy outcomes and neonatal outcomes, but D6 BA/BB embryos had a higher rate of miscarriage. After adjusting for confounding factors, none of the indicators differed between groups.

CONCLUSION

Our study provides suggestions for embryo selection: AA/AB embryos are preferred, regardless of the embryo development day, and the second choice is BA or BB embryos on D5. BA/BB embryos in D6 had a higher miscarriage rate than BC embryos in D5 but were not statistically significant after adjusting for confounding factors.

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.

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

Background

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

Methods

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

Results

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

Conclusions

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

Comparison of clinical outcomes of frozen-thawed D5 and D6 blastocysts undergoing preimplantation genetic testing

Background

This study aimed to analyze the clinical outcomes of blastocyst which undergo the preimplantation genetic testing (PGT) transplantation from frozen-thawed D5 and D6. In addition, the effect of blastocyst grade on clinical and neonatal outcomes was also investigated in this study.

Methods

The pregnancy and miscarriage rates of 1130 cycles of frozen embryo transfer, including 784 D5 frozen embryos and 346 D6 frozen embryos in the Reproductive Hospital of Shandong University from January to December 2020 were analyzed. Gardner blastocyst scoring was used for blastocyst evaluation.

Results

The pregnancy rate of D5 blastocyst was significantly higher, whereas the miscarriage rate of D5 blastocyst was lower, than that of D6 blastocyst tissue biopsy. No significant difference was observed in birth weight and low birth weight of D5 blastocyst and D6 blastocyst, preterm birth, gestational age, and neonatal sex. Frozen-thawed D5 blastocysts have higher pregnancy success rates and lower miscarriage rates compared to D6 blastocysts.

Conclusion

Therefore, both blastocyst grade and embryo biopsy date must be considered when transferring frozen embryos.

The influence of morphologic grading and COS protocol on the outcomes of Day 5 versus Day 6 single fresh blastocyst transfers: a retrospective analysis of clinical outcomes from one center experience

INTRODUCTION

The purpose of this study was to evaluate whether the blastocyst morphologic grading and the protocol of controlled ovarian stimulation (COS) would influence pregnancy outcomes, aiming to provide guidance when choosing blastocyst transfer.

METHODS

The clinical data of 612 patients who received single fresh blastocyst transfer for first cycle, as well as the data of 253 patients who had already delivered were analyzed retrospectively. The patients were divided into two groups according to blastocyst formation time (D5 or D6). The following subgroup analyses were performed: (i) the morphologic grading of blastocyst and (ii) the protocol of COS.

RESULTS

We observed that D5 single embryo transfer (SET) were associated with higher clinical pregnancy rate (CPR, 59.04% vs. 31.73%, P < 0.001) and live birth rate (LBR, 43.90% vs. 24.04%, P < 0.001) than D6 SET following fresh cycle. Patients in D5 group experienced more good blastocysts transfer (45.47%vs. 13.46%, P < 0.001) and less poor blastocysts transfer (9.64%vs. 45.19%, P < 0.001) than patients in D6 group. As to early stage and good quality blastocysts, the CPR and LBR were similar between D5 and D6 group. GnRH antagonist protocol had a demonstrable inferiority comparing with the early-follicular-phase long-acting GnRH-agonist long protocol (EFLL) or the mid-luteal-phase long-acting GnRH-agonist long protocol (MLLL) with regard to the CPR and LBR in D6-SET group.

CONCLUSIONS

The analysis found that ovarian reserve of patients in D6-SET group was comparatively worse than that of patients in D5-SET group and D6-SET patients represented a subgroup of infertility patients usually having relatively poor embryo quality. The results should be interpreted with caution as the very low numbers in the respective group limited the use of statistical tests and the real significance values.

Frozen blastocysts: Assessing the importance of day 5/day 6 blastocysts or blastocyst quality

The aim of the present study was to analyze the high-quality blastocyst (HB) rate in all embryo frozen cycles and investigate the pregnancy outcomes for day 5/day 6 (D5/D6) blastocysts with respect to the blastocyst quality in programmed single vitrified-warmed blastocyst transfer (SVBT). We performed a retrospective study comparing D5/D6 HBs in in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) for all blastocyst frozen cycles. Patients were <35 years at the oocyte collection in their first fresh cycle without fresh transfer. A total of 1,560 IVF/ICSI cycles and 5,328 blastocysts were analyzed. The IVF HB rate was higher than that of ICSI (52.7% vs. 42.6%; P<0.05). The D5 HB rate was much higher than the D6 HB rate (61.6% vs. 29.4%; P<0.05). There were 22.4% (349/1,560) cycles that only had D6 blastocysts, of which IVF cycles were lower than ICSI (19.8% vs. 28.5%; P<0.05). The clinical pregnancy rate and implantation rate in the D5 group were significantly higher than these rates in the D6 group (57.4% vs. 46.2%, 58.9% vs. 47.3%; P<0.05). However, the clinical pregnancy rate and implantation rate of the D5 HBs were not significantly different from those of the D6 HBs (60% vs. 54.5%, 62% vs. 56.3%; P>0.05). In conclusion, the fertilization method (IVF/ICSI) directly influences the HB rate and blastocyst development rates. When we controlled for patient age, transfer frequency, and endometrium on day 5, it was not the development stage (D5/D6), rather the transfer blastocyst quality that played an important role in pregnancy outcomes.

Birthweight After Frozen Embryos Formed on the Fifth Day Versus the Sixth Day: A Retrospective Analysis Including 17,127 Singleton Newborns

BACKGROUND

Transferring blastocysts frozen on day 6 (D6) may adversely affect the pregnancy rate compared with day 5 (D5). Moreover, it remains unclear whether delayed embryo transfer affects neonatal birth weight.

METHODS

A retrospective cohort study consisting of 17,127 singleton births from single frozen embryo transfer (FET) cycles, between January 2011 and January 2020, was performed including 14,166 blastocysts frozen on D5 and 2,961 on D6. The primary outcomes of this study were neonatal birth weight and incidence of small for gestational age (SGA), large for gestational age (LGA), low birth weight (LBW), and macrosomia.

RESULTS

The mean neonatal birth weight in the D5 group (3.47 ± 0.49 kg) was significantly higher compared with the D6 group (3.45 ± 0.50 kg), although the discrepancy was only 0.02 kg. Multiple linear regression analysis for birth weight between the two groups showed no statistically significant difference (β= -0.01 t= -1.218; P>0.05). Logistic regression analysis revealed that the risks of SGA (OR 1.166; 95%CI, 0.911-1.491; P>0.05), LGA (OR 0.917; 95%CI, 0.831-1.012; P>0.05), LBW (OR 1.192; 95%CI, 0.926-1.533; P>0.05), and macrosomia (OR 0.975; 95%CI, 0.864-1.100; P>0.05) were similar in the two groups after adjusting for confounders.

CONCLUSIONS

In the FET cycle, the neonatal birth weight and incidence of LGA, SGA, LBW, or macrosomia were similar between the D5 and D6 groups, suggesting that delayed blastocyst transfer would not affect the neonatal birth weight.

Correlation study of male semen parameters and embryo aneuploidy in preimplantation genetic testing for aneuploidy

OBJECTIVE

The purpose of this study was to evaluate the influence of abnormal semen parameters on embryo aneuploidy based on single nucleotide polymorphism microarray (SNP array).

METHODS

A total of 464 blastocysts from 103 PGT-A cycles were analyzed. The embryo quality and embryo aneuploidy rates were compared between different groups which divided by male semen parameters (sperm concentration, motility, morphology, and DFI) according the WHO criteria (2021).

RESULTS

The total blastocysts chromosome aneuploidy rate was 42.3% (191/452). In the teratozoospermia group, the good-quality embryo and blastocyst formation rate were lower than the normal group(44.4% vs 60.7%, P <0.01; 33.3% vs 43.5%, P <0.05), The good-quality embryo rate in normal DFI group was significantly higher than high-DFI group (59.0% vs 48.4%, P < 0.05). The blastocyst aneuploidy rate in low sperm concentration group, and high DFI group was no differences between with that in normal sperm concentration and DFI group (47.7% vs 37.8% and 44.7% vs 37.8%, P>0.05). The aneuploid rate of blastocyst in teratozoospermic and asthenozoospermia group was significantly higher than that of normal morphology and motility group (50.0% vs 34.0% and 46.7% vs 33.7%, P<0.05).

CONCLUSION

Our study revealed that sperm DFI were positively correlated with blastocyst aneuploidy rate, while sperm motility and sperm morphology rate were negatively correlated with blastocyst aneuploidy rate. Abnormal semen parameters may affect embryo quality and increase the aneuploidy rate of blastocyst chromosomes, suggesting that in clinical practice of assisted reproduction patients with abnormal semen parameters can be treated in advance to improve sperm quality, so as to reduce the impact on embryo quality and achieve a better pregnancy outcome.

Development and frozen-thawed transfer of non-pronuclear zygotes-derived embryos in IVF cycles

OBJECTIVE

To explore the development and pregnancy potential of non-pronuclear (0PN) zygote-derived embryos in conventional in vitro fertilization (IVF) cycles.

STUDY DESIGN

Embryonic development in 1039 oocyte retrieval cycles and clinical outcomes of 659 frozen-thawed blastocyst transfer cycles were retrospectively studied.

RESULTS

Developmental potential of embryos with different blastomere numbers on day 3 were inconsistent in 0PN and 2PN groups. For 0PN-derived embryos, blastocyst rate of fast developing embryos (75.4%) was similar to that of intermediately developing embryos (72.9%), but good quality blastocyst rate of the former (49.2%) was significantly higher than that of the later (39.6%). In 2PN group, intermediately developing embryos had the highest blastocyst rate (77.9%) and good quality blastocyst rate (51.5%) (statistically significant). Comparison of frozen-thawed transfer was carried out between 0PN- and 2PN-derived blastocysts. For both single (SBT) and double blastocyst transfer (DBT) groups, no statistical differences existed between 0PN- and 2PN-derived blastocysts in clinical pregnancy rates (45.2% and 49.1% in SBT group, 64.7% and 66.4% in DBT group), implantation rates (45.2% and 49.1% in SBT group, 41.2% and 47.7% in DBT group) and live birth rates (35.5% and 36.8% in SBT group, 52.9% and 51.2% in DBT group).

CONCLUSION

The developmental characteristic of 0PN-derived embryos was different from that of 2PN-derived embryos in IVF cycles. 0PN-derived blastocysts could obtain acceptable clinical pregnancy and live birth, but more studies are needed to confirm the safety..

Day 5 vitrified blastocyst transfer versus day 6 vitrified blastocyst transfer in oocyte donation program

The superiority of day 5 blastocysts compared to day 6 blastocysts in fresh cycle transfers was previously demonstrated and attributed mainly to endometrial asynchrony. Data from frozen blastocysts transfers showed conflicting results, possibly due to heterogeneous patient population and embryo quality. The aim of this study was to compare clinical pregnancy rate (CPR) and live birth rate (LBR) between transfers of vitrified day 5 blastocysts and day 6 blastocysts in oocyte donation, blastocyst-only cycles. In a retrospective, multi-center study, with a single oocyte donation program, a total of 1840 frozen embryo transfers (FET’s) were analyzed, including 1180 day 5 blastocysts and 660 day 6 blastocysts transfers. Day 5 blastocyst transfers had better embryonic development and significantly higher CPRs (34.24% vs. 20.15%, P < 0.0001), higher LBRs (26.89% vs. 14.77%, P < 0.0001), less cycles to LBR (1.83 ± 0.08 vs. 2.39 ± 0.18, P = 0.003) and shorter time to LBRs (76.32 ± 8.7 vs. 123.24 ± 19.1 days, P = 0.01), compared to day 6 transfers, respectively. A multivariate stepwise logistic regression indicated, that day 5 transfer was an independent factor for CPRs (OR 1.91; 95% CI 1.43–2.54, P < 0.001) and LBRs (OR 2.26; 95% CI 1.19–4.28, P = 0.01), regardless of embryo quality, compared to day 6. In conclusion, day 5 blastocysts in oocyte donation program have significantly higher CPRs and LBRs, and present shorter time to delivery, compared to day 6 blastocysts, regardless of embryo quality.

Effect of blastocyst morphology and developmental speed on transfer strategy for grade "C" blastocyst in vitrified-warmed cycles

BACKGROUND

High-quality single blastocyst transfer (SBT) is increasingly recommended to patients because of its acceptable pregnancy outcomes and significantly reduced multiple pregnancy rate compared to double blastocyst transfer (DBT). However, there is no consensus on whether this transfer strategy is also suitable for poor-quality blastocysts. Moreover, the effect of the development speed of poor-quality blastocysts on pregnancy outcomes has been controversial. Therefore, this study aimed to explore the effects of blastocyst development speed and morphology on pregnancy and neonatal outcomes during the frozen embryo transfer (FET) cycle of poor-quality blastocysts and to ultimately provide references for clinical transfer strategies.

METHODS

A total of 2,038 FET cycles of poor-quality blastocysts from patients 40 years old or less were included from January 2014 to December 2019 and divided based on the blastocyst development speed and number of embryos transferred: the D5-SBT (n = 476), D5-DBT (n = 365), D6-SBT (n = 730), and D6-DBT (n = 467) groups. The SBT group was further divided based on embryo morphology: D5-AC/BC (n = 407), D5-CA/CB (n = 69), D6-AC/BC (n = 580), and D6-CA /CB (n = 150).

RESULTS

When blastocysts reach the same development speed, the live birth and multiple pregnancy rates of DBT were significantly higher than those of SBT. Moreover, there was no statistical difference in the rates of early miscarriage and live birth between the AC/BC and CA/CB groups. When patients in the SBT group were stratified by blastocyst development speed, the rates of clinical pregnancy (42.44 % vs. 20.82 %) and live birth (32.35 % vs. 14.25 %) of D5-SBT group were significantly higher than those of D6-SBT group. Furthermore, for blastocysts in the same morphology group (AC/BC or CA/CA group), the rates of clinical pregnancy and live birth in the D5 group were also significantly higher than those of D6 group.

CONCLUSIONS

For poor-quality D5 blastocysts, SBT can be recommended to patients because of acceptable pregnancy outcomes and significantly reduced multiple pregnancy rate compared with DBT. For poor-quality D6, the DBT strategy is recommended to patients to improve pregnancy outcomes. When blastocysts reach the same development speed, the transfer strategy of selecting blastocyst with inner cell mass "C" or blastocyst with trophectoderm "C" does not affect the pregnancy and neonatal outcomes.

Which factors affect the likelihood of miscarriage after single euploid blastocyst transfer?

RESEARCH QUESTION

Which parameters affect the likelihood of miscarriage after single euploid frozen-thawed blastocyst transfer (FBT)?

DESIGN

In this retrospective study, clinical and laboratory data from 1051 single euploid FBTs were evaluated. Exclusion criteria were endocrine or systemic pathologies, uterine anomalies or pathologies, unilateral or bilateral hydrosalpinx, karyotypic abnormalities (either maternal or paternal) or thrombophilia. Patients were divided into two groups according to pregnancy outcome: live birth and miscarriage.

RESULTS

Body mass index (BMI) (25.98 ± 0.5 versus 24.36 ± 0.21, P = 0.019), duration of infertility (6.62 ± 0.54 versus 4.92 ± 0.18, P = 0.006) and number of previous miscarriages (1.36 ± 0.13 versus 0.79 ± 0.05, P < 0.001) were significantly higher in the miscarriage group (n = 100) than in the live birth group (n = 589). Although the trophectoderm and inner cell mass (ICM) percentage scores were not statistically different among the miscarriage and live birth groups, the percentage of day-6 biopsied embryos was significantly higher in the miscarriage group. Binary logistic regression analysis revealed that BMI (OR 1.083, 95% CI 1.013 to 1.158, P = 0.02) and number of previous miscarriages (OR 1.279, 95% CI 1.013 to 1.158, P = 0.038) were independent factors for miscarriage. Patients with elevated BMI and a higher number of miscarriages were at increased risk of miscarriage.

CONCLUSION

After a single euploid FBT, BMI and number of previous miscarriages are predictors of miscarriage. Lifestyle interventions before FBT may decrease miscarriage rates.

Should we look for a low-grade threshold for blastocyst transfer? A scoping review

Embryo quality is a key determinant of the success of IVF. Although the focus has been on selecting the best embryo for transfer, the classification of low-grade blastocysts (LGB) in existing scoring systems has received less attention. This is worrisome; embryo freezing allows optimal use of all created embryos, thus maximizing the cumulative live birth rate, which is arguably the most important outcome for infertile couples. A PubMed search was conducted in August 2020, using '((('poor-quality' OR 'poor quality') OR ('low-grade' OR 'low grade')) AND ('embryo' OR 'blastocyst')) AND ('pregnancy' OR 'live birth')'. This scoping review shows that LGB have similar euploidy and pregnancy success rates after implantation and have no adverse effects on pregnancy or perinatal outcomes. Evidence for pregnancy outcomes is lacking for different grades of LGB, with most studies clustering all LQB as one to compare with optimal blastocysts.

Live Birth Rate of Frozen-Thawed Single Blastocyst Transfer After 6 or 7 Days of Progesterone Administration in Hormone Replacement Therapy Cycles: A Propensity Score-Matched Cohort Study

BACKGROUND

Progesterone administration before transfer in hormone replacement treatment (HRT) is crucial to pregnancy outcomes in frozen-thawed blastocyst transfer (FET), but the optimal progesterone duration is inconsistent. The objective of this study was to investigate live birth rate (LBR) of different progesterone duration before blastocyst transfer in HRT-FET cycles.

METHOD

In this retrospective cohort study, patients underwent first HRT-FET (including suppression HRT) from January 2016 to December 2019 were included. Logit-transformed propensity score matching (PSM) was performed to assess covariates. The primary outcome was live birth rate after 28 weeks' gestation. Basing on different duration of progesterone before transfer, patients were classified into P6-protocol (blastocyst transfer performed on the sixth day), or P7-protocol (blastocyst transfer performed on the seventh day). Subgroup analyses were conducted as follows: age stratification (-35, 35-38, 38-), development days of blastocyst (D5 or D6), blastocyst quality (high-quality or poor-quality), and endometrial preparation protocols (HRT or suppression HRT).

RESULT

After case matching with propensity score methods, a total of 1,400 patients were included finally: 700 with P6-protocol and 700 with P7-protocol. Significantly higher live birth rate (38.43% versus 31.57%, respectively, P = 0.01) and clinical pregnant rate (50.43% versus 44.14%, respectively, P = 0.02) were observed in P6-protocol than those of P7-protocol. First-trimester abortion rates (18.13% versus 20.71%, P = 0.40) and ectopic pregnancy rates (2.27% versus 1.94%, P = 0.77) were similar between P6- and P7-groups. Preterm birth rate, low birth weight rate, newborn sex proportion, neonatal malformation rate were comparable between groups. Significantly higher LBRs were observed in patients with: age under 35, D5 blastocyst transfer, high-quality blastocyst transfer, and undergoing HRT cycles combined P6-protocol.

CONCLUSION

Frozen-thawed blastocyst transfer on the sixth day of progesterone administration in first HRT cycle is related to higher live birth rate compared with transfer on the seventh day, especially among patients aged under 35, D5 blastocyst and/or high-quality blastocyst transfer.

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.

Association between blastocyst morphology and live birth rate following frozen-thawed single blastocyst transfer: Results from a 5-year retrospective analysis of 2593 cryopreserved blastocysts

AIM

Our aim was to investigate associations between blastocyst morphology parameters and live birth outcome and to make possible additional recommendations for existing embryo selection strategies.

METHODS

This retrospective cohort study included 2593 frozen-thawed single blastocyst transfers (SBT) cycles from 2012 to 2016. Multivariable logistic regression model was used to analyze the independent predictive effectiveness of blastocyst parameters for live birth rate (LBR).

RESULTS

The participants enrolled in the present study were 32 (28-35) years old with a median body mass index of 21.20 (19.60-23.40) kg/m² , among whom 1058 (40.8%) women had live births. Among the three blastocyst morphology parameters, we found only inner cell mass grade and trophectoderm cell grade had significant effects on LBR (P < 0.001). When adjusting for potential confounders in a multivariable logistic regression model, the expansion and hatching (EH) stage of blastocoel also showed obvious correlation with LBR. Blastocysts at EH stage 4-5 had a significantly higher LBR than that at stage 3 (P < 0.05). Additionally, the timing of blastulation was also an important predictor of LBR. Blastocysts vitrified on day 6 and day 7 yielded a lower LBR than that vitrified on day 5 (P < 0.001).

CONCLUSION

The timing of blastulation and all blastocyst morphology parameters were associated with LBR independently. Although the most important parameter for predicting clinical outcomes remains undetermined, the timing of blastulation was a stable predictor of live birth for frozen-thawed SBT.

D6 blastocyst transfer on day 6 in frozen-thawed cycles should be avoided: a retrospective cohort study

Background

There is no definitive evidence about the suitable timing to transfer blastocysts formed and cryopreserved on day 6 (D6 blastocysts) in frozen-thawed embryo transfer (FET) cycles. This study aimed to investigate the suitable timing to transfer D6 blastocysts in FET cycles and to identify factors affecting clinical pregnancy rate (CPR) and early miscarriage rate (EMR) in FET cycles with blastocysts.

Methods

This retrospective cohort study included 1788 FET cycles with blastocysts. There were 518 cycles with D6 blastocysts, and 1270 cycles with blastocysts formed and cryopreserved on day 5 (D5 blastocysts) (D5 group). According to the blastocyst transfer timing, the cycles with D6 blastocysts were divided into cycles with D6 blastocysts transferred on day 5 (D6-on-D5 group, 103 cycles) and cycles with D6 blastocysts transferred on day 6 (D6-on-D6 group, 415 cycles). The chi-square test, independent t-test or Mann-Whitney test, and logistic regression analysis were used for data analysis.

Results

The CPR and implantation rate (IR) were significantly higher in the D6-on-D5 group than in the D6-on-D6 group (55.3% vs. 37.3%, 44.8% vs. 32.6%, P < 0.01). The CPR and IR were significantly higher in the D5 group than in the D6-on-D5 group (66.0% vs. 55.3%, 62.1% vs. 44.8%, P < 0.05), and the EMR was significantly lower in the D5 group than in the D6-on-D5 group (11.2% vs. 21.1%, P < 0.05). Logistic regression analysis demonstrated that transfer D6 blastocysts on day 5, instead of day 6, could significantly increase the CPR (odds ratio[OR]: 2.031, 95% confidence interval (CI): 1.296–3.182, P = 0.002). FET cycles with D6 blastocysts transferred on day 5 had a higher EMR than those with D5 blastocysts (OR: 2.165, 95% CI: 1.040–4.506, P = 0.039). Hormone replacement therapy (HRT) cycles exhibited a higher EMR than natural cycles (OR: 1.953, 95% CI: 1.254–3.043, P = 0.003), while no difference was observed in the CPR (P > 0.05).

Conclusions

These results indicate that the suitable timing to transfer D6 blastocysts in FET cycles may be day 5, and D6 blastocyst transfer on day 6 in FET cycles should be avoided. D6 blastocysts transfer and HRT cycles may be associated with a higher EMR.

Effects of euploid blastocyst morphological development on reproductive outcomes

Blastocyst culture and transplantation have now been widely used in most reproductive centers. Our aim was to explore the effects of euploid blastocyst morphological development on the reproductive outcomes of frozen-thawed euploid blastocysts on the fifth day or sixth day. The retrospective analysis included the clinical data of 849 patients who underwent euploid blastocyst transplantation between January 2014 and January 2018. The patients were divided into well-developed blastocysts (BB) or poorly developed blastocysts (BC, CB) groups according to blastocyst morphology grade. The intracytoplasmic sperm injection (ICSI) was carried out on the day of egg retrieval. Morphological evaluation of the resulting blastocysts was performed on Day5 or Day6 of in vitro culture. The pregnancy rate, cumulative pregnancy rate, live birth rate and cumulative live birth rate were the highest in the BB group (P ≤ 0.001). In addition, not only the pregnancy rate of CB group Day5 was lower than that of the BB (P = 0.005) and BC (P = 0.042) groups, but the live birth rate in CB group was lower than BB (P = 0.001) and BC (P = 0.007) groups. However, there was no difference in miscarriage rate among the three groups (P = 0.154). Furthermore, the miscarriage rate of BB (P = 0.048) and BC (P = 0.019) groups at the Day5 cycle was lower than the Day6 cycle. Blastocyst morphological development has positive effects on pregnancy rate and live birth rate, but has no effect on miscarriage rate.

Frozen-warmed blastocyst transfer after 6 or 7 days of progesterone administration: impact on live birth rate in hormone replacement therapy cycles

OBJECTIVE

To study the difference in live birth rate (LBR) between frozen-warmed blastocyst transfer (FET) on the 6th or the 7th day of progesterone administration in artificially prepared cycles.

DESIGN

Retrospective cohort study.

SETTING

Tertiary university-based referral hospital.

PATIENT(S)

Patients who underwent FET between December 2015 and December 2017 in a hormone replacement therapy cycle (HRT).

INTERVENTION(S)

Group A included all eligible patients who underwent transfer of a vitrified-warmed blastocyst on the 6th day of progesterone administration; group B included patients who underwent blastocyst transfer on the 7th day of progesterone. The artificial HRT protocol in this study consisted of estrogen administration at a dose of 2 mg twice daily for 7 days followed by 2 mg three times daily for 6 days and micronized vaginal progesterone 200 mg three times daily from an adequately considered endometrial thickness onward.

MAIN OUTCOME MEASURE(S)

Live birth rate.

RESULTS

The study included 619 patients, 346 in group A and 273 in group B. The LBRs were comparable between both groups (36.6% for group A and group B), even after adjustment for confounding factors (adjusted odds ratio 1.073, 95% confidence interval 0.740-1.556). Subgroup analysis revealed significantly higher miscarriage rates for day 6 blastocysts transferred on the 6th day of progesterone supplementation compared with transfer on the 7th day of progesterone supplementation (50.0% versus 21.4%, respectively). Additionally, there was a tendency toward a higher LBR when the 7-day progesterone supplementation protocol was used for transfer of a day 6 blastocyst (21.5% and 35.5% for group A and group B, respectively).

CONCLUSION

Warmed blastocyst transfer on the 6th compared with the 7th day of progesterone administration in an HRT cycle results in similar LBR. Subgroup analysis of day 6 blastocysts showed significantly higher miscarriage rates when FET was performed on the 6th day of progesterone administration.

Choosing the optimal blastocyst by morphology score versus developmental rate in frozen-thawed embryo transfer cycles

The aim of this study was to provide guidance for better management in the selection of blastocyst to warm in frozen-thawed embryo transfer (FET) cycles. A retrospective cohort follow-up study was conducted that included single autologous frozen blastocyst transfer cycles performed in our Reproductive Medicine Unit from January 2009 to December 2016. The live birth rate (LBR), clinical pregnancy rate (cPR) were increased as blastocyst morphology scores increased, but the miscarriage rate decreased in all groups. In the high-score groups, there were no differences in LBR between D5 and D6, while in the low-score groups, LBR was significantly higher in D5 compared to the D6. With respect to neonatal outcome, there were no differences in all the groups. After binary logistic regression analysis, it was seen that patients' age, thawed cycles, pre-frozen morphology score and developmental rate were independently associated with LBR. These results suggest that for high-scoring blastocyst, the pre-frozen morphological score should be given priority while for low-scoring blastocysts, the developmental rate should be given priority when thawing in FET cycles.

The Influence of Delayed Blastocyst Development on the Outcome of Frozen-Thawed Transfer of Euploid and Untested Embryos

Objective

The primary objective is to compare live birth rates (LBRs) following frozen embryo transfer (FET) of euploid day 5 with day 6 blastocysts. We also compared LBRs following FET of untested blastocysts vitrified on day 5 and day 6 in self-oocyte and ovum donation (OD) cycles.

Design

This was a retrospective observational study.

Setting

Nova IVF Fertility, Ahmedabad.

Materials and Methods

Ninety-seven FET using self-oocytes following preimplantation genetic testing A (PGT-A), 464 FET following OD, and 907 FET using self-oocytes without PGT-A testing between January 2016 and December 2017 were included in this study.

Main Outcome Measures

LBR following FET in day 5 versus day 6 blastocysts in euploid embryos using self-oocytes and in untested embryos using both self and donor oocytes.

Results

In PGT-A cycles, no statistically significant difference was observed in LBRs following transfer of euploid blastocysts developed on day 5 or day 6 (D5: 53%; D6:40%, P = 0.83). However, the LBRs with day 5 blastocysts were higher compared with day 6 group in untested group using both self and donor oocytes (self D5: 52.7%; D6: 38.2%; P = 0.001 and OD D5: 44.7%; D6: 29.8%; P = 0.001). Miscarriage rates were comparable in both the groups.

Conclusions

The present study demonstrated comparable pregnancy outcomes following FET of euploid embryos vitrified on day 5 and day 6. However, higher LBRs were reported in day 5 group in untested embryos.

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.

Parameters impacting the live birth rate per transfer after frozen single euploid blastocyst transfer

Background

To assess the predictive value of patient characteristics, controlled ovarian stimulation and embryological parameters on the live birth outcome of single euploid frozen-warmed blastocyst transfer (FBT).

Methods

This was a retrospective cohort study including 707 single FBTs after preimplantation genetic testing for aneuploidy (PGT-A) that were performed from October 1, 2015, to January 1, 2018. The effects of patient-, cycle- and embryology-related parameters on the live birth outcome after FBT were assessed.

Results

In the subgroup analysis based on live birth, patients who achieved a live birth had a significantly lower body mass index (BMI) than patients who did not achieve a live birth (22.7 (21.5–24.6) kg/m² vs 27 (24–29.2) kg/m², p<0.001). The percentage of blastocysts with inner cell mass (ICM) A or B was significantly higher among patients achieving a live birth, at 91.6% vs. 82.6% (p<0.001). Day-5 biopsies were also more prevalent among patients achieving a live birth, at 82.9% vs 68.1% (p<0.001). On the other hand, the mitochondrial DNA (mtDNA) levels were significantly lower among cases with a successful live birth, at 18.7 (15.45–23.68) vs 20.55 (16.43–25.22) (p = 0.001). The logistic regression analysis showed that BMI (p<0.001, OR: 0.789, 95% CI [0.734–0.848]), day of trophectoderm (TE) biopsy (p<0.001, OR: 0.336, 95% CI [0.189–0.598]) and number of previous miscarriages (p = 0.004, OR: 0.733, 95% CI [0.594–0.906]) were significantly correlated with live birth. Patients with elevated BMIs, cycles in which embryos were biopsied on day-6 and a higher number of miscarriages were at increased risks of reduced live birth rates.

Conclusion

A high BMI, an embryo biopsy on day-6 and a high number of miscarriages negatively affect the live birth rate after single euploid FBT.

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.

Increased pregnancy outcome after day 5 versus day 6 transfers of human vitrified-warmed blastocysts

Vitrification is a highly efficient technique for the cryopreservation of the human embryo. The effect of delayed blastulation may be responsible for implantation failures and negatively affects in vitro fertilization (IVF) outcomes. The current literature displays discordant results; some studies have announced higher pregnancy rates after day 5 (D5) transfer compared with day 6 (D6) transfer, while others have shown equivalent outcomes. In the present study an investigation into the clinical implications of delayed blastulation (D5 versus D6) was carried out. We performed a retrospective study comparing clinical pregnancies and implantation rates following warmed single blastocyst transfer (WSBT). All patients coming for a programmed warmed transfer at Edinburgh Assisted Conception Programme, EFREC, Royal Infirmary of Edinburgh, were included in this study and divided in two groups according to the day of blastocyst vitrification: D5 (n = 1563) and D6 (n = 517). The overall survival rate was 95.0% (1976/2080) with no significant difference between the D5 and D6 groups: 95.3% (1489/1563) and 94.2% (487/517) respectively. WSBT of D6 blastocysts resulted in a lower implantation and clinical pregnancy compared with D5 embryos. The implantation rate (IPR) and clinical pregnancy rate (CPR) were respectively 49.4% and 42.6% for the D5 and 37.4% and 32.2% for the D6 embryos, which was statistically significant. The multiple pregnancy rate was 1.32% (1.14% for D5 vs 1.84% for D6). Although the transfer of D6 vitrified-warmed blastocyst remains a reasonable option, priority to a D5 embryo would reduce the time to successful pregnancy.

Increased live births after day 5 versus day 6 transfers of vitrified-warmed blastocysts

PURPOSE

An investigation into the clinical implications of delayed blastulation (day 5 versus day 6) was carried out for cryo cycles, as heterogeneous results persist in the current literature.

METHODS

We performed a retrospective study comparing clinical pregnancies and live births between 178 blastocysts vitrified and warmed on day 5 versus 149 on day 6. The stage of blastocyst development was taken into account and adjustment for confounding factors was performed.

RESULTS

Our results demonstrate a significant difference in clinical pregnancy (43 versus 23% p value < 0.001) and live birth rates (34 versus 16% p value < 0.001) regarding the day of vitrification, in favour of day 5. This difference persisted after adjustment for confounding factors. The adjusted odds ratio for clinical pregnancies and deliveries for the day 5 group compared to that of the day 6 group was 2.83 (95%CI, 1.48 to 5.41) and 2.94 (95%CI, 1.39 to 6.22), respectively. When the stage of development of the blastocyst was taken into consideration, we still observed a significant advantage of day 5 versus day 6 vitrification.

CONCLUSIONS

Day of vitrification (day 5 versus day 6) appears to be an independent predictor of clinical outcomes. Stratification of our cohort was carried out according to the developmental stage, and significant differences persisted. Although the transfer of day 6 cryopreserved embryos remains a viable option, giving priority to a day 5 embryo would reduce the time to pregnancy.

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.