The safety of long-term cryopreservation on slow-frozen early cleavage human embryos

Long-term storage does not affect the DNA methylation profiles of vitrified-warmed human embryos

With the widespread application of embryo cryopreservation in assisted reproductive techniques, it is necessary to assess the safety of long-term cryopreservation of human embryos and it is unclear whether storage time has an impact on the DNA methylation profiles of human embryos. Nine women who received IVF treatment were recruited for this study. The retrieved eight-cell human embryos were classified into three groups including fresh embryos, cryopreserved embryos stored for 3 years, and cryopreserved embryos stored for 8 years. Single-cell whole-genome bisulfite sequencing (scWGBS) was conducted. The genome-wide methylation pattern of the fresh and two cryopreserved groups were similar. In addition, the methylation level in different genomic regions showed comparable patterns and no significant differences were observed in the methylation level of imprinted genes among the three groups. A total of 587 differentially methylated regions (DMRs) in the 3-year group and 540 DMRs in the 8-year group were identified comparing to fresh group. However, they were not enriched in promoters and had a similar genome-wide distributions, suggesting that these DMRs may not contribute to the changes in corresponding gene expressions. Our study illustrated that long-term cryopreservation will not affect the DNA methylation profiles of human eight-cell embryos at single-cell level.

Storage time does not influence pregnancy and neonatal outcomes for first single vitrified high-quality blastocyst transfer cycle

RESEARCH QUESTION

Does blastocyst storage time have an impact on pregnancy and neonatal outcomes following the first single vitrified/warmed high-quality blastocyst transfer cycle for young women?

DESIGN

Retrospective cohort study in a university-affiliated reproductive medical centre.

RESULTS

A total of 2938 patients undergoing their first frozen embryo transfer (FET) cycle with a single high-quality blastocyst (Day 5: 3BB and above; Day 6: 4BB and above) transferred were divided into five groups: Group A with storage time ≤3 months (n = 1621), Group B with storage time of 4-6 months (n = 657), Group C with storage time of 7-12 months (n = 225), Group D with storage time of 13-24 months (n = 104), and Group E with storage time of 25-98 months (n = 331). After adjusting for confounding factors by multivariate logistic regression, there were no significant differences in live birth rate [Group A as reference; Group B: adjusted odds ratio (aOR) 0.954 (95% CI 0.791- 1.151); Group C: aOR 0.905 (95% CI 0.674-1.214); Group D: aOR 0.727 (95% CI 0.474-1.114); Group E: aOR 1.185 (955 CI 0.873-1.608)], β-human-chorionic-gonadotropin-positive rate, clinical pregnancy rate and miscarriage rate between Group A and the other groups. Among all singletons born after FET, there were no significant differences with regards to gestational age, preterm birth, birthweight, low birthweight, high birthweight and macrosomia.

CONCLUSION

Long-term cryostorage of human vitrified high-quality blastocysts does not affect pregnancy or neonatal outcomes.

Delivery of a Healthy Child Through International Gestational Surrogacy 10 Years Following Female Fertility Preservation and In Vitro Fertilization (IVF) for Recurrent Breast Cancer: A Case Report

Assisted reproduction technology (ART) has made considerable progress in recent years; in particular with regard to cryopreservation, long-term storage, successful thawing, and embryo transfer of cryopreserved embryos. Regarding gestational surrogacy, progress has been made in the areas of awareness, social acceptance, regulation, legislation, availability, streamlining, and optimization of cross-border care. The above is being highlighted in the current presentation of a particularly challenging and novel case. A 43-year-old woman visited our clinic in Greece, seeking international gestational surrogacy due to recurrent breast cancer which rendered her medically unfit for pregnancy. Ten years before her initial visit to our clinic the patient had undergone fertility preservation due to breast cancer, her oocytes had been fertilized with her husband's sperm, and the embryos were cryopreserved and stored in a fertility clinic based in the United Kingdom. The stored embryos were transported to Greece, thawed, and successfully implanted to the selected gestational surrogate. Following an uneventful pregnancy, the surrogate delivered a healthy girl. This successful outcome exemplified innovation, motivation, and hope and may represent a paradigm of team scientific excellence associated with positive patient outcomes. Furthermore, this case constitutes the successful culmination of major advances made in various different sectors of cross-border reproductive care; laboratory, clinical, legal, ethical, and logistical.

Storage duration of vitrified embryos does not affect pregnancy and neonatal outcomes after frozen-thawed embryo transfer

Background

With the refinement of cryopreservation technology, the number of frozen-warmed embryo transfer (FET) cycles and cryopreserved embryos has increased rapidly. However, studies investigating the effect of storage duration on pregnancy outcomes after vitrification are limited and their results are controversial. Furthermore, the available studies did not take patients' demographic nor clinical treatment characteristics into account and the cryo-storage duration was short. So this study aimed to explore the effect of storage duration of vitrified warmed embryos on pregnancy and neonatal outcomes in patients with good prognosis and long storage duration of vitrified embryos.

Methods

This study was a bi-centre, retrospective study including 1037 women undergoing their first FET cycles following a fresh cycle from January 2012 until December 2021. Patients were divided into four storage groups in accordance with the storage duration of transferred embryos (612 patients in group I, with storage duration between 1 and 6 months; 202 patients in group II, with storage duration between 7 and 12 months; 141 patients in group III, with storage duration between 13 and 36 months; and 76 patients in group IV, with storage duration between 37 and 84 months). The pregnancy and neonatal outcomes were compared amongst different storage duration groups.

Results

Amongst the different groups, no significant differences were observed in the pregnancy outcomes, including biochemical pregnancy rate, implantation rate, clinical pregnancy rate, ongoing pregnancy rate and live birth rate. In addition, no evidence of differences amongst different storage duration groups was observed in terms of preterm birth, birth length and low birthweight.

Conclusions

The pregnancy and neonatal outcomes of embryos after vitrification were not impaired by storage duration up to 7 years.

Effects of vitrified cryopreservation duration on IVF and neonatal outcomes

Background

In this study, we aimed to evaluate the impact of the duration of cryopreservation storage on embryo viability, implantation competence, pregnancy outcome and neonatal outcomes.

Methods

We retrospectively evaluated the outcomes of patients who underwent IVF with vitrified cryopreserved embryos between January 2004 and August 2019 by following the first frozen embryo transfer cycles within the study period. A total of 31,143 patients met the inclusion criteria and were grouped according to the embryo storage time as follows: Group 1 (n = 20,926),1–90 days; Group 2 (n = 6,472), 91–180 days; Group 3 (n = 2,237), 181–365 days; Group 4 (n = 746), 366–730 days; and Group 5 (n = 762), > 731 days.

Results

The embryo survival rate decreased significantly with longer durations of cryopreservation. The highest and lowest survival rate was recorded in Group 1 and Group 5, respectively (34853/35338; 98.63% vs. 1281/1801; 71.13%; P < 0.01). The human chorionic gonadotropin (HCG) detection and clinical pregnancy rate was highest in Group 1 (57.85% and 55. 26%, respectively; P < 0.01). Short-term cryopreservation (≤ 3 months) is associated with higher rates of clinical pregnancy. There were no significant differences in neonatal birth weight, neonatal height and congenital anomalies among the groups (P > 0. 05).

Conclusion

The prolonged storage time of vitrified embryos negatively affected survival rate and clinical pregnancy rate. It did not have a significant influence on neonatal health. This study provides new findings about the relationship between prolonged storage time of vitrified embryos and clinical outcomes and offers evidence for the safety of using long-stored embryos after vitrification.

Long-term cryopreservation and frozen embryo transfer do not impact clinical and neonatal outcomes: a retrospective cohort study of slow-frozen early-cleavage human embryos

This study aimed to evaluate the effect of the cryopreservation duration (up to 160 months) on the clinical and neonatal outcomes of slow-frozen early-cleavage human embryos. Clinical data collected between February 2013 and August 2017 were included in this retrospective study. Cases were classified into five groups by the duration of cryopreservation: Group 1, 6-12 months; Group 2, 13-36 months; Group 3, 37-60 months; Group 4, 61-84 months; and Group 5, >84 months. The embryo survival rate, implantation rate, clinical pregnancy rate, live-birth rate, newborn sex ratio, singleton gestational age, singleton birth weight and malformation rate were compared between the groups. The cryopreservation duration did not significantly affect the rates of clinical pregnancy (P = 0.119) and live birth (P = 0.354), the newborn sex ratio (P = 0.614) or the singleton gestational age (P = 0.212) and birthweight (P = 0.212). Although decreases in the embryo survival and implantation rates were observed in groups 4 and 5 compared with those in groups 1-3, these differences were not statistically significant (P = 0.329, P = 0.279, respectively). Long-term cryopreservation does not appear to adversely affect the clinical and neonatal outcomes of slow-frozen early-cleavage human embryos.

Long-Term Storage Does Not Affect the Expression Profiles of mRNA and Long Non-Coding RNA in Vitrified-Warmed Human Embryos

Although vitrification has been widely applied in assisted reproductive technology, it is unknown whether storage time has any impact on the mRNA and lncRNA expression profiles in human embryos. Eleven women (aged 23-35 years) who had undergone in vitro fertilization treatment were recruited for this study. The transcriptomes of 3 fresh eight-cell embryos and 8 surviving vitrified-warmed eight-cell embryos (4 embryos were cryostored for 3 years, and the others were cryostored for 8 years) were analyzed through single-cell RNA-Seq. No differentially expressed mRNAs or lncRNAs were identified between the 3-years group and 8-years group. A total of 128 mRNAs and 365 lncRNAs were differentially expressed in the 8 vitrified-warmed embryos compared with the fresh embryos. The vitrification-warming impact was moderate, and it was mainly related to the pathways of metabolism, stress response, apoptosis, cell cycle, cell adhesion, and signaling for TFG-β and Hippo. The analysis of target mRNAs suggested that lncRNAs might contribute to the regulation of mRNAs after vitrification-warming. Our findings indicated that long-term storage after vitrification does not affect the mRNA and lncRNA expression profiles in human embryos, however, the procedure of vitrification-warming would lead to minor alteration of transcriptome.

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

RESEARCH QUESTION

The study aimed to retrospectively evaluate the impact of cryo-storage duration on clinical, obstetric and perinatal outcomes after vitrified-warmed euploid blastocyst transfer.

DESIGN

This was an observational study including 2688 vitrified-warmed euploid single blastocyst transfers that was conducted at a private IVF centre between May 2013 and March 2020. It included a total of 1884 women (age 38 ± 3 years) undergoing at least one transfer after preimplantation genetic testing for aneuploidies. The euploid blastocysts transferred were clustered into seven groups according to the cryo-storage duration between vitrification and warming: ≤60 days (n = 646; control group), 61-90 days (n = 599), 91-180 days (n = 679), 181-360 days (n = 405), 361-720 days (n = 144), 721-1080 days (n = 118) and >1080 days (n = 97). The primary outcome was the live birth rate (LBR) per transfer. The secondary outcomes were miscarriage rate, obstetric and perinatal issues. The data were adjusted for confounders through logistic or linear regressions.

RESULTS

A significantly lower LBR was reported for transfers performed within 91-180 days (n = 291/679, 42.9%; P = 0.017), 181-360 days (n = 169/405, 41.7%; P = 0.016) and 361-720 days (n = 57/144, 39.6%; P = 0.034) versus ≤60 days (n = 319/646, 49.4%). However, this was mainly due to top-quality embryos being transferred first when more euploid blastocysts were available, thereby leaving lower quality ones for subsequent procedures. Indeed, the multivariate odds ratios adjusted for confounders showed similar results across all cryo-storage duration clusters. No difference was reported also for all secondary outcomes.

CONCLUSIONS

Cryo-storage duration even beyond 3 years from blastocyst vitrification does not affect clinical, obstetric and perinatal outcomes.

The effect of storage time after vitrification on pregnancy and neonatal outcomes among 24 698 patients following the first embryo transfer cycles

STUDY QUESTION

To evaluate the impact of storage time after vitrification on embryo viability, pregnancy outcomes and neonatal outcomes.

SUMMARY ANSWER

The prolonged storage time of vitrified embryos negatively affected pregnancy outcomes, including biochemical pregnancy rate, clinical pregnancy and live birth rate; but did not influence neonatal outcomes.

WHAT IS KNOWN ALREADY

Although vitrification has been the fundamental tool of ART treatments in recent years, few studies have explored the influence of storage period after vitrification on embryonic and clinical outcomes.

STUDY DESIGN, SIZE, DURATION

A retrospective study was performed among 24 698 patients with the first vitrified embryo transfer following a freeze-all strategy during the period from January 2011 to December 2017.

PARTICIPANTS/MATERIAL, SETTING, METHODS

A total of 24 698 patients met the inclusion criteria and were grouped according to the storage time (11 330 patients in Group 1 with storage time <3 months, 9614 patients in Group 2 with storage time between 3 and 6 months, 3188 patients in Group 3 with storage time between 6 and 12 months and 566 in Group 4 with storage time between 12 and 24 months). The pregnancy outcomes and neonatal outcomes were compared between different storage time groups. Multivariate logistic regression and linear regression were performed to evaluate the independent effect of storage time on clinical outcomes, adjusting for important confounders.

MAIN RESULTS AND THE ROLE OF CHANCE

After adjustment for potential confounding factors, the chance of biochemical pregnancy (Group 1 as reference; Group 2: adjusted odds ratio (aOR) = 0.92, 95% CI 0.87-0.97; Group 3: aOR = 0.83, 95% CI 0.76-0.90; Group 4: aOR = 0.68, 95% CI 0.56-0.81), clinical pregnancy (Group 2: aOR = 0.91, 95% CI 0.86-0.96; Group 3: aOR = 0.80, 95% CI 0.73-0.87; Group 4: aOR = 0.65, 95% CI 0.54-0.79) and live birth (Group 2: aOR = 0.89, 95% CI 0.85-0.95; Group 3: aOR = 0.83, 95% CI 0.76-0.91; Group 4: aOR = 0.59, 95% CI 0.48-0.72) significantly decreased with the increasing storage time, whereas the relationship between miscarriage, ectopic pregnancy and storage time did not reach statistical significance. In addition, there was no evidence of differences in adverse neonatal outcomes (preterm birth, low birthweight, high birthweight, macrosomia or birth defects) between groups.

LIMITATION, REASONS FOR CAUTION

Our study was limited by the retrospective design from a single center, the conclusion from our study needs to be verified in further studies.

WIDER IMPLICATIONS OF THE FINDINGS

This study provides new findings about the relationship between prolonged storage time of vitrified embryos and clinical outcomes and offers evidence for the safety of using long-stored embryos after vitrification.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the National Natural Science Foundation of China (grant nos. 81903324, 81771533, 81571397, 81701523), National Key Research and Development Program of China (grant no. SQ2018YFC100163). None of the authors have any conflicts of interest to declare.

Storage Time of Cryopreserved Embryos and Pregnancy Outcomes: A Dose-Response Meta-Analysis

Purpose Cryopreservation techniques have become an essential part of assisted reproduction technology. Embryos may be cryopreserved for several years before transfer, and the safety of long-term cryopreservation needs to be considered. This dose-response meta-analysis was conducted to evaluate whether there were dose-response relationships between the storage time of cryopreserved embryos and pregnancy outcomes such as survival rate, implantation rate, miscarriage rate, clinical pregnancy rate, and congenital malformation rate. Methods After searching the databases PubMed, Embase, MEDLINE, CCRT and related reviews up until June 4, 2020, seven studies were included for analysis. Two reviewers extracted the relevant information and independently assessed the study quality using the Newcastle-Ottawa scale. Potential linear or non-linear dose-response relationships were assessed with a random-effect dose-response meta-analysis. Results No dose-response association was found between duration of embryo cryostorage and survival rate, implantation rate, miscarriage rate, clinical pregnancy rate or congenital malformation rate. Conclusion The interval between the start of embryo cryopreservation and frozen/thawed embryo transfer does not influence pregnancy outcomes.

The Impact of Embryo Storage Time on Pregnancy and Perinatal Outcomes and the Time Limit of Vitrification: A Retrospective Cohort Study

BACKGROUND

The technique of embryo cryopreservation has been increasingly applied in clinical settings. However, there has been a concern about the safety and efficacy of long-term freezing of embryos. Therefore, the aim of this study was to evaluate whether storage time of vitrification had any effects on pregnancy as well as perinatal outcomes, further, to explore the appropriate time limit of vitrification.

METHODS

The study included women who underwent at least one frozen-thawed cycle with single embryo transfer between January 1^st, 2016 and September 30^th, 2019. Patients were assigned into 3 groups according to the storage time (<3 months, 3-12 months and >12 months) to evaluate the impact of embryo storage time on pregnancy and perinatal outcomes. To further investigate the time limit of vitrification, propensity score matching was used to compare the primary outcomes of patients with storage time of 1-3 years, 3-5 years, and >5 years to those stored for ≤1 year.

RESULTS

A total of 9806 frozen-thawed embryo transfer cycles were included in our study. After adjustment for confounding variables, no significant differences were found in pregnancy outcomes among groups. However, postponement of transfer increased the risks of large for gestational age and placenta previa. In addition, after propensity score matching, 171 cycles with storage time >5 years were matched with those ≤1 year, both the clinical pregnancy rate and live birth rate decreased significantly when the storage time exceeded 5 years.

CONCLUSIONS

The duration of vitrification did not significantly affect the pregnancy outcomes within 5 years period. However, the clinical pregnancy rate and live birth rate both decreased significantly when the duration of vitrification exceeded 5 years. It is worth noting that the conclusion was drawn from a small sample study after propensity score matching and should be treated with caution. In addition, the cycles were from different time periods, which could have an impact on the results.

Influence of storage time on vitrified human cleavage-stage embryos froze in open system

BACKGROUND

During in vitro fertilization, rapid growth of vitrification and liquid nitrogen storage of embryos have been well characterized. However, the effect of storage time on vitrified cleavage-stage embryos in an open system is poorly understood.

AIMS

To investigate the influence of storage time on the survival and pregnancy outcomes of vitrified human cleavage-stage embryos froze and stored in an open system.

METHODS

A retrospective study of 786 vitrified-warmed cycles of 735 patients was performed from January 2013 to October 2013. The cycles were divided into five groups according to storage time: 1-3 months, 4-6 months, 7-12 months, 13-24 and 25-60 months. The clinical outcomes of cycles with different storage time were analyzed.

RESULTS

There were no significant differences of the survival rate, clinical pregnancy outcomes, birth rate, gestational weeks and singleton birthweights at various storage times.

CONCLUSION

For vitrified embryos froze and stored in an open system, the storage time would not influence the survival rate and pregnancy outcomes by storage time up to 5 years.

The clinical outcomes of day 3 4-cell embryos after extended in vitro culture

OBJECTIVE

To evaluate the development potential and clinical significance of day 3 4-cell embryos after extended in vitro culture.

METHODS

This study was a retrospective cohort study for patients with infertility treatment between January 2011 and July 2013. Patients undergoing blastocyst culture in controlled ovarian hyperstimulation cycles using surplus embryos were analyzed in the study. A total of 764 women undergoing blastocyst culture with 1,522 surplus 4-cell embryos on day 3 were analyzed. An additional 2,391 patients with embryos undergoing blastocyst culture during the same period with embryos having more blastomeres were chosen as control.

RESULTS

After extended culture, 253 embryos from 183 cycles in the study group which developed to blastocysts were frozen, and 118 embryos were warmed in subsequent frozen embryo transfer cycles. Implantation rates, clinical pregnancy rates (PRs) and ongoing PRs were 33.3 %, 38.4 % and 31.4 %, respectively, which were similar to those of the control group. The singleton birth weights of newborns using these blastocysts showed no significant difference to that seen in the control group.

CONCLUSION

Surplus 4-cell embryos on day 3 displayed lower blastulation rates. However, once a blastocyst is obtained, it has equivalent clinical outcomes. Embryos that are developmentally lagging on day 3 can be observed in extended culture to increase the cumulative chances of a successful pregnancy.