Outcomes of day 3 embryo transfer with vitrification using Cryoleaf: a 3-year follow-up study

Objective

To compare success rates of vitrified-warmed with fresh and frozen-thawed ETs

Design

Retrospective.

Setting

Public fertility center.

Patient(s)

Cryopreserved- thawed/warmed ETs were included in this study. Fresh cycles, in which supernumerary embryos were cryopreserved, were set as the fresh control group.

Intervention(s)

Supernumerary day 3 embryos were cryopreserved by slow-freezing or vitrification and transferred after thawing or warming.

Main Outcome Measure(s)

Comparison of two cryopreservation techniques with respect to post-thaw survival of embryos, implantation and pregnancy rates, neonatal outcome, and congenital birth defects.

Results

A total of 962 fresh, 151 freezing-thawed and 300 vitrified-warmed cycles were included in this study. The survival and intact cell rates in the vitrification group were significantly higher compared with those in the slow freezing group (88.5?% vs 74.5?% and 86.6?% vs 64.0?%). The implantation, clinical pregnancy and live birth rates of the vitrification group were similar to the fresh and significant higher than slow freezing group. There were no significant differences in mean gestational age, birth weight, stillbirth, birth defects and the prevalence of neonatal diseases among three groups.

Conclusion

Vitrified-warmed ETs yield comparable outcomes with fresh ETs and is superior to frozen-thawed ETs regarding the survival rate and clinical outcomes.     

Vitrification of blastocysts derived from fair to poor quality cleavage stage embryos can produce high pregnancy rates after warming

Purpose

This study investigates whether certain embryos considered unsuitable for cryopreservation on day 3 might nevertheless have the potential to develop into worthwhile blastocysts that could be vitrified in the same cycle.

Methods

Retrospective study: between 2010 and 2011, embryo transfers and cryopreservation took place mainly on day 3 in our centre. Supernumerary embryos of intermediate to poor quality were reassessed on days 5/6 and any good quality blastocysts were vitrified.

Results

Out of 914 cleavage stage (day 3) embryos left in culture, 16 % were vitrified on days 5/6. Fifty blastocyst warming cycles resulted in a 76 % survival rate, 44 % clinical pregnancy rate and 39 % implantation rate. During the same time period, 213 warming cycles of good quality cleavage stage embryos rendered survival rates, clinical pregnancy and implantation rates of 97 %, 23 % and 16 % respectively.

Conclusions

Supernumerary average quality day 3 embryos should be given a second chance to be selected for cryopreservation. If blastocysts are obtained and survive vitrification, there is a good chance of implantation thus reducing embryo waste.     

The freezing method of cleavage stage embryos has no impact on the weight of the newborns

Purpose

The aim of this study was to study the effect of the embryo freezing method on the birth weight of newborns from frozen embryo transfer (FET) cycles, and the pregnancy results of cleavage stage embryos cryopreserved by slow freezing or vitrification.

Methods

This is a retrospective cohort study undertaken in a University Hospital IVF unit using concurrently both the slow-freezing and the vitrification techniques. All frozen-thawed and vitrified-warmed day 2 and day 3 embryo transfers during the time period from 1 April 2009 to 31 November 2013 were included in the study.

Results

There was no statistically significant weight difference between newborns from vitrified or slow-frozen embryos (3588 vs 3670 g). A higher post-thaw viability rate was achieved after cryopreservation by the vitrification technique compared to the slow-freezing protocol (83.4 vs 61.4 %). The miscarriage rate was lower in the vitrification group (15.7 vs 29.0 %). The live birth rates were similar (19.5 vs 19.1 %) in the slow-freezing and vitrification groups, respectively. Among vitrified embryos, 7.4 embryos needed to be thawed to produce one delivery; in the slow-freezing group, that number was 11.9.

Conclusions

The freezing method has no impact on the weight of the newborn.With lower post-thaw survival rates and higher miscarriage rates, the slow-freezing cryopreservation protocol is inferior to the vitrification technique.

     

Comparison of the clinical outcomes between fresh blastocyst and vitrified-thawed blastocyst transfer

Objective

To compare the clinical outcomes between fresh and vitrified-thawed day 5 blastocyst transfers.

Design

Retrospective case control study.

Setting

Tertiary referral center.

Patient(s)

Patients 38 years of age or less who underwent IVF/ICSI cycles with fresh or frozen-thawed blastocysts transferred from June 1, 2009 to November 30, 2011

Intervention(s)

Vitrification and thawing of day 5 blastocysts using the Cryotop method. (Kitazato BioPharma Co., Ltd., Fuji city, Shizuoka, Japan)

Main outcome measure(s)

Clinical pregnancy rate, implantation rate, ongoing pregnancy rate, and multiple pregnancy rates.

Results

Of the 118 cycles in the fresh transfer group, 234 blastocysts were transferred. The clinical pregnancy rate was 66.1 % and implantation rate was 50.9 %. The ongoing pregnancy rate was 56.8 % and the rates for singleton and twin pregnancies were 53.7 % and 44.8 %. Of the 59 cycles in the vitrified-thawed group, 111 blastocysts were transferred. The clinical pregnancy rate was 59.3 % and implantation rate was 43.2 %. The ongoing pregnancy rate was 47.5 % and the rates for singleton and twin pregnancies were 60.7 % and 39.3 %. The clinical pregnancy rate, implantation rate and ongoing pregnancy rate did not differ significantly between the two groups.

Conclusions

The implantation rates were not significantly different between the fresh and the vitrified-thawed groups. Thus, single embryo transfer may be considered in fresh cycles to decrease multiple pregnancy rates. The surplus embryos should be vitrified for the frozen embryo transfer to improve the cumulative pregnancy rate.     

Large-volume vitrification of human biopsied and non-biopsied blastocysts: a simple,robust technique for cryopreservation

Purpose

To evaluate the transition from a proven slow-cooling cryopreservation method to a commercial large-volume vitrification system for human blastocysts.

Methods

Retrospective analysis of de-identified laboratory and clinical data from January 2012 to present date for all frozen embryo replacement (FET) cycles was undertaken. Cryopreservation of trophectoderm-biopsied or non-biopsied blastocysts utilized during this time period was logged as either slow-cooling, small-volume vitrification, or large-volume vitrification. Blastocyst survival post-warm or post-thaw, clinical pregnancy following FET, and implantation rates were identified for each respective cryopreservation method.

Results

Embryo survival was highest for large-volume vitrification compared to micro-volume vitrification and slow-cooling; 187/193 (96.9 %), 27/32 (84.4 %), and 244/272 (89.7 %), respectively. Survival of biopsied and non-biopsied blastocysts vitrified using the large-volume system was 105/109 (96.3 %) and 82/84 (97.6 %), respectively. Survival for micro-volume biopsied and non-biopsied blastocysts was 16/30 (83.3 %) and 2/2 (100.0 %) respectively. Slow-cooling post-thaw embryo survival was 272/244 (89.7 %). Clinical pregnancy and implantation rates outcomes for non-biopsied embryos were similar between large-volume and slow-cooling cryopreservation methods, 18/39 (46.2 %) clinical pregnancy and 24/82 (29.3 %) implantation/embryo, and 52/116 (44.8 %) clinical pregnancy and 67/244 (27.5 %) implantation/embryo, respectively. Comparing outcomes for biopsied embryos, clinical pregnancy and implantation rates were 39/67 (58.2 %) clinical pregnancy and 50/105 (47.6 %) implantation/embryo and 4/16 (25 %) clinical pregnancy and 6/25 (24.0 %) implantation/embryo, respectively.

Conclusions

The LifeGlobal large-volume vitrification system proved to be very reliable, simple to learn and implement in the laboratory. Clinically large-volume vitrification was as, or more effective compared to slow-cooling cryopreservation in terms of recovery of viable embryos in this laboratory.     

Live birth following serial vitrification of embryos and PGD for fragile X syndrome in a patient with the premutation and decreased ovarian reserve

Purpose

To present a live birth resulting from serial vitrification of embryos and pre-implantation genetic diagnosis (PGD).

Methods

A 31-year-old with primary infertility, fragile-X premutation, and decreased ovarian reserve (DOR) (baseline FSH level 33 IU/L), presented after failing to stimulate to follicle diameters >10 mm with three cycles of invitro fertilization (IVF). After counseling, the couple opted for serial in-vitro maturation (IVM), embryo vitrification, and genetic testing using array comparative genomic hybridization (aCGH) and PGD. Embryos were vitrified 2 days after intra-cytoplasmic sperm injection (ICSI). Thawed embryos were biopsied on day-three and transferred on day-five.

Results

The couple underwent 20 cycles of assisted reproductive technology. A total of 23 in-vivo mature and five immature oocytes were retrieved, of which one matured in-vitro. Of 24 embryos, 17/24 (71 %) developed to day two and 11/24 (46 %) survived to blastocyst stage with a biopsy result available. Four blastocysts had normal PGD and aCGH results. Both single embryo transfers resulted in a successful implantation, one a blighted ovum and the other in a live birth.

Conclusions

Young patients with DOR have potential for live birth as long as oocytes can be obtained and embryos created. Serial vitrification may be the mechanism of choice in these patients when PGD is needed.     

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.

     

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

Objective

To evaluate the impact of cryopreservation storage time on cleavage-stage embryo survival rate, pregnancy rate, implantation rate, singleton birth weight, and live birth rate.

Methods

This study was a retrospective analysis, including 867 thaw cycles and 3,367 embryos. Women who underwent IVF-FET cycles between 2005 and 2012 were analyzed. The patients were divided into four groups, as follows: group 1 (12–23 months); group 2 (24–35 months); group 3 (36–48 months); and group 4 (≥48 months).

Results

The storage time did not have a significant effect on survival, damage rate of the blastomeres, implantation rate, pregnancy rate, singleton birth weight, and live birth rate for embryos frozen at cleavage stages.

Conclusion

Storage time did not influence the survival and pregnancy outcomes of slow-frozen early cleavage human embryos. The developmental potential of cryopreserved human embryos with different storage times does not appear to have a negative influence on further development.     

Association of serum estradiol levels on the day of hCG administration with pregnancy rates and embryo scores in fresh ICSI/ET cycles down regulated with either GnRH agonists or GnRH antagonists

Purpose

To investigate the interrelation between serum E2 level on hCG day, score of transferred embryos and pregnancy achievement.

Methods

Records of 350 women aged 18–40 years who underwent ovarian hyperstimulation in fresh cycles down regulated either with GnRH agonist (n = 70) or GnRH antagonist (n = 280) followed by oocyte pick-up, ICSI and embryo transfer are retrospectively analyzed.

Results

Median E2 levels on hCG day of cycles ending with and without pregnancy were similar (p = 0.308). ROC curve for AUC of E2 on hCG day with dependent variable pregnancy rate also demonstrated that the E2 level on hCG day cannot be used to predict pregnancy in IVF/ICSI cycles (AUC 0.532, 95 % confidence interval: 0.471–0.593). Grouping cycles according to their E2 levels on hCG day also did not demonstrate any detrimental effect of either low or high E2 levels on hCG day both in agonist and antagonist cycles. Pregnancy rates are strongly correlated with mean and total score of transferred embryos. Interrelation of E2 on hCG day and pregnancy rate is independent from score of transferred embryos.

Conclusions

E2 on hCG day is not correlated with pregnancy rates and cannot be used to predict pregnancy in neither agonist nor antagonist cycles, no matter its level or percentile is used.     

Developmentally delayed cleavage-stage embryos maintain comparable implantation rates in frozen embryo transfers

Purpose

In fresh IVF cycles, embryos reaching the eight-cell stage on day 3 of development are thought to have a higher chance of implantation than those reaching this stage on day 4. To determine whether this difference persists after cryopreservation, we compared pregnancy and implantation rates between frozen embryo transfer (FET) cycles using delayed cleavage-stage embryos (cryopreserved day 4) and normal cleavage-stage embryos (cryopreserved day 3).

Methods

Participants underwent FET between 2008 and 2012 using embryos cryopreserved on either day 3 (n = 76) or day 4 (n = 48), depending on the length of time needed to achieve the eight-cell stage. All embryos, regardless of day of cryopreservation, were thawed and transferred on the 4th day of vaginal progesterone following endometrial preparation with oral estradiol. Chi-square and Mann-Whitney U tests were used to compare patient demographics and cycle outcomes.

Results

More women in the day 4 group had diminished ovarian reserve (44 vs 16 %, p = 0.003). Pregnancy outcomes in preceding fresh cycles were not different between the two groups. Pregnancy, implantation, and live birth rates following FET did not differ between the day 3 and day 4 groups.

Conclusions

This is the first study to address outcomes using day 3 versus day 4 cryopreserved embryos. Despite a higher prevalence of diminished ovarian reserve (DOR) in the day 4 group, delayed cleavage-stage embryos utilized in FET cycles performed as well as embryos growing at the normal rate, suggesting delayed embryo development does not affect embryo implantation as long as endometrial synchrony is maintained.     

The expression and distribution of aquaporin 3 in mouse embryos before and after vitrification

Purpose

To determine the role of aquaporin 3 (AQP3) isoform in early embryonic development and protecting embryos subjected to freeze–thawing for assisted reproduction, we investigated the expression and distribution of AQP3 in mouse embryos at different developmental stages before and after vitrification.

Methods

Eight-cell embryos, morulae, and blastocysts were obtained from female mice that had been superovulated by controlled ovarian hyperstimulation. Immunofluorescence staining, laser confocal microscopy, and Western blot were used to determine the expression and distribution of AQP3 in preimplantation mouse embryos before and after vitrification.

Results

AQP3 was expressed at the 8-cell to blastocyst stage before and after vitrification. The expression and distribution of AQP3 was developmentally regulated at the 8-cell to blastocyst stage. The expression of AQP3 was significantly decreased in 8-cell embryos and early blastocysts after vitrification. However, at the morulae stage, the expression of AQP3 was increased after vitrification.

Conclusions

The developmental and vitrification-dependent changes in AQP3 expression and distribution suggest that this transmembrane channel might regulate mouse embryo development and contribute to the protective response during vitrification.     

Effect of the site of assisted hatching on vitrified-warmed blastocyst transfer cycles: a prospective randomized study

Purpose

To assess the effect of assisted hatching (AH) site on the clinical outcomes in vitrified-warmed blastocyst transfer cycles.

Methods

A total of 160 women who underwent vitrified-warmed blastocyst transfer cycles were randomized to either the ICM group (AH performing at the site near the inner cell mess, ICM), or the TE group (AH performing at the site opposite to the ICM). AH with laser zona drilling was performed 20 or 30 min after thawing once the ICM can be detected. Clinical pregnancy rate, implantation rate, live birth rate and the occurrence rate of monozygotic twins (MZT) pregnancy after transfer of these two groups were compared.

Results

No significant difference was found in the clinical pregnancy rate (63.8 % vs. 67.5 %), implantation rate (51.7 % vs. 53.6 %) and live birth rate (57.5 % vs. 62.5 %) between the ICM group and the TE group. The occurrence rate of MZT was comparable between the two groups (3.9 % vs. 5.6 %).

Conclusions

The site of assisted hatching has no influence on the implantation, pregnancy and live birth rate in human vitrified-warmed blastocyst transfer cycles.     

Slow freezing should not be totally substituted by vitrification when applied to day 3 embryo cryopreservation: an analysis of 5613 frozen cycles

Purpose

This study aimed to compare slow freezing (SF) and vitrification (VT) techniques for day 3 embryo cryopreservation in infertile couples.

Methods

This retrospective cohort study enrolled 5613 infertile patients, with 7862 frozen-thawed day 3 embryos and 3845 vitrified-warmed day 3 embryos, from 2010 to 2014, at a single center. The rates of embryo survival, pregnancy, implantation, miscarriage, live birth, and live birth weight were compared between the two groups.

Results

A total of 5613 cycles with 5520 transfers were analyzed. Using SF, the rates of overall embryo survival and fully intact blastomeres were lower than those in VT (91.5 vs. 97.4 % and 68.7 vs. 92.3 %, respectively). The rate of good quality embryos after thawing/warming was lower in SF than in VT. In single frozen embryo transfer cycles (FETs), the pregnancy and implantation rates were similar between the two groups (35.0 vs. 40.8 % and 34.6 vs. 35.9 %, respectively). In double FETs, the pregnancy rate per cycle was also similar between the groups (58.8 vs. 58.4 %). The implantation rate per embryo transfer was significantly higher with SF than with VT (38.8 vs. 34.6 %). With adjustment for maternal age and the number of good quality embryos, differences in implantation rate remained significant (adjusted P value, SF vs. VT P < 0.05). No independent effect was found for the method of cryopreservation on the pregnancy rate. No significant differences in the rates of miscarriage, live birth, and live birth weight were observed between the two techniques.

Conclusions

Despite the significantly low embryo survival rate, fully intact blastomere rate, and good quality embryo rate in SF, the pregnancy and implantation rates were not adversely affected in single and double FETs. SF yielded an equivalent miscarriage rate, live birth rate, and live birth weight compared with VT. The SF protocol to cryopreserve day 3 embryos still should be considered.     

Does combined prednisolone and low molecular weight heparin have a role in unexplained implantation failure?

Purpose

To study the effect of combined oral prednisolone and LMW heparin in ICSI in women with previously unexplained, failed implantation.

Methods

A prospective quasi-randomized, controlled trial was conducted at a university teaching hospital and a private practice setting. A total of 334 cycles (women with previously unexplained, failed one or two ICSI attempts) were assigned randomly to receive standard treatment or combined prednisolone (20 mg/day), starting on the first day of ovarian stimulation and LMW heparin 1 mg/kg/day starting 1 day after oocyte retrieval in addition to standard treatment.

Results

The mean age, number of previously failed IVF attempts, and basal FSH levels were comparable between both groups. The pregnancy and the implantation rates were significantly different between the study and control groups.

Conclusions

A combination of oral prednisolone and low molecular weight heparin may have a significant effect on pregnancy and implantation rates in prior unexplained, failed implantation.     

Vitrification of human early cavitating and deflated expanded blastocysts: clinical outcome of 474 cycles

Purpose

The present study was undertaken to evaluate and compare the post thaw survival, implantation and pregnancy rates of vitrified human early cavitating blastocysts with deflated expanded blastocysts.

Material and methods

Supernumerary blastocysts were vitrified in 30% ethylene glycol-dimethyl sulphoxide based solution using cryoloop. Fully expanded blastocysts were deflated by gentle aspiration of the blastocoelic fluid using a micromanipulator until the cavity collapses prior to vitrification.

Results

Of the 576 vitrified blastocysts, 545 (94.61%) survived thawing in the early cavitating blastocyst group which was significantly higher than deflated expanded blastocyst group, in which only 370 survived thawing out of 459 (80.62%). However, no significant difference was observed in implantation and pregnancy rates between early cavitating and deflated expanded blastocyst groups.

Conclusions

Early cavitating blastocyst would be the ideal stage for cryopreservation of human blastocysts as it has higher survival rate and avoids additional invasive procedures like deflation of the blastocoele.     

Artificial shrinkage of blastocysts prior to vitrification improves pregnancy outcome: analysis of 1028 consecutive warming cycles

Purpose

This study aims to compare implantation, pregnancy, and delivery rates in frozen transfer cycles with blastocysts that were vitrified either with artificial shrinking (AS group) or without (NAS group).

Methods

Retrospective comparative study of artificial shrinking of blastocysts prior to vitrification and frozen embryo transfer cycles in infertile patients undergoing frozen embryo transfer (FET) was done at the Humanitas Fertility Center between October 2009 and December 2013. Main outcome measure(s) were implantation (IR), pregnancy (PR), and delivery rates (DR) between the two groups.

Results

A total of 1028 consecutive warming blastocyst transfer cycles were considered. In 580 cycles (total of 822 blastocysts), artificial shrinking was performed prior to vitrification (AS group), while in the remaining 448 cycles (total of 625 blastocysts), the artificial shrinking was not performed (NAS group). There were no differences in patient age (36.4?±?3.7 vs. 36.3?±?3.9) and number of embryos transferred (1.41?±?0.49 vs. 1.38?±?0.50) between groups. The IR, PR, and DR in the AS group were significantly higher (p?<?0.05) than in the NAS group (29.9 vs. 23.0 %, 36.3 vs. 27.9 %, and 26.5 vs. 18.1 %, respectively).

Conclusions

Performing AS of blastocysts prior to vitrification appears to improve implantation, pregnancy, and delivery rates probably related to a decreased risk of ultrastructural cryodamages, plausible when cryopreserving expanded blastocysts.

     

Combination of cabergoline and embryo cryopreservation after GnRH agonist triggering prevents OHSS in patients with extremely high estradiol levels—a retrospective study

Purpose

Embryo cryopreservation after triggering oocyte maturation with GnRH agonist (GnRHa) in GnRH antagonist protocols has been proposed to prevent ovarian hyperstimulation syndrome (OHSS). However, a small percentage of patients still developed severe OHSS. The purpose of the study was to investigate the efficacy of preventing OHSS in patients at very high risk when cabergoline was given in addition to elective cryopreservation after GnRHa triggering.

Methods

This is a retrospective observational study. The patients were stimulated with GnRH antagonist protocol. When serum E₂ concentration was >6,000 pg/ml and there were more than 20 follicles ≥11 mm on the day of final oocyte maturation, GnRHa was used to trigger oocyte maturation. Cabergoline was given to augment the effect of preventing OHSS. The embryos were electively cryopreserved by vitrification and thawed in subsequent cycles. The primary outcome measure was the incidence of severe OHSS. The secondary outcome measure was the clinical pregnancy rate in the first frozen-thawed embryo transfer cycle.

Results

One hundred and ten patients underwent 110 stimulated cycles were included for analysis. No patients developed moderate/severe OHSS. Mean E₂ concentration on the day of final oocyte maturation was 7,873 pg/ml, and an average of 22.7 oocytes was obtained from each patient. One hundred and ten thawing cycles were performed, resulting in 69 clinical pregnancies (62.7 %).

Conclusions

Combining cabergoline and embryo cryopreservation after GnRHa triggering in GnRH antagonist protocol could prevent OHSS in patients at very high risk.     

A randomized controlled trial comparing two vitrification methods versus slow-freezing for cryopreservation of human cleavage stage embryos

Purpose

To compare two different vitrification methods to slow freezing method for cryopreservation of human cleavage stage embryos. Design: Prospective randomised trial. Setting: University assisted reproduction centre. Patient(s): 568 patients (mean age 33.4 ± 5.2) from April 2009 to April 2011.

Methods

1798 supernumerary good-quality cleavage stage embryos in 645 IVF cycles intended to be cryopreserved were randomly allocated to three groups: slow freezing, vitrification with the Irvine® method, vitrification with the Vitrolife® method. Main Outcome Measure(s): Embryo survival and cleavage rates, implantation rate.

Results

A total of 1055 embryos were warmed, 836 (79.2 %) survived and 676 were finally transferred (64.1 %). Post-warming embryos survival rate was significantly higher after vitrification (Irvine: 89.4 %; Vitrolife: 87.6 %) than after slow freezing (63.8 %) (p < 0.001). No differences in survival rates were observed between the two vitrification methods, but a significant higher cleavage rate was observed using Irvine compared to Vitrolife method (p < 0.05). Implantation rate (IR) per embryo replaced and per embryo warmed were respectively 15.8 % (41/259) and 12.4 % (41/330) for Irvine, 17.0 % (40/235) and 12.1 % (40/330) for Vitrolife, 21.4 % (39/182) and 9.9 % (39/395) for slow-freezing (NS).

Conclusions

Both vitrification methods (Irvine and Vitrolife) are more efficient than slow freezing for cryopreservation of human cleavage stage embryos in terms of post-warming survival rate. No significant difference in the implantation rate was observed between the three cryopreservation methods.     

Closed vitrification of human oocytes and blastocysts: outcomes from a series of clinical cases

Purpose

High survival rates and clinical outcomes similar to those from fresh oocytes and blastocysts have been observed with open oocyte vitrification systems. It has been suggested that the extremely fast cooling rates that are only achieved with open systems are necessary for human oocyte and blastocyst vitrification. However, there is a potential risk of introducing contamination with open systems. The aim of this study was to assess whether similar survival and subsequent implantation rates could be achieved using a closed vitrification system for human oocytes and blastocysts.

Methods

Initially, donated immature oocytes that were matured in vitro were vitrified using the cryoprotectants ethylene glycol (EG) + dimethyl sulphoxide (DMSO) + sucrose and either a closed system (Rapid-i®) or an open system (Cryolock). The closed system was subsequently introduced clinically for mature oocyte cryopreservation cases and blastocyst vitrification.

Results

Using in vitro matured oocytes, a similar survival was achieved with the open system of 92.4 % (73/79) and with the closed system of 89.7 % (35/39). For clinical oocyte closed vitrification, high survival rate of 90.5 % (374/413) and an implantation rate of 32.7 % (18/55) from the transfer of day 2 embryos was achieved, which is similar to fresh day 2 embryo transfers. Blastocysts have also been successfully cryopreserved using the Rapid-i closed vitrification system with 94 % of blastocysts having an estimated ≥75 % of cells intact and a similar implantation rate (31.5 %) to fresh single blastocyst transfers.

Conclusion

Closed vitrification can achieve high survival and similar implantation rates to fresh for both oocytes and blastocysts.

     

Impact of the size of zona pellucida thinning area on vitrified-warmed cleavage-stage embryo transfers: a prospective, randomized study

Purpose

The aim of this study was to determine if the size of zona pellucida thinning area by laser assisted hatching could affect the rates of pregnancy and implantation for vitrified-warmed embryo transfers at the cleavage-stage.

Methods

A total of 120 vitrified-warmed cleavage-stage embryo transfers were randomly assigned to either quarter or half of zona pellucida thinning group.

Results

The rates of clinical pregnancy (46.7 versus 25.0%) and implantation (32.0 versus 16.2%) were significantly greater in the half thinning group than in the quarter thinning group (P?=?0.0218 and P?=?0.0090, respectively).

Conclusions

The results of this investigation show that, in vitrified-warmed embryo transfers at the cleavage-stage, the size of zona pellucida thinning area by laser assisted hatching impacts the rate of clinical pregnancy and implantation and that half of zona pellucida thinning significantly increases both of these results compared with quarter of zona pellucida thinning.