Laser-assisted removal of necrotic blastomeres from cryopreserved embryos that were partially damaged

Complementarity between Early Embryogenesis and Uterine Receptivity: Toward Integrative Approach to Female Infertility Management. Editorial to the Special Issue "Molecular Mechanisms of Human Oogenesis and Early Embryogenesis"

Two highly relevant papers were recently been published in the Special Issue of Molecular Sciences entitled "Molecular Mechanisms of Human Oogenesis and Early Embryogenesis" [...].

Cleavage-stage embryo micromanipulation in the clinical setting

Embryo micromanipulation was developed after introduction of microinjection to overcome infertility. Embryo micromanipulation may be performed at any embryo stage from pronuclear to blastocyst. The technique started out as basic and turned out to be increasingly more complex. Embryo micromanipulation at the cleavage-stage includes a wide range of techniques, from opening the zona pellucida in order to improve the chance of implantation, to removing detrimental components from the embryo to enhance embryo development or blastomeres for preimplantation genetic diagnosis and embryo splitting. Evaluating the impact(s) of different micromanipulation techniques on epigenetics of the embryo and considering quality control during these techniques are important issues in this regard. This review aims to discuss the micromanipulation of cleavage-stage embryos in clinical assisted reproductive technology (ART).

ABBREVIATIONS

ART: assisted reproductive technology; ICSI: intracytoplasmic sperm injection; IVF: in vitro fertilization; PGD: preimplantation genetic diagnosis; PZD: partial zona dissection; ZP: zona pellucida; SUZI: subzonal insemination; PVS: perivitelline space; AH: assisted hatching; LAH: laserassisted hatching; ZT: zona thinning; UV: ultraviolet; IR: infrared; PCR: polymerase chain reaction; FISH: fluorescent in situ hybridization; NGS: next generation sequencing; QC: quality control; QA: quality assurance.

Analysis of embryo intactness and developmental potential following slow freezing and vitrification

The aim of this study was to identify the parameters that are related to intactness and developmental potential of a day 3 embryo after warming to improve the selection criteria used to cryopreserve and transfer embryos. We also sought to compare slow freezing and vitrification methods of cryopreservation and to evaluate the viability of non-intact embryos. Embryos warmed following slow freezing (n=220) or vitrification (n=522) were divided into 3 groups according to the proportion of surviving blastomeres (I<50%; II=50-99%; and III=100%). The developmental potential of embryos, including the mitosis resumption rate, blastocyst formation rate, and formation rate of grade A blastocysts (i.e., fully expanded blastocysts with an inner cell mass and grade A or B trophectoderm) were retrospectively assessed in embryos. Cleavage-stage embryos with <50% blastomere survival were analyzed using next-generation sequencing (NGS). Logistic regression analysis showed that vitrification and grade 1 were independent predictive factors of embryo intactness and developmental potential (all p<0.05). On day 3, embryos with 4-6 cells or blastomere damage had lower developmental potential than those with 7-9 cells or intact blastomeres (all p<0.05). NGS results showed that the chromosomal status was completely normal in 8 embryos that developed into expanded blastocysts, whereas 4 out of 5 embryos in which development was arrested were abnormal. The results of this study suggest that vitrification is a better choice than slow freezing for embryo cryopreservation. Embryos showing poor quality (fragmentation >30% and/or a non-stage-specific cell size) and lower cell numbers (4-6 cells) on day 3 should be cultured to the blastocyst stage and then vitrified if they develop into good-quality blastocysts. The developmental potential of non-intact embryos is lower than that of intact embryos; however, after they are cultured to the fully expanded blastocyst stage, embryos with <50% blastomere survival appear to be better candidates for transfer. Abbreviations ART: assisted reproductive technology; grade A blastocyst: fully expanded blastocyst with an inner cell mass and grade A or B trophectoderm; NGS: next-generation sequencing; IVF: in vitro fertilization; ICSI: intracytoplasmic sperm injection; FET: frozen-thawed embryo transfer.

A critical appraisal of cryopreservation (slow cooling versus vitrification) of human oocytes and embryos

BACKGROUND

Vitrification is now a commonly applied technique for cryopreservation in assisted reproductive technology (ART) replacing, in many cases, conventional slow cooling methodology. This review examines evidence relevant to comparison of the two approaches applied to human oocytes and embryos at different developmental stages.

METHODS

Critical review of the published literature using PubMed with particular emphasis on studies which include data on survival and implantation rates, data from fresh control groups and evaluation of the two approaches in a single setting.

RESULTS

Slow cooling is associated with lower survival rates and compromised development relative to vitrification when applied to metaphase II (MII) oocytes, although the vitrification results have predominantly been obtained using direct contact with liquid nitrogen and there is some evidence that optimal protocols for slow cooling of MII oocytes are yet to be established. There are no prospective randomized controlled trials (RCTs) which support the use of either technique with pronuclear oocytes although vitrification has become the method of choice. Optimal slow cooling, using modifications of traditional methodology, and vitrification can result in high survival rates of early embryos, which implant at the same rate as equivalent fresh counterparts. Many studies report high survival and implantation rates following vitrification of blastocysts. Although slow cooling of blastocysts has been reported to be inferior in some studies, others comparing the two approaches in the same clinical setting have demonstrated comparable results. The variation in the extent of embryo selection applied in studies can lead to apparent differences in clinical efficiency, which may not be significant if expressed on a 'per oocyte used' basis.

CONCLUSIONS

Available evidence suggests that vitrification is the current method of choice when cryopreserving MII oocytes. Early cleavage stage embryos can be cryopreserved with equal success using slow cooling and vitrification. Successful blastocyst cryopreservation may be more consistently achieved with vitrification but optimal slow cooling can produce similar results. There are key limitations associated with the available evidence base, including a paucity of RCTs, limited reporting of live birth outcomes and limited reporting of detail which would allow assessment of the impact of differences in female age. While vitrification has a clear role in ART, we support continued research to establish optimal slow cooling methods which may assist in alleviating concerns over safety issues, such as storage, transport and the use of very high cryoprotectant concentrations.

Short Communication: Successful vitrification of mouse oocytes using the cryotop method with moderate cryoprotectant concentrations

Habibi, A., Hosseini, A., Farrokhi, N., Amidi, F., Carvalhais, I., Chaveiro, A. and Moreira da Silva, F. 2011. Short Communication: Successful vitrification of mouse oocytes using the cryotop method with moderate cryoprotectant concentrations. Can. J. Anim. Sci. 91: 385–388. The response of vitrified mouse MII oocytes in the presence of two concentrations of cryoprotectants [vit1 (15%: 7.5% dimethyl sulfoxide (DMSO)+7.5% ethylene glycol (EG) and vit2 (30%: 15% DMSO+15% EG)] was analyzed to investigate whether reducing cryoprotectant concentrations can affect oocyte survival after cryopreservation by the cryotop method. After thawing the survival, fertilization, cleavage and blastocyst rates were compared with unfrozen oocytes. It can be concluded that 15% cryoprotectant (7.5% DMSO+7.5% EG), instead of the commonly used 30% (15% DMSO+15% EG), could be helpful by moderating the probable toxic effects of vitrification solution in mouse oocyte during vitrification by cryotop.

The number of blastomeres in post-thawing embryos affects the rates of pregnancy and delivery in freeze-embryo-transfer cycles

PURPOSE

To observe the differences in pregnancy rates (PRs), delivery rates, and abortion rates associated with frozen-embryo-transfer (FET)-based use of post-thawing embryos with different numbers of blastomeres.

METHODS

959 FET cycles and 361 successful FET cycles performed between January 2007 and December 2007. Compare the PRs and abortion rates in post-thawing embryos with 8 blastomeres (8c), 7c, 6c, 5c, 4c,and 3c.

RESULTS

1. The total PRs of post-thawing 8c, 7c, 6c, 5c, 4c, and 3c embryos were 44.1%, 41.0%, 34.4%, 23.8%, 12.5%, and 0%, respectively (p < 0.05). 2. The abortion rates for the transferred embryos of the 8c, 7c, 6c, 5c, and 4c groups were 17.92%, 19.35%, 27.69%, 24%, 20%, respectively (p < 0.05).

CONCLUSION

The number of blastomeres in the post-thawing embryos is an important factor influencing the occurrence of pregnancy in FET procedures; however, the criterion that post-thawing embryos with 50% intact blastomeres will lead to pregnancy may not be valid.

The application and impact of cryopreservation of early cleavage stage embryos in assisted reproduction

The contribution of cryopreserved embryos to the overall outcomes achieved by a clinical assisted reproduction programme has increased in importance with the trend towards reducing the numbers of fresh embryos transferred following in vitro fertilisation. Although cryopreservation appears to fully preserve developmental potential in early cleavage stage embryos that survive intact, it results in a reduction in potential when blastomere loss occurs during freezing and thawing. Overall, it can be estimated that cryopreservation results in approximately a 30% reduction in the potential for pregnancy in a population of embryos. Both blastomere survival and post-thaw resumption of mitosis can act as markers of implantation potential in frozen/thawed embryos. Application of strict criteria for freezing embryos and transferring thawed embryos may enhance apparent success rates, but may also result in some pregnancy potential being discarded. The role of embryo cryopreservation in minimising the incidence of multiple pregnancy must be balanced with the need for efficiency in the quest to establish pregnancy.

Effect of laser-assisted hatching and necrotic blastomere removal on the development of vitrified-warmed four-cell mouse embryos

PURPOSE

To investigate the effect of laser-assisted hatching and necrotic blastomere removal on the development of vitrified-warmed mouse embryos.

METHODS

The vitrified-warmed four-cell stage mouse embryos were divided into five groups; vitrified intact with no laser-assisted hatching, vitrified intact with laser-assisted hatching, vitrified damaged with neither laser assisted hatching nor necrotic blastomere removal, vitrified damaged with laser-assisted hatching, and vitrified damaged with necrotic blastomere removal. Thereafter blastocyst formation, blastomere and apoptotic cell number within all groups were statistically compared.

RESULTS

The rate of blastocyst formation showed a significant improvement in the group vitrified intact with laser-assisted hatching. However, neither laser-assisted hatching nor necrotic blastomere removal can improve a delayed vitrified-warmed damaged embryos in term of blastocyst formation and total cell number. Nevertheless, apoptotic cell number was significantly reduced after application of both techniques.

CONCLUSIONS

Laser-assisted hatching can improve the development of vitrified-warmed intact four-cell stage mouse embryos, whereas necrotic blastomere removal has no significant effect on the development of vitrified-warmed four-cell stage damaged embryos.

Viability of frozen-thawed human embryos with one-two blastomeres lysis

OBJECTIVE

To assess the impact of one-two blastomeres lysis on the viability of thawed day 3 human embryos.

METHODS

A retrospective analysis was performed on 248 frozen-thawed embryo replacement cycles in which all embryos were frozen at day 3 at the seven-eight cell stage with <or=10% fragmentation.

RESULTS

Outcomes of transfer cycles with fully intact embryos (intact group) were compared with those in which all transferred embryos have lost one-two blastomeres (damage group). Comparable pregnancy rates (38.46% vs 38.64%), birth rates (34.62% vs 36.36%) and implantation rates (26.31% vs 26.25%) were obtained in intact and damage groups. These results were also not significantly different from mixed transfer cycles in which one intact embryo and one damaged embryo were transferred together.

CONCLUSION

The developmental potential of partially damaged cryopreserved human embryos with less than 25% cells loss is comparable to that of fully intact embryos. Presence of one-two lysed blastomeres in the thawed day 3 embryo does not appear to have a negative influence on the further development of the sibling intact cells.

A randomized controlled study of human Day 3 embryo cryopreservation by slow freezing or vitrification: vitrification is associated with higher survival, metabolism and blastocyst formation

BACKGROUND

The aim of this study was to compare two methods of cryopreservation for the cleavage-stage human embryo: slow freezing and vitrification.

METHODS

A total of 466 Day 3 embryos, donated with consent, underwent cryopreservation by either slow freezing in straws or vitrification using the cryoloop. The vitrification procedure did not include dimethyl sulfoxide, but rather employed ethylene glycol and 1,2-propanediol as the cryoprotectants. Survival, embryonic metabolism and subsequent development to the blastocyst were used to determine the efficacy of the two procedures.

RESULTS

Significantly, more embryos survived the vitrification procedure (222/234, 94.8%) than slow freezing (206/232, 88.7%; P < 0.05). Consistent with this observation, pyruvate uptake was significantly greater in the vitrification group, reflecting a higher metabolic rate. Development to the blastocyst was also higher following vitrification (134/222, 60.3%) than following freezing (106/206, 49.5%; P < 0.05). In a separate cohort of 73 patients who had their supernumerary embryos cyropreserved with vitrification, the resulting implantation rate and clinical pregnancy rate were 30 and 49%, respectively.

CONCLUSIONS

Analysis of metabolism revealed that vitrification had less impact on the metabolic rate of the embryo than freezing, which was reflected in higher survival rate and subsequent development in vitro. Excellent pregnancy outcomes followed the warming and transfer of vitrified cleavage-stage embryos. These data provide further evidence that vitrification imparts less trauma to cells and is, therefore, a more effective means of cryopreserving the human embryo than conventional slow freezing. Clinicaltrials.gov identifier: NCT00608010.

Severe cytoplasmic abnormalities of the oocyte decrease cryosurvival and subsequent embryonic development of cryopreserved embryos

BACKGROUND

Abnormalities of oocyte morphology affect embryo quality and viability. Whether morphological abnormalities of the oocyte influence cryosurvival and further development of derived embryos is not known. The aim of this study was to compare cryosurvival and progression to the blastocyst stage of frozen-thawed embryos derived from normal and abnormal oocytes.

METHODS

A total of 5292 Grade 1 and 2 embryos from 964 women were frozen, thawed and subsequently cultured up to the blastocyst stage. The study was performed on excess embryos from patients who did not opt for cryopreservation. Cryosurvival, progression to the blastocyst stage and hatching were correlated with morphological characteristics of the oocytes that embryos were derived from.

RESULTS

Presence of a cytoplasmic abnormality of the oocyte significantly decreased cryosurvival. This detrimental effect was more pronounced in embryos derived from oocytes with vacuolar cytoplasm or with central granulation. Furthermore, these embryos did not have the potential to develop into good quality blastocysts or reach the hatching stage. On the other hand, presence of a single extracytoplasmic abnormality of the oocyte did not affect cryosurvival and the potential to develop into good quality blastocysts. Grade 2 embryos derived from oocytes with irregular shape or a large perivitelline space had decreased cryosurvival. However when these embryos survived cryopreservation, their potential to develop good quality blastocysts or to reach hatching stage was unaffected.

CONCLUSIONS

Embryos derived from oocytes with vacuolar cytoplasm or central granulation do not seem to bear the potential to develop good quality blastocysts or to reach hatching stage after cryopreservation. The presence of extracytoplasmic abnormalities alone does not affect blastocyst development despite decreasing cryosurvival.

Resumption of mitosis in frozen-thawed embryos is not related to the chromosomal constitution

OBJECTIVE

To study the relation between the resumption of mitosis after thaw and chromosomal constitution in frozen-thawed embryos. In addition, to evaluate the correlation among the three parameters of resumption of mitosis after thaw, postthaw blastomere loss, and multinucleation.

DESIGN

Frozen-thawed embryos were morphologically evaluated at thaw and after 24 hours of culture. Then, fluorescence in situ hybridization (FISH) analysis, including enumeration of 13 chromosomes, was performed by using a combination of peptide nucleic acid and DNA probes.

SETTING

In vitro fertilization laboratory.

PATIENT(S)

Forty IVF and/or intracytoplasmic sperm injection patients.

INTERVENTION(S)

Embryo thawing, morphological evaluation, and fluorescence in situ hybridization analysis for aneuploidy screening.

MAIN OUTCOME MEASURE(S)

Resumption of mitosis, blastomere loss, multinucleation, and chromosome enumeration.

RESULT(S)

No difference was observed in the chromosomal constitution of embryos with and without resumption of mitosis. Neither was the postthaw blastomere loss connected to the chromosomal constitution. The resumption of mitosis was not associated with postthaw loss of blastomeres or with multinuclearity.

CONCLUSION(S)

Resumption of mitosis and blastomere loss of frozen-thawed embryos is not related to chromosome aberrations in the embryo. Further, the resumption of mitosis is not correlated with multinucleation. However, the high incidence of multinucleated embryos after thawing indicates that the freezing and thawing procedure may affect this condition.

Lysed cell removal promotes frozen–thawed embryo development

OBJECTIVE

To develop a mouse model to investigate the possible causes for increased success rates when lysed cells are removed from thawed embryos.

DESIGN

Experimental study.

SETTING

Clinical IVF laboratory.

INTERVENTION(S)

Assisted hatching, cell lysis, and removal of lysed cells.

MAIN OUTCOME MEASURE(S)

Embryonic growth rate and morphology.

RESULT(S)

The mouse embryos were divided into three groups; control (no cell lysis), group 1 (cell lysis and removal), and group 2 (cell lysis only). There was no significant difference in the initial number of blastomeres in each group or the number of cells lysed artificially in groups 1 and 2. The rate of embryonic development showed a significant delay in group 2 (7.97 +/- 4.92; control, 10.42 +/- 8.18; group 1, 5.74 +/-4.42; group 2). The embryo morphology on day 4 was significantly improved in group 1 and the control group when compared with group 2.

CONCLUSION(S)

Mouse embryos with artificially lysed cells after thawing had poorer developmental quality and growth rates compared with control embryos. However, removal of lysed cells restored the embryo's developmental potential to that of the control. Cell number and morphology was also significantly improved compared with embryos without lysed cell removal. These findings are consistent with human embryo development after thawing when lysed cells are present and thus mechanical lysis seems to be an appropriate method by which to further study frozen-thawed lysed cell removal.

Utilization of high-security straws for embryo freezing in an in vitro fertilization program: a prospective, randomized study

OBJECTIVE

To compare the outcome of frozen-thawed ET cycles where embryos had been stored in conventional versus ionomeric resin-based, high-security straws (HSSs).

DESIGN

Prospective, randomized study.

SETTING

Private assisted-reproduction unit.

PATIENT(S)

Three hundred and six freeze cycles, and 197 thaw cycles.

INTERVENTION(S)

Day 3 embryos (n = 1,268) were frozen, and 517 were thawed using HSSs. Alternately, day 3 embryos (n = 1,228) were frozen, and 505 were thawed using conventional straws.

MAIN OUTCOME MEASURE(S)

Cryosurvival, cleavage and morulae formation rates, and clinical pregnancy, implantation, and multiple pregnancy rates.

RESULT(S)

Although cycle characteristics did not show any differences, the cryosurvival rate was higher in the HSS group (94.7%) than in the conventional straw group (86%), as was the morulae formation rate (58.7% versus 42.7%). Despite a similar number of embryos being transferred, the clinical pregnancy rate (PR) was higher in the HSS group, but the difference lacked statistical significance (42.5% versus 31.2). Implantation rates (19.4% versus 11.4%) and multiple PRs (41.8% versus 16.6%) were significantly higher in the HSS group than in the conventional straw group.

CONCLUSION(S)

High-security straws are high effective in human embryo cryopreservation, because they provide higher cryosurvival and implantation rates, as well as a lower risk of cross-contamination compared to conventional straws.

Comparison of laser-assisted hatching and acidified Tyrode's hatching by evaluation of blastocyst development rates in sibling embryos: a prospective randomized trial

OBJECTIVE

To assess two zona drilling methods in terms of blastocyst development rates using sister embryos.

DESIGN

Prospective, randomized study. Sister embryos of 14 patients were randomly assigned on day 3 to acidified Tyrode's zona drilling or to laser zona drilling. After biopsy, subsequent embryo culture until the blastocyst stage (day 5) was performed.

SETTING

Private fertility center.

PATIENT(S)

Patients undergoing IVF-preimplantation genetic diagnosis.

INTERVENTION(S)

Embryo biopsy using either laser-assisted hatching or acidified Tyrode's hatching on sibling embryos and subsequent blastocyst development evaluation.

MAIN OUTCOME MEASURE(S)

Evaluation of blastocyst development in terms of degree of expansion and cell number in the inner cell mass and trophectoderm.

RESULT(S)

Blastocyst development rates (and blastocyst quality) were similarly high in both the acidified Tyrode's hatching group and the laser-assisted hatching group.

CONCLUSION(S)

Laser hatching does not impair embryonic development to the blastocyst stage, demonstrating that laser-assisted hatching is a suitable alternative to the use of acidified Tyrode's solution for zona drilling.

Laser-assisted hatching increases pregnancy and implantation rates in cryopreserved embryos that were allowed to cleave in vitro after thawing: a prospective randomized study

BACKGROUND

Cryopreservation of embryos may lead to zona hardening that may compromise in vivo hatching and implantation following thawing and transfer. Assisted hatching (AH) has been advocated as a means of assisting the natural hatching process and enhancing implantation.

METHODS

The aim of this study was to assess in a prospective randomized manner the effect of laser-assisted hatching (LAH) on implantation as well as clinical and multiple pregnancy rates (the primary outcome) after the transfer of frozen-thawed embryos. All embryos were thawed the day before transfer, and LAH was performed the next day on embryos that cleaved. Control group consisted of embryos that were transferred without AH.

RESULTS

The performance of LAH significantly increased implantation (9.9 versus 20.1%, P < 0.01), clinical pregnancy (27.3 versus 40.9, P < 0.05) and multiple pregnancy rates (16 versus 40.3%, P < 0.07). In the LAH group, significantly more excess embryos that were left in culture hatched in vitro.

CONCLUSIONS

LAH improves the outcome of frozen-thawed embryo transfer when performed before transfer on embryos that were allowed to cleave.

Blastocyst development of 4-cell mouse embryos after laser destruction of one blastomere with or without its microsurgical removal

AIM

To study the rate of blastocyst formation in 4-cell mouse embryos after laser destruction of one blastomere, with or without microsurgical removal of the destroyed blastomere.

METHODS

Mouse embryos were randomly allocated to two control and two experimented groups. Control embryos were either non-manipulated (117 embryos) or underwent laser ablation of zona only (114 embryos). Experimented embryos had laser destruction of zona and the adjacent blastomeres. Destroyed blastomeres were either left in situ (115 embryos) or were microsurgically removed (107 embryos). They were cultured in sequential media for 72 h and were assessed for cleavage/morula arrest and blastocyst formation rates.

RESULTS

Embryos arrested at cleavage/morula stages were higher when destroyed blastomeres remained in situ (30.4%) than when they were immediately removed (15.0%, P < 0.05). Blastocysts in the group with immediate removal of the destroyed blastomeres (85%) were significantly higher than when destroyed blastomeres were left in situ (69.6%, P < 0.05). Blastocyst formation in the repaired embryos was significantly lower than the non-manipulated (91.5%) and the manipulated controls (94.8%, P < 0.05). Hatching blastocysts were highest in control embryos with zonal ablation (72.8%). Proportions of hatching/hatched blastocysts in embryos, with or without removal of destroyed blastomeres, were not significantly different (39.3% and 33.9%, respectively). The percentage of embryonic loss during an attempt at microsurgical repair was 6.1%.

CONCLUSION

Microsurgical removal of destroyed blastomere was effective in restoring blastocyst development. It could reduce the rate of cleavage/morula arrest.

Removal of lysed blastomeres from frozen–thawed embryos improves implantation and pregnancy rates in frozen embryo transfer cycles

OBJECTIVE

To evaluate the effect of degenerated (lysed) blastomere removal on implantation and pregnancy rates in cleavage-stage cryo-embryo transfer (ET) cycles.

DESIGN

Randomized clinical trial.

SETTING

Private reproductive medical center.

PATIENT(S)

A total of 88 patients who received frozen-thawed ET, divided into two groups.

INTERVENTION(S)

Embryo freezing and thawing; opening of the zona pellucida and removal of cryodamaged blastomeres (in the study group), followed by same-day ET.

MAIN OUTCOME MEASURE(S)

Extent of survival of cleavage-stage embryos after the freeze-thaw procedure; embryo implantation and clinical pregnancies.

RESULT(S)

Oocyte number per patient, fertilization rate, embryo development rate (and quality), and freezing rates were similar in the two groups in the fresh cycle. In the control group, a total of 55 embryos (25%) of the 217 thawed remained fully intact, and 53 (26%) of the 207 in the study group remained intact. The average number of embryos transferred per group was similar (control, 3.4 +/- 0.9; study, 3.3 +/- 0.9). Implantation rates were 12% and 26% in the control and study groups, respectively. The clinical pregnancy rate was 23% in the control group and 64% in the study group when lysed cell removal was performed.

CONCLUSION(S)

The results show that pregnancy and implantation rates are higher in the study group; therefore, the removal of degenerated blastomeres may be beneficial to all patients who undergo cleavage-stage, frozen-thawed ET.

Developmental potential of fully intact and partially damaged cryopreserved embryos after laser-assisted removal of necrotic blastomeres and post-thaw culture selection

OBJECTIVE

Partially damaged frozen and thawed embryos are currently considered to have a lower viability than intact ones. This study was undertaken to compare the performance of intact frozen and thawed embryos with that of partially damaged embryos after removal of the necrotic blastomeres.

DESIGN

Observational clinical series.

SETTING

Private hospital.

PATIENT(S)

Three hundred twenty-six infertile couples undergoing frozen embryo transfer.

INTERVENTION(S)

Removal of necrotic blastomeres from frozen-thawed human embryos.

MAIN OUTCOME MEASURE(S)

Pregnancy and implantations rates.

RESULT(S)

Outcomes of frozen embryo transfer cycles in which all embryos were fully intact (group 1) were compared with those in which all embryos have lost 1-2 blastomeres (group 2) or 3-4 blastomeres (group 3). Laser-assisted hatching was performed in all embryos, and necrotic blastomeres were removed from partially damaged embryos on this occasion. Only embryos that resumed mitotic activity after thawing were transferred. Comparable clinical pregnancy rates (PR) (38.7%, 39.6%, and 29.4%), delivery rates (34.4%, 34.0%, and 29.4%), and implantation rates (21.6%, 21.4%, and 17.2%) were obtained in groups 1, 2, and 3, respectively.

CONCLUSION(S)

The developmental potential of partially damaged frozen and thawed embryos can be equivalent to fully survived embryos if the necrotic blastomeres are removed from the partially damaged embryos and only those of them that show post-thaw cleavage are selected for transfer.

Possible applications of a non-contact 1.48 μm wavelength diode laser in assisted reproduction technologies

Recently, one laser system has been introduced in IVF fulfilling all safety requirements, while achieving a high standard of reproducibility in terms of ablation diameter. This 1.48 microm wavelength indium-gallium-arsenic-phosphorus (InGaAsP) semiconductor laser offers a variety of laser applications to the embryologist. On the one hand, zona pellucida of oocytes or embryos can be manipulated in order to facilitate ICSI or biopsy and assist hatching, and on the other, spermatozoa may be paralysed or immobilized prior to usage. To conclude, the 1.48 microm diode laser provides a promising tool for the microdissection of subcellular targets. The diode laser stands out due to the rapidity, the simplicity and the safety of the procedure which is supported by healthy offspring after laser application.

Postthaw blastomere survival is predictive of the success of frozen?Thawed embryo transfer cycles

OBJECTIVE

To investigate the predictors of postthaw blastomere survival and the relationship of blastomere survival to the outcome of frozen-thawed embryo transfer (FET) cycles.

DESIGN

Retrospective study.

SETTING

An IVF unit in a tertiary care facility.

PATIENT(S)

Infertile women undergoing FET cycles with embryos cryopreserved on day 3 postinsemination.

INTERVENTION(S)

FET cycles.

MAIN OUTCOME MEASURE(S)

Embryo survival postthaw, pregnancy (PR), clinical pregnancy, and implantation rates.

RESULT(S)

A significant impact of postthaw blastomere survival on the outcome of FET cycles was noted. The thawed embryos in the low survival tertile resulted in significantly impaired implantation rate, clinical pregnancy rate, and PR compared to embryos in the high survival tertile. An inverse association was noted between serum P levels on the day of hCG administration and postthaw blastomere survival.

CONCLUSION(S)

We have demonstrated that postthaw blastomere survival is predictive of success of FET cycles. The relationship of poor postthaw embryo survival in the setting of elevated P is novel and not hitherto described.

Cumulative pregnancy rates after transfer of fresh and thawed embryos

Frozen-thawed embryo transfer is an effective procedure that allows further possibilities of pregnancy in addition to those obtained after the fresh in vitro fertilization (IVF). In our follow-up study we analysed all fresh embryo transfer procedures and every frozen-thawed embryo transfer performed from January 2000 to December 2001 evaluating the cumulative pregnancy rates. The study population was divided into two groups according to the female age: <38 years (group I) and >38 years (group II). All the best embryos were chosen for transfer and all the supernumerary good quality embryos were cryopreserved on the day of transfer. The embryos were then thawed and manipulated using a new technique. In group I, 527 patients (619 cycles) underwent fresh embryo transfer and in 232 of them (238 cycles) the embryos were frozen (44% per patients and 38.4% per cycle). In group II, 156 patients (193 cycles) underwent fresh embryo transfer and in 14 of them (15 cycles) the embryos were frozen (9% per patient and 7.8% per cycle). The pregnancy rate of group I patients that had their supernumerary embryos frozen (232 patients and 238 cycles) was 47.4% per cycle and 48.7% per patient whereas in the same population of group II patients (14 patients and 15 cycles) the clinical pregnancy rate was 35.7% per cycle and 38.5% per patients. The cumulative clinical pregnancy rate after transfer of fresh and thawed embryos was: group I, 74% per cycle and 76% per patients; group II, 42.8% per cycle and 46.1% per patient. Frozen-thawed embryo transfer is a cost-effective practice.

Effect of blastomere loss on the outcome of frozen embryo replacement cycles

OBJECTIVE

To assess the impact of survival of cryopreservation and thawing with all blastomeres intact on the outcome of frozen embryo replacement (FER) cycles.

DESIGN

Prospective observational study.

SETTING

University-affiliated tertiary referral assisted conception unit.

PATIENT(S)

The number of intact blastomeres before cryopreservation and after thawing was prospectively recorded in 1,687 cleavage-stage embryos thawed in 377 FER cycles. The cycles were categorized into two groups: group A (n = 184) included cycles in which all embryos transferred survived the cryopreservation and thawing process with all their original blastomeres intact; group B (n = 193) included cycles in which embryos transferred included at least one partially damaged embryo that has lost up to 50% of its original blastomere number.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Pregnancy and embryo implantation rates.

RESULT(S)

Groups A and B were comparable with respect to mean age at cryopreservation, mean number of oocytes retrieved and fertilized normally in the fresh cycle, and mean age at frozen transfer. No significant difference was found between the two groups with regard to mean number of frozen and thawed embryos per cycle and mean endometrial thickness reached before P supplementation. More embryos were transferred per cycle in group B than group A (2.4 +/- 0.6 vs. 2.1 +/- 0.6, respectively). However, the pregnancy and clinical pregnancy rates per cycle were significantly higher in group A than in group B (39.1% and 28.3% vs. 22.8% and 13.5%, respectively). The implantation rate was also higher in group A than in group B (17.3% vs. 8.1%, respectively).

CONCLUSION(S)

FER cycles in which all embryos transferred remained fully intact at thawing achieve a better outcome than those with at least one partially damaged embryo.