Reduction of high order multiples in frozen embryo transfers

The impact of embryo vitrification on placental histopathology features and perinatal outcome in singleton live births

STUDY QUESTION

Does embryo vitrification affect placental histopathology pattern and perinatal outcome in singleton live births?

SUMMARY ANSWER

Embryo vitrification has a significant effect on the placental histopathology pattern and is associated with a higher prevalence of dysfunctional labor.

WHAT IS KNOWN ALREADY

Obstetrical and perinatal outcomes differ between live births resulting from fresh and frozen embryo transfers. The effect of embryo vitrification on the placental histopathology features associated with the development of perinatal complications remains unclear.

STUDY DESIGN, SIZE, DURATION

Retrospective cohort study evaluating data of all live births from one academic tertiary hospital resulting from IVF treatment with autologous oocytes during the period from 2009 to 2017.

PARTICIPANTS/MATERIALS, SETTING, METHODS

All patients had placentas sent for pathological evaluation irrelevant of maternal or fetal complications status. Placental, obstetric and perinatal outcomes of pregnancies resulting from hormone replacement vitrified embryo transfers were compared with those after fresh embryo transfers. A multivariate analysis was conducted to adjust the results for determinants potentially associated with the development of placental histopathology abnormalities.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 1014 singleton live births were included in the final analysis and were allocated to the group of pregnancies resulting from fresh (n = 660) and hormone replacement frozen (n = 354) embryo transfers. After the adjustment for confounding factors the frozen embryo transfers were found to be significantly associated with chorioamnionitis with maternal (odds ratio (OR) 2.0; 95% CI 1.2-3.3) and fetal response (OR 2.6; 95% CI 1.2-5.7), fetal vascular malperfusion (OR 3.9; 95% CI 1.4-9.2), furcate cord insertion (OR 2.3 95% CI 1.2-5.3), villitis of unknown etiology (OR 2.1; 95% CI 1.1-4.2), intervillous thrombi (OR 2.1; 95% CI 1.3-3.7), subchorionic thrombi (OR 3.4; 95% CI 1.6-7.0), as well as with failure of labor progress (OR 2.5; 95% CI 1.5-4.2).

LIMITATIONS, REASONS FOR CAUTION

Since the live births resulted from frozen-thawed embryos included treatment cycles with previously failed embryo transfers, the factors over embryo vitrification may affect implantation and placental histopathology.

WIDER IMPLICATIONS OF THE FINDINGS

The study results contribute to the understanding of the perinatal future of fresh and vitrified embryos. Our findings may have an implication for the clinical decision to perform fresh or frozen-thawed embryo transfer.

STUDY FUNDING/COMPETING INTEREST(S)

Authors have not received any funding to support this study. There are no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Regenerative Medicine Approaches in Bioengineering Female Reproductive Tissues

Diseases, disorders, and dysfunctions of the female reproductive tract tissues can result in either infertility and/or hormonal imbalance. Current treatment options are limited and often do not result in tissue function restoration, requiring alternative therapeutic approaches. Regenerative medicine offers potential new therapies through the bioengineering of female reproductive tissues. This review focuses on some of the current technologies that could address the restoration of functional female reproductive tissues, including the use of stem cells, biomaterial scaffolds, bio-printing, and bio-fabrication of tissues or organoids. The use of these approaches could also be used to address issues in infertility. Strategies such as cell-based hormone replacement therapy could provide a more natural means of restoring normal ovarian physiology. Engineering of reproductive tissues and organs could serve as a powerful tool for correcting developmental anomalies. Organ-on-a-chip technologies could be used to perform drug screening for personalized medicine approaches and scientific investigations of the complex physiological interactions between the female reproductive tissues and other organ systems. While some of these technologies have already been developed, others have not been translated for clinical application. The continuous evolution of biomaterials and techniques, advances in bioprinting, along with emerging ideas for new approaches, shows a promising future for treating female reproductive tract-related disorders and dysfunctions.

Knockdown of pleiotrophin increases the risk of preeclampsia following vitrified-thawed embryo transfer

Preeclampsia (PE) in pregnancy is associated with vitrified-thawed embryo transfer. Pleiotrophin (PTN) is important in inflammation via its receptors. The aim of the present study was to determine the effect of PTN on the risk of PE following embryo transfer. An enzyme-linked immunosorbent assay was performed to determine the levels of tumor necrosis factor (TNF)-α and PTN in serum. The knockdown of PTN was conditionally induced by tamoxifen (tax) treatment. The tail-cuff method and Bradford assay were used to monitor blood pressure and the level of urine protein, respectively. The expression patterns of PTN, receptor protein tyrosine phosphatase β/ζ, (RPTPβ/ζ), syndecan-1 (SDC1), syndecan-3 (SDC3) and anaplastic lymphoma kinase (ALK) were determined by immunohistochemistry (IHC). Western blot analysis was performed to evaluate the expression level of PTN and its receptors. The risk of PE was elevated following embryo transfer in clinical and in the tax/PTN-/- group. It was found that the level of PTN increased when pregnancy progressed in normal conditions, however, the level of PTN was reduced in the PE mice. In addition, increases in TNF-α, blood pressure and urine protein were more marked in the PE mice that lacked PTN, compared with those in other PE mice. In addition, overlapping expression of PTN and its receptors in villous mesenchyme and fetal macrophages were identified using an IHC assay. However, the positive staining of PTN and its receptors was weaker or even absent in the PE mice. The protein level of RPTPβ/ζ was lower in the PE mice that lacked PTN than that in the other PE mice. The knockdown of PTN increased the risk of PE following vitrified-thawed embryo transfer, in which its receptors, particularly RPTPβ/ζ, may be involved.

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.

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.

Vitrification versus slow freezing gives excellent survival, post warming embryo morphology and pregnancy outcomes for human cleaved embryos

PURPOSE

The objective of this retrospective study was to evaluate the efficacy of vitrification and slow freezing for the cryopreservation of human cleavage stage embryos in terms of post-warming survival rate, post-warming embryo morphology and clinical outcomes.

METHODS

The embryos of 305 patients at cleavage stages were cryopreserved either with vitrification (153 patients) or slow-freezing (152 patients) methods. After warming; the survival rate, post-warmed embryo morphology, clinical pregnancy and implantation rates were evaluated and compared between the two groups.

RESULT(S)

In the vitrification group versus slow freezing group, the survival rate (96.9% vs. 82.8%) and the post-warmed excellent morphology with all blastomeres intact (91.8% vs. 56.2%) were higher with an odds ratio of 6.607 (95% confidence interval; 4.184-10.434) and 8.769 (95% confidence interval; 6.460-11.904), respectively. In this group, the clinical pregnancy rate (40.5% vs. 21.4%) and the implantation rate (16.6% vs. 6.8%) were also higher with an odds ratio of 2.427 (95%confidence interval; 1.461-4.033) and 2.726 (95% confidence interval; 1.837-4.046), respectively.

CONCLUSION(S)

Vitrification in contrast to slow freezing is an efficient method for cryopreservation of human cleavage stage embryos. Vitrification provides a higher survival rate, minimal deleterious effects on post-warming embryo morphology and it can improve clinical outcomes.

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.

Comparison of open and closed methods for vitrification of human embryos and the elimination of potential contamination

Survival and development of human embryos was compared following slow cooling versus vitrification involving more than 13,000 vitrified embryos. In addition, the efficacy of an open system, the Cryotop, and a closed vitrification system, the CryoTip(trade mark), were compared using human blastocysts. One hundred percent of vitrified human pronuclear stage embryos survived and 52% developed to blastocysts as compared with 89% survival and 41% blastocyst development after slow cooling. Similar survival rates were seen with vitrification of 4-cell embryos (98%) as compared with slow cooling (91%). Furthermore, 90% of vitrified blastocysts survived and resulted in a 53% pregnancy rate following transfer, as compared with 84% survival and 51% pregnancy rates following slow cooling. All corresponding values were significantly different. When the closed and open vitrification systems were compared, no difference was found with regard to supporting blastocyst survival (93 and 97% for CryoTip and Cryotop respectively), pregnancies (51 versus 59% respectively) and deliveries (48 versus 51% respectively). Vitrification is a simple, efficient and cost-effective way to improve cumulative pregnancy rates per cycle. The use of the closed CryoTip system eliminates the potential for embryo contamination during cryopreservation and storage without compromising survival and developmental rates in vitro and in vivo.

Towards defining parameters for a successful single embryo transfer in frozen cycles

BACKGROUND

Twin pregnancies in IVF should be avoided by transferring embryos one at a time, even for frozen cycles. In this study, we investigated the effect of blastomere lysis and cleavage in singleton frozen embryo transfer (sFET) cycles. Outcomes were compared with the transfer of two embryos in frozen transfer cycles (dFET).

METHODS

A retrospective analysis was performed on 891 FET cycles, involving 404 sFET and 487 dFET cycles.

RESULTS

Overall, in sFET cycles, the pregnancy and implantation rates were 8.9 and 8.7%. When blastomere lysis was more than 25% but no greater than 50%, the pregnancy and implantation rates were 3.2%. If blastomere lysis was greater than 50% there were no pregnancies. If blastomere lysis was less than 25%, but with no cleavage, the pregnancy and implantation rates were 4.1%. The results significantly improved (P = 0.007) in the group with less than 25% lysis, when cleavage occurred. The pregnancy and implantation rates for this group were 17.3 and 16.6%. This was not significantly different from unselected two embryo transfers (22 and 12.7%,P = 0.2 and 0.19, respectively). There were 21 twins with dFET (19.6% of pregnancies) and none in sFET.

CONCLUSION

Both blastomere lysis and cleavage affect the outcome in sFET. To avoid the risk of twins, sFET should be considered when the embryo shows less than 25% blastomere lysis and at least one blastomere cleaves.

Contribution of embryo cryopreservation to elective single embryo transfer in IVF–ICSI

Single embryo transfer is the best way to reduce the risk of multiple pregnancy in IVF-intracytoplasmic sperm injection (ICSI). Between June 2002 and December 2004, all patients (first cycle, female age <38 years) were offered the choice between having one (SET) or two (DET) embryos transferred. Among 493 couples, 428 had at least two good quality embryos, and among them, 32% opted for SET. The SET and DET populations were not comparable (patients in the SET group were younger and had more oocytes retrieved), and therefore a paired, case-control analysis was performed involving 130 SET couples and 130 DET couples, matched according to the female partners' ages and the numbers of embryos available. All of the SET patients, and 82% of the DET group, had at least one embryo cryopreserved, (3.9 versus 2.8 embryos). The option of SET was continued for the frozen-thawed embryo transfers. The pregnancy rate following embryo transfer was significantly lower after SET compared with DET for both fresh (27.6 versus 36.9%; P < 0.05) and frozen-thawed (14.4 versus 23.5%) embryos. However, the cumulative live birth rates following the transfer of fresh and frozen embryos were identical between the two groups (43 versus 45%), with a high prevalence of twins following DET (34 versus 0%).