Embryonic factors affecting outcome from single cryopreserved embryo transfer

doi:10.1016/S1472-6483(10)60674-8

Reproductive BioMedicine Online

Volume 14, Issue 6, 2007, Pages 718-723

https://doi.org/10.1016/S1472-6483(10)60674-8 Get rights and content

Abstract

Multiple pregnancy minimization by single embryo transfer is becoming more prevalent, but is less common in the case of cryopreserved embryos. This study defines embryonic characteristics in single cryopreserved embryo transfers associated with success rates equivalent to those achieved when transferring two cryopreserved embryos. In a retrospective analysis of 6916 cryopreserved day-2 embryo transfer procedures, transfer of two cryopreserved embryos resulted in higher clinical pregnancy rates when compared with transfer of a single thawed embryo but was also associated with elevated multiple pregnancy rates (26.7% in women under 36). Optimal outcome (implantation rate of 30.9%) from single cryopreserved embryo transfer (SCET) in women under 36 was associated with cryopreservation at the 4-cell stage, loss of fewer than two blastomeres and subsequent cleavage of at least two surviving blastomeres. In comparison, transfer of two cryopreserved embryos in women under 36 resulted in pregnancy and implantation rates of 25.5 and 16.1% respectively. Interestingly, in cryopreserved 4-cell stage embryos, loss of a single blastomere did not reduce implantation potential and cleavage of only a single post-thaw blastomere was not indicative of increased implantation potential. Establishment of these critical thresholds provides a rational basis for SCET.

Section snippets

Dr David Edgar is a graduate of the University of Glasgow and University College London. He completed a post-doctoral fellowship in Cambridge before being appointed as Lecturer at the University of Dundee where he established the Assisted Conception Laboratories in the 1980s. Since 1994 he has been Scientific Director of Reproductive Services, Melbourne IVF, Australia and is also Senior Lecturer in the Department of Obstetrics and Gynaecology, University of Melbourne. His main scientific

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Cited by (39)

Natural cycle for frozen-thawed embryo transfer: Spontaneous ovulation or triggering by HCG
2018, Gynecologie Obstetrique Fertilite et Senologie
Comparer l’issue des transferts d’embryons congelés (TEC) réalisés lors d’un cycle naturel en fonction de l’administration ou non d’hCG recombinante (r-hCG) pour déclencher l’ovulation.
Cette étude rétrospective a inclus l’ensemble des patientes prises en charge pour un TEC en cycle naturel sur une période de 1 an. Les patientes monitorées jusqu’à la détection d’un pic de LH formaient le groupe A (n = 38), les patientes ayant reçu une injection de r-hCG afin de déclencher artificiellement l’ovulation constituaient dans le groupe B (n = 43). Tous les embryons avaient été conservés par vitrification. Aucun soutien de la phase lutéale n’avait été mis en place. Nous avons comparé l’issue des TEC entre les 2 groupes.
Après vérification de la comparabilité des 2 groupes, il n’existe pas de différence significative pour les taux d’implantation, de grossesse clinique et de naissance vivante (31 % vs 45 %, 32 % vs 51 % et 21 % vs 32 % respectivement pour les groupe A et B). Le nombre de monitorage était significativement plus faible dans le groupe B (1,9 ± 0,8 versus 2,5 ± 1, p = 0,006)
Bien qu’aucun consensus ne soit encore établi, le cycle naturel semble aujourd’hui s’imposer chez les patientes normo-ovulantes mais le mode de déclenchement de l’ovulation reste débattu. Dans notre étude, le déclenchement par r-hCG, réalisé en présence de critères stricts, semble offrir de bons résultats tout en réduisant les contraintes et le coût du protocole.
To compare frozen-thawed embryo transfer (FET) outcomes in natural cycles according to ovulation induction: spontaneous versus recombinant human chorionic gonadotrophin (r-hCG) triggering.
This retrospective study included all patients monitored for natural cycle FET during one year. When serial monitoring were performed until spontaneous LH rise, patients were included in group A (n = 38) whereas those receiving r-hCG for ovulation triggering formed group B (n = 43). All embryos had been cryopreserved by a vitrification method following a previous IVF cycle. No luteal phase support had been given. We compared outcomes between the 2 groups.
After checking groups comparability, we didn’t find significant difference for the implantation rate, clinical pregnancy rate and live birth (31% vs 45%, 32% vs 51% et 21% vs 32%, respectively for group A and B). The number of monitoring was significantly lower in group B (1,9 ± 0,8 versus 2,5 ± 1, P = 0,006).
Although no consensus has been yet established, natural cycle seems indicated for normo-ovulating patients but the question of ovulation induction is still debated. In our study, triggering ovulation by r-hCG, respecting strict criteria, seems provide good results while reducing both protocol's constraints and cost.
The impact of blastomere survival rates on developmental competence of cryo-thawed Day 2 embryos
2016, European Journal of Obstetrics and Gynecology and Reproductive Biology
The aim of the present study is to investigate the effect of embryonic blastomere loss, following cryopreservation and thaw of Day 2 embryos in an assisted reproductive technology (ART) setting, on pregnancy outcome and fetal development.
This is a retrospective analysis performed on 3553 slow frozen-thawed Day 2 embryos, of all IVF/ICSI thawing cycles carried out during the 11 year study period. Of these thawed embryos, 628 underwent SET on Day 3 of embryo development. We measured the influence of several laboratory parameters on blastomere loss after thaw including: cell stage at cryopreservation, blastomere loss post-thaw, ability to resume mitosis and the rate of overnight cleavage.
There is an association between cell number on day of freeze and embryonic survival post-thaw; 3 cell (77.4%), 4 cell (92.1%), 5 cell (81.4%) and 6 cell (86.5%) embryos (p < 0.05). We found a significant association between the rate of overnight cleavage and positive hCG and implantation rate (p-value <0.05), while there is no association with live birth rate (p-value 0.242). Embryos with 100% blastomere survival have significantly higher cleavage rates, positive hCG, implantation and live birth rates than embryos which experienced blastomere loss (p < 0.05). However, blastomere survival has no impact on miscarriage rate or the observed newborn birth weight (3.85 ± 0.77 kg).
In the present study we demonstrate, for the first time, that although it is optimal to select an embryo with 100% blastomere survival, transfer of an embryo with ≥50% blastomeres intact post-thaw does not influence the development of the baby, as indicated by weight at birth.
Delivery rates after elective single cryopreserved embryo transfer related to embryo survival
2015, European Journal of Obstetrics and Gynecology and Reproductive Biology
The objective of this study was to assess if eSCET (elective Single Cryopreserved Embryo Transfer) outcome is related to blastomere survival rate. The final objective was to avoid multiple pregnancies and offer the best chances to women to achieve pregnancy even during their frozen–thawed embryo transfer (FET) cycles.
Patients were included in this prospective observational study if they met the following criteria: (i) women age <37 years old; (ii) IVF of ICSI cycle rank ≤2, (iii) eSET proposed during fresh embryo transfer cycle and (iv) ≥1 good quality cryopreserved embryos available (<20% fragmentation and 4–5 blastomeres at day-2 or 7–9 blastomeres at day-3). Live birth rates (LBR) were compared into eSCET groups according to embryo survival (partially damaged or intact transferred embryo).
We observed among selected patients, that partial loss of blastomeres (1 blastomere for day-2 embryos, 1 or 2 blastomeres for day-3 embryos) following FET cycles did not affect LBR compared with intact embryo.
These results underline the relevance of eSCET as a strategy to reduce multiple pregnancies frequency without reducing LBR.
Extended culture of vitrified-warmed embryos in day-3 embryo transfer cycles: A randomized controlled pilot study
2013, Reproductive BioMedicine Online
Citation Excerpt :
Those embryos with >8 cells implied further development and higher implantation potential. Among embryonic factors associated with successful implantation, single cryopreserved embryo transfers have indicated that embryos with subsequent cleavage are associated with higher success rates (Edgar et al., 2007; Van der Elst et al., 1997; Ziebe et al., 1998), findings that are consistent with the current study. In the EC group, prewarmed embryos probably reached the hatched stage early during the implantation window, allowing the possibility of early implantation.
Synchronization between embryonic stage and endometrium is vital to achieve a successful pregnancy. The objective of this study was to assess the implantation, clinical pregnancy and live birth rates of cryopreserved embryo transfer cycles using embryos after extended culture for 16 h. A prospective randomized controlled pilot study was performed on women who underwent vitrified–warmed embryo transfer. Of the 540 women assessed for eligibility, 479 were randomly allocated to either extended culture for 16–18 h (EC group, n = 242) or conventional culture for 2 h (control group, n = 237). Endometrial preparation was the same in both groups. No significant differences were found between the extended culture and control groups respectively in clinical pregnancy rate per embryo transfer (42.48% versus 40.95%), implantation rate (21.79% versus 20.82%) or live birth rate per embryo transfer (37.61% versus 34.05%); however, the spontaneous reduction rate was lower in the extended culture group (10.04% versus 20.80%; P = 0.032) In conclusion, extended culture of day-3 cleavage embryos for 16 h would not influence the pregnancy outcome of day-3 cryopreserved embryo transfer cycles.
Synchronization between embryonic stage and endometrium is vital to achieve a successful pregnancy and most implantation failures are possibly associated with inadequate endometrial receptivity or defects in the embryo–endometrium crosstalk. In this paper, we regulated synchronization via extended post-warming culture using conventional day-3 endometrial preparation in vitrified–warmed embryo transfer cycles and observed the clinical outcomes, including implantation, clinical pregnancy and live birth rates. Extended post-warming culture did not influence the clinical outcomes. This study implies that transfer of embryos at an advanced developmental stage may not affect implantation. This gives clinical doctors more flexibility in the performance of routine cryopreserved embryo transfer cycles.
The fate of frozen human embryos when transferred either on the day of thawing or after overnight culture
2012, Asian Pacific Journal of Reproduction
To study the performance of thawed zygotes and cleavage stage embryos transferred either on the day of thaw or after overnight culture.
A retrospective study of 864 frozen embryo transfer cycles. Cryosurvival rates per thawed embryo and implantation rates were analysed for embryos frozen on Day 1, Day 2 or Day 3 relative to oocyte collection (Day 0) and transferred on the day of thaw or after overnight culture, together with clinical pregnancy rates and prevalence of multiple gestations.
Survival of Day 3 embryos was significantly lower than those frozen on Day 1 (P=0.017) or Day 2 (P=0.015). Following overnight culture, resumption of mitosis of zygotes was more frequent than Day 2 (P=0.000) which are in turn higher than Day 3 (P=0.000) embryos. The implantation rate for Day 2 embryos dividing overnight was significantly higher than those that did not divide for women <35 yrs (P=0.001) but not those women <35 yrs (P=0.055). There were no differences in the implantation rates for those dividing or not after culture, for embryos frozen on Day 3 for women <35 yrs (P=0.254) or <35 yrs (P=0.403).
Later cleavage stage post-thaw embryos survive and resume mitosis less frequently compared to earlier stages. Embryos not resuming mitosis after culture overnight can implant, particularly Day 3 embryos, suggesting that they can further increase the cumulative pregnancy rate per oocyte collection and that discarding them is wasteful. Overnight culture is best used for logistical reasons rather than a strategy to improve pregnancy rates.
The Alpha consensus meeting on cryopreservation key performance indicators and benchmarks: Proceedings of an expert meeting
2012, Reproductive BioMedicine Online
Citation Excerpt :
Traditionally, KPIs dealing with embryo cryosurvival are based on the proportion of thawed embryos with (i) 100% and (ii) ⩾50% of the blastomeres intact. It was suggested that based on published evidence (e.g. Edgar et al., 2007), the lower rate of cryosurvival could be ⩾67% or ⩾75%, rather than ⩾50%, but it was the consensus to retain the traditional definitions for the development of the current KPIs, with a future KPIs to be the proportion of intact blastomeres across all embryos thawed. Accordingly, the competence and benchmark KPI values for morphological cryosurvival were based on the proportion of frozen and vitrified cleavage-stage embryos in which all of the blastomeres were intact (E1, Table 3) and for embryos with at least 50% intact blastomeres (E2, Table 3).
This proceedings report presents the outcomes from an international workshop designed to establish consensus on: definitions for key performance indicators (KPIs) for oocyte and embryo cryopreservation, using either slow freezing or vitrification; minimum performance level values for each KPI, representing basic competency; and aspirational benchmark values for each KPI, representing best practice goals. This report includes general presentations about current practice and factors for consideration in the development of KPIs. A total of 14 KPIs were recommended and benchmarks for each are presented. No recommendations were made regarding specific cryopreservation techniques or devices, or whether vitrification is ‘better’ than slow freezing, or vice versa, for any particular stage or application, as this was considered to be outside the scope of this workshop.

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ArticleEmbryonic factors affecting outcome from single cryopreserved embryo transfer

Abstract

Section snippets

Lancet

Fertility and Sterility

European Journal of Obstetrics and Gynecology and Reproductive Biology

Molecular and Cellular Endocrinology

Fertility and Sterility

Reproductive BioMedicine Online

Fertility and Sterility

Reproductive BioMedicine Online

Reproductive BioMedicine Online

Blastocyst formation and cell numbers in human frozen–thawed embryos following extended culture

Human Reproduction

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

Human Fertility

The influence of prefreeze growth rate and blastomere number on cryosurvival and subsequent implantation of human embryos

Journal of Assisted Reproduction and Genetics

A quantitative analysis of the impact of cryopreservation on the implantation potential of human early cleavage stage embryos

Human Reproduction

Multiple gestation pregnancy

Human Reproduction

Article
Embryonic factors affecting outcome from single cryopreserved embryo transfer