Correlation between embryological factors and pregnancy rate: development of an embryo score in a cryopreservation programme

Impacts of different culture times on pregnancy outcomes after thawing of cleavage stage embryos

OBJECTIVE

This study assessed the impacts of in vitro culture times of cleavage embryos on clinical pregnancy outcomes.

METHODS

This retrospective cohort study was performed at the Reproductive Medicine Department of Hainan Modern Women and Children's Hospital in China between January 2018 and December 2022. Patients who first underwent frozen embryo transfer with in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) cycles on day 3 were included. According to the time of embryo culture after thawing, the embryos were divided into long-term culture group(18-20 h) and short-term culture group (2-4 h). The clinical pregnancy rate was regarded as he primary outcome. To minimize confounding factors and reduce selection bias, the propensity score matching was used to balance the effects of known confounding factors and to reduce selection bias. Stratified analyses and multiple logistic regression analyses were used to evaluate the risk factors affecting the clinical pregnancy outcomes after matching.

RESULTS

General characteristics between two groups were comparable after matching. In the long-term culture group, 266/381 (69.81%) embryos had more than 10 blastomeres, and 75/381 (19.68%) reached the morula stage. After overnight culture, the implantation rate (27.97% vs. 14.28%, P = 0.018) and clinical pregnancy rate (38.46% vs. 22.5%, P = 0.05) were increased in the group with proliferating blastomeres. The long-term culture group trended to have a higher clinical pregnancy rate compared with the short-term culture group (35.74% vs. 29.79%). No statistical differences in clinical pregnancy outcomes between the two groups were observed after matching, including the rates of implantation (25.46% vs23.98%), miscarriages (25% vs. 22.85%), ongoing pregnancy rate (76.2% vs. 77.15%) and live birth rate (26.8% vs. 22.98%). Stratified analyses were performed according to the age of the patients. After matching, there were no significant differences in the clinical pregnancy, implantation and miscarriage rates between the two groups for patients > 35 or ≤ 35 years of age. Subgroup analyses were performed according to the quality of the transferred embryos. There were no significant differences in the clinical outcomes, between two groups after embryos transferred with the same quality. Multivariate Logistic regression analysis was used to evaluate the influencing factors of clinical pregnancy outcomes after matching. Culture time was not found to be an independent predictor for clinical pregnancy [OR 0.742, 95%CI 0.487 ~ 1.13; P = 0.165]. The age of oocyte retrieval [OR 0.906, 95%CI 0.865 ~ 0.949; P <0.001] and the number of high-quality embryos transferred [OR 1.787, 95%CI 1.256 ~ 2.543; P = 0.001] were independent factors affecting clinical pregnancy outcomes.

CONCLUSIONS

In vitro 18-20 h culture of embryos with either good-or non-good-quality will not adversely affect the clinical pregnancy.

A proof of concept for a deep learning system that can aid embryologists in predicting blastocyst survival after thaw

The ability to understand whether embryos survive the thaw process is crucial to transferring competent embryos that can lead to pregnancy. The objective of this study was to develop a proof of concept deep learning model capable of assisting embryologist assessment of survival of thawed blastocysts prior to embryo transfer. A deep learning model was developed using 652 labeled time-lapse videos of freeze-thaw blastocysts. The model was evaluated against and along embryologists on a test set of 99 freeze-thaw blastocysts, using images obtained at 0.5 h increments from 0 to 3 h post-thaw. The model achieved AUCs of 0.869 (95% CI 0.789, 0.934) and 0.807 (95% CI 0.717, 0.886) and the embryologists achieved average AUCs of 0.829 (95% CI 0.747, 0.896) and 0.850 (95% CI 0.773, 0.908) at 2 h and 3 h, respectively. Combining embryologist predictions with model predictions resulted in a significant increase in AUC of 0.051 (95% CI 0.021, 0.083) at 2 h, and an equivalent increase in AUC of 0.010 (95% CI -0.018, 0.037) at 3 h. This study suggests that a deep learning model can predict in vitro blastocyst survival after thaw in aneuploid embryos. After correlation with clinical outcomes of transferred embryos, this model may help embryologists ascertain which embryos may have failed to survive the thaw process and increase the likelihood of pregnancy by preventing the transfer of non-viable embryos.

Extended culture of cleavage embryo to blastocyst embryo is among the good predictors of successful outcome in vitrified-thawed ICSI cycles

Background

Previous studies showed that top-quality embryo transfer (ET), number of transferred embryos, endometrial preparation with natural cycles or mild stimulation, and female BMI independently affected the outcome in frozen-thawed ET. However, the effect of culturing thawed cleavage embryos to blastocyst stage on the outcome was not sufficiently elucidated. Our objective is to evaluate the role of this extended culturing as predictor of cycle outcome in vitrified-thawed ICSI cycles.

Materials and methods

One thousand forty-two consecutive cycles of vitrified-thawed ET done in a single IVF unit [Mansoura Integrated Fertility Centre (MIFC)] were reviewed during a period from 2014 to 2017. Endometrial preparation methods were natural, stimulation by antiestrogen and/or gonadotropins, or replacement using sequential estradiol (E2) and progesterone (P4). The primary outcome was the clinical pregnancy rate while the secondary outcome was the chemical and ongoing pregnancy rate.

Results

Overall clinical pregnancy rate (CPR) is 298/1042 is 28.5%, chemical pregnancy rate (326/1042) 31.3%, and ongoing pregnancy rate (167/615) 27.2%. Comparing clinically pregnant (n = 298) and non-pregnant (n = 744) showed, respectively, the following: age 28.76 ± 5.0, 28.85 ± 5.18 (p = 0.8); BMI 31.06 ± 5.9, 32.45 ± 5.9 (p = 0.002); infertility duration 4.17 ± 3.2, 4.6 ± 3.5 (p = 0.038); endometrial thickness 10.82 ± 1.6, 10.13 ± 2.06 (p = 0.0001); and no. of ET 3.35 ± 1.5, 3.12 ± 1.60 (p = 0.035). The clinical pregnancy rate when vitrification was done on cleavage embryos was 198/502 (39.4%), and when vitrification done on blastocyst stage 100/ 536 (18.7%) (P < 0.0001); endometrial preparation: natural 72/240(29.1%), stimulated 204/680 (30.0%) replacement 17/90 (18.8%) (p = 0.09); extended culture of cleavage embryos to blastocyst stage: clinical pregnancy rate 116/194 (59.7%) chemical pregnancy rate 125/194 (64.1%), ongoing pregnancy rate 87/165 (52.7%) and non extended culture clinical pregnancy rate 182/848 (21.4%), chemical pregnancy rate 201/848 (23.7%), and ongoing pregnancy rate 80/450 (17.7%) (P < 0.0001).

Conclusion

Top-quality ET, number of transferred embryos and extended culture of cleavage embryos to blastocyst stage, cleavage embryos but not infertility duration, BMI, endometrial thickness, or hCG trigger of ovulation independently predict successful outcome in frozen cycle ET and extended culture of cleavage embryos significantly improved clinical and chemical and ongoing pregnancy rates.

Medroxyprogesterone acetate versus ganirelix in oocyte donation: a randomized controlled trial

STUDY QUESTION

Is oral medroxiprogesterone acetate (MPA) non-inferior compared to ganirelix with respect to the number of mature oocytes (MII) retrieved at ovum pick-up (OPU) in oocyte donation cycles?

SUMMARY ANSWER

MPA is comparable to ganirelix in terms of number of MII retrieved at OPU in oocyte donation cycles.

WHAT IS KNOWN ALREADY

Oral treatment with MPA inhibits the pituitary LH surge during ovarian stimulation in infertile patients. Because of its negative effect on the endometrium, MPA suppression is combined with freeze-all. Published reports indicate that both the number of MII retrieved and pregnancy rates from these oocytes are comparable to short protocol of GnRH agonists during IVF cycles with freeze-all. MPA might allow for more comfortable and cost-effective ovarian stimulation.

STUDY DESIGN, SIZE, DURATION

Randomized clinical trial, open-label, single center, to assess the non-inferiority of MPA (10 mg/day) versus ganirelix (0.25 mg/day) from Day 7, in ovarian stimulation cycles triggered with triptoreline acetate. Trigger criterion was ≥3 follicles of diameter >18 mm.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Overall, 252 oocyte donors were selected (eligible), 216 were randomized and 173 reached OPU: 86 under MPA and 87 under ganirelix. The main outcome was the number of MII retrieved at OPU. Secondary outcomes were embryological laboratory outcomes and reproductive outcomes in recipients. The study was powered to test that the lower limit of the 95% confidence interval of the difference in retrieved MII between groups will be above the non-inferiority limit of -3. Differences were tested using a two-sided Student's t-test or a Pearson's Chi2 test, as appropriate.

MAIN RESULTS AND THE ROLE OF CHANCE

All participants were in their first cycle of oocyte donation. On average, donors were 24 (SD 4.5) years old and with a BMI of 23 (SD 2.9) kg/m2. Duration of stimulation was similar in both groups (11.2 days), as well as the total gonadotropin dose up to trigger (2162 IU in MPA and 2163 IU in ganirelix). The number of MII retrieved was no different: 15.1 (SD 8.3) with MPA and 14.6 (SD 7.0), 95% CI of the difference -2.78, -1.83 excluding the pre-defined non-inferiority limit (-3). Recipients and embryo transfer (ET) characteristics were also similar between groups. The average age of recipients was 42 (SD 4.8) years and the BMI was 24 (SD 4.4) kg/m2. The mean number of MII assigned to each recipients was 6.7 (SD 1.2) in MPA and 6.6 (SD 1.2) in ganirelix (P = 0.58). MII were fertilized with partner sperm in 84% cycles overall and fertilization rate was 76% in MPA versus 74% in ganirelix (P = 0.34). Overall, there was 54% of double ET and 46% of single ET, with 40% of ETs were performed in D5. In spite of similar recipients and cycle characteristics, reproductive outcomes were unexpectedly lower with MPA. Biochemical pregnancy rate was 44 versus 57% (P = 0.023); clinical pregnancy rate 31 versus 46% (P = 0.006); ongoing pregnancy rate 27 versus 40%, (P = 0.015) and live birth rate 22 versus 31%, (P = 0.10).

LIMITATIONS, REASONS FOR CAUTION

Although oocyte recipient and ET characteristics are similar among groups, this RCT has been designed under a hypothesis of non-inferiority in the number of MII obtained and recipients were not randomized; therefore, the reproductive outcomes in recipients should be evaluated with extreme caution.

WIDER IMPLICATION OF THE FINDINGS

Ovarian stimulation using MPA for prevention of LH surge yields comparable number of MII oocytes compared to ganirelix in oocyte donation cycles. The unexpected finding in reproductive outcomes should be further investigated.

STUDY FUNDING/COMPETING INTEREST(S)

None to report.

TRIAL REGISTRATION NUMBER

EudraCT number: 2015-004328-73; ClinicalTrials.gov Identifier: NCT02796105.

TRIAL REGISTRATION DATE

29 September 2015 (EudraCT); 9 June 2016 (ClinicalTrials.gov).

DATE OF FIRST PATIENT’S ENROLLMENT

The date of enrollment of the first participant was 07 July 2016, and the last participant last visit in the study was on 10 July 2017.

Does Overnight Culture of Cleaved Embryos Improve Pregnancy Rate in Vitrified-Warmed Embryo Transfer Programme?

Background

Vitrification is a routine procedure in assisted reproductive technique (ART) lab. However, there is widespread variability between protocols of different centres. The aim of this study was to compare the chemical pregnancy, clinical pregnancy and live birth rates between one-day embryo culture and immediate transfer for frozen-thawed embryo transfer (FET) cycles.

Methods

In this cohort retrospective study, 366 FET cycles were divided into two groups: Group A, the embryos were warmed one day before transfer, and were cultured overnight; Group B, the embryos were warmed on the same day of transfer, at least were cultured 1 h before embryo transfer (ET). Chemical and clinical pregnancy and live birth rates were compared between two groups.

Results

The chemical pregnancy was higher in group A than B (37.9% versus 28.9%), but this difference was not significant (P = 0.07). Clinical pregnancy (30.8% versus 24.1%) and live birth (19.8% versus 22.05%) were similar in group A and B, (P = 0.15), and (P = 0.8). Conclusion: In conclusion, overnight culture and confirmation of mitosis resumption was not essential for FET cycles in vitrification method.

Serum estradiol level on trigger day impacts clinical pregnancy rate in modified natural frozen embryo transfer cycles

OBJECTIVE

To examine the predictive value of serum estradiol and progesterone on the day of human chorionic gonadotropin (hCG) administration and embryo transfer for clinical pregnancy rate in modified natural-cycle frozen embryo transfer (NC-FET).

METHODS

In a longitudinal prospective study, all eligible women who underwent NC-FET cycles with hCG triggering in Royan Institute, Tehran, Iran, from June 1, 2015, to December 31, 2016, were evaluated. Serum estradiol and progesterone levels were measured at menstrual cycle initiation, on day of trigger with hCG, on day of embryo transfer, and in pregnant women every 7 days until the observation of a gestational sac with embryonic heartbeat.

RESULTS

In total, 101 modified natural FET cycles were assessed, and the clinical pregnancy and live birth rates achieved were 34 (33.6%) and 32 (31.6%), respectively. The changes in estradiol level during early pregnancy showed an increase by an average of 200 pg/mL per week. Multivariable logistic regression analysis showed that only the estradiol level on the hCG day was a significant predictive variable for clinical pregnancy following NC-FET (P=0.04).

CONCLUSION

Estradiol level on the day of hCG trigger predicted the clinical pregnancy rates after modified NC-FET; this likely mirrored the developmental competence of the corpus luteum and an appropriate luteal structure-function.

Effect of day 3 embryo morphometrics and morphokinetics on survival and implantation after slow freezing-thawing and after vitrification-warming: a retrospective cohort study

BACKGROUND

Morphometric and morphokinetic evaluation of in vitro cultured human embryos allows evaluation without time restriction and reduces intra- and inter-observer variability. Even though these technologies have been reported to improve the quality of cleavage stage embryo evaluation during fresh culture, possible advantages in the evaluation of cryopreserved embryos have been scarcely explored. This study aims to compare morphometric and morphokinetic parameters between slow frozen and vitrified embryos and to determine their relationship to embryo survival and implantation rate (IR) after thawing/warming.

METHODS

During fresh culture, morphometric characteristics (Total Cell Volume (TCV), symmetry, fragmentation and number of blastomeres) were measured in 286 thawed/warmed embryos. Likewise, after thawing/warming, similar morphometric characteristics were measured in 135 survived embryos. Moreover, morphokinetic parameters (time to mitosis resumption and time to compaction) were measured in 90 embryos after thawing/warming. Then, using linear regression, we investigated the differences between vitrified and slow frozen embryos and the relation of the measured characteristics to embryo survival and IR. Statistical corrections were applied to account for data clustering and for multiple testing.

RESULTS

Vitrified embryos resume mitosis and start compaction significantly earlier than slow frozen embryos. Mitosis resumption rate was 82% for vitrified and 63% for slow frozen embryos and median time to mitosis resumption was 7.6 h and 13.1 h (p = 0.02), respectively. Compaction rate was 62% in vitrified and only 23% in slow frozen embryos. Median time to compaction was 18.1 h for vitrified embryos but, for slow frozen could not be computed since less than half of the slow frozen embryos reached compaction (p = 0.0001). Moreover, intact embryos resume mitosis significantly earlier than not intact ones regardless of the freezing method (rate: 79% vs. 66%, median time: 7.6 h vs 14.6 h, respectively, p = 0.03). Regarding morphometrics, slow frozen embryos showed lower TCV and higher blastomere symmetry after thawing than vitrified embryos despite having similar blastomere number. IR was related to blastomere number at cryopreservation in slow frozen embryos, but not in vitrified ones.

CONCLUSIONS

Interestingly, vitrified/warmed embryos undergo mitosis resumption and compaction significantly earlier than slow frozen/thawed embryos. However, the clinical use of this morphokinetic parameters still remains to be investigated in larger studies.

TRIAL REGISTRATION

Retrospectively registered on December 15, 2015 NCT02639715 .

Prognostic factors for patients undergoing vitrified-warmed human embryo transfer cycles: a retrospective cohort study

We examined the prognostic factors for pregnancy in 210 vitrified-warmed embryo transfer (ET) cycles in 121 patients. The univariate analysis showed that age, gravida, the number of cycles associated with infertility caused by endometriosis, the number of previous assisted reproductive technology (ART) treatment cycles, and the number of ICSI procedures were significantly lower in pregnant cycles compared with non-pregnant cycles. The percentages of ET using at least one intact embryo and of ET using at least one embryo that had developed further after warming were significantly higher in pregnant cycles compared with non-pregnant cycles. Multivariate logistic regression analysis showed that previous ART treatment cycles, ET with at least one intact embryo, and ET using at least one embryo that had developed further were independent prognostic factors for pregnancy in vitrified-warmed ET cycles. We conclude that fewer previous ART treatment cycles, ET using at least one intact embryo, and ET with embryos that have developed further after warming might be favourable prognostic factors for pregnancy in vitrified-warmed ET cycles.

Effect of embryo morphology and morphometrics on implantation of vitrified day 3 embryos after warming: a retrospective cohort study

BACKGROUND

Characteristics routinely used to evaluate embryo quality after thawing include number of blastomeres survived and presence of mitosis resumption after overnight culture. It is unknown to which extent symmetry and fragmentation affect implantation after warming and whether application of stricter criteria either before vitrification or after warming would improve implantation rate (IR) of vitrified/warmed embryos. This study aimed to find new parameters to improve selection criteria for vitrification and for transfer after warming.

METHODS

Firstly, we evaluated standard morphological characteristics (intact survival, mitosis resumption, number of blastomeres, symmetry and fragmentation) of 986 warmed day 3 embryos and, from a subset of 654, we evaluated morphometric characteristics (fragmentation, symmetry and volume change). Secondly, we tested the hypothesis that IR of day 3 vitrified/warmed embryos is influenced by morphometric characteristics. IR per embryo transferred was calculated using embryos that were transferred in a single embryo transfer (SET) or a double embryo transfer (DET) with either 0 or 100 % implantation (830/986). We investigated the significant differences in IR between the different categories of a specific characteristic. These categories were based on our standard embryo evaluation system. The statistical tests Chi-square, Fisher's exact or Cochrane-Armitage were used according to the type and/or categories of the variable.

RESULTS

The 986 embryos were transferred in 671 FET cycles with 16.9 % (167/986) IR. After exclusion of DET with 1 embryo implanted, IR per embryo transferred was 12.4 % (103/830). Embryo symmetry, fragmentation and volume change in vitrified/warmed day 3 embryos were not associated with IR. However, when mitosis resumption was present after overnight culture, intact embryos reached significantly higher IR than non-intact embryos and only when the embryo compacted after overnight culture the number of cells damaged after warming had no effect on IR. Concretely, embryos with 8 cells after warming or >9 cells after overnight culture-including compacted embryos-reached the highest IR (>15 %) while embryos with <6 cells after warming or with ≤6 cells after overnight culture had extremely low IR (<1 %).

CONCLUSIONS

IR of vitrified embryos is determined by the number of cells lost, by the occurrence of mitosis resumption, and by the specific number of blastomeres present but not by fragmentation, blastomere symmetry or volume change. Unselecting embryos for cryopreservation because of fragmentation >10 % and/or symmetry < 75 % only leads to unwanted loss of embryos with acceptable implantation potential.

TRIAL REGISTRATION

Retrospectively registered NCT02639715 .

Pregnancy outcomes of blastocysts cultured overnight after thawing

PURPOSE

To compare embryo quality and outcomes of blastocysts thawed and transferred the same day with those thawed and cultured overnight before transfer.

METHODS

In this retrospective study, patients with infertility who underwent thawed embryo transfer (TET) the same day as thawing (0TET group) and those that received TET after embryos were thawed and cultured overnight before transfer (1TET group) were enrolled. Univariable and multivariable logistic regression were performed to detect the factors associated with the clinical pregnancy rate (CPR), implantation rate, miscarriage rate, and multiple pregnancy rate.

RESULTS

A total of 489 patients (489 cycles) were included with 234 in the 0TET group and 255 in the 1TET group. There were no significant differences between the two groups with respect to age, body mass index (BMI), basal FSH and estradiol (E2) level, and causes of infertility (all, p > 0.05). There were no significant differences in the CPR, implantation rate, miscarriage rate, or multiple pregnancy rate between the two groups (all, p > 0.05), and this finding was irrespective of the endometrial preparation method.

CONCLUSIONS

Pregnancy outcomes are the same for blastocysts thawed and cultured overnight 1 day before transfer and those thawed and transferred on the same day.

Perinatal outcome in fresh versus frozen embryo transfer in ART cycles

BACKGROUND

Despite of higher pregnancy rate after frozen embryo transfer (FET) which is accepted by the majority of researches, the safety of this method and its effect on neonatal outcome is still under debate.

OBJECTIVE

The aim of this study was to evaluate pregnancy and neonatal outcome of FET compare to fresh cycles.

MATERIALS AND METHODS

In this study,1134 patients using fresh ET and 285 women underwent FET were investigated regarding live birth as primary outcome and gestational age, birth weight, gender, multiple status, ectopic pregnancy, still birth and pregnancy loss as secondary outcomes.

RESULTS

Our results showed that there is no difference between FET and fresh cycles regarding live birth (65.6% vs. 70.4% respectively). Ectopic pregnancy, still birth and abortion were similar in both groups. The mean gestational age was significantly lower among singletons in FET group compared to fresh cycles (p=0.047). Prematurity was significantly elevated among singleton infants in FET group (19.6%) in comparison to neonates born after fresh ET (12.8%) (p=0.037).

CONCLUSION

It seems that there is no major difference regarding perinatal outcome between fresh and frozen embryo transfer. Although, live birth is slightly increased in fresh cycles and prematurity was significantly increased among singleton infants in FET group.

Can repeated IVF-ICSI-cycles be avoided by using blastocysts developing from poor-quality cleavage stage embryos?

In many clinics, good-quality embryos are selected for embryo transfer and cryopreservation at the cleavage stage, and poor-quality embryos are discarded. The aim of this retrospective study was to examine how many repeated IVF cycles could be avoided by culturing the cleavage stage poor-quality embryos to blastocyst stage and transferring them after vitrification and warming (604 IVF and intracytoplasmic sperm injection [IVF-ICSI] cycles were included). Poor-quality cleavage stage embryos not eligible for transfer or cryopreservation were cultured until day 5 or 6, and those developing to the blastocyst stage were vitrified. The rate of vitrified blastocysts and clinical pregnancy and delivery rate of the warmed blastocysts was evaluated. The effect of the extended culture on the cumulative delivery rate, and the number of avoided new treatment cycles was calculated. The surplus blastocysts resulted in clinical pregnancy, spontaneous abortion and delivery rates of 24.6%, 27.3% and 17.2% respectively. The use of surplus blastocysts raised cumulative delivery rate from 43% to 47% and 53 repeated new cycles were avoided. This study shows that the cumulative delivery rate can be increased, and repeated IVF-ICSI treatments avoided by using blastocysts developing from poor-quality cleavage stage embryos, which otherwise would have been discarded.

Using the Society for Assisted Reproductive Technology Clinic Outcome System morphological measures to predict live birth after assisted reproductive technology

OBJECTIVE

To model morphological assessments of embryo quality that are predictive of live birth.

DESIGN

Longitudinal cohort using cycles reported in the Society for Assisted Reproductive Technology Clinic Outcomes Reporting System (SART CORS) between 2007 and 2011.

SETTING

Clinic-based data.

PATIENT(S)

Fresh autologous assisted reproductive technology (ART) cycles with ETs on day 3 or day 5 and morphological assessments reported (25,409 cycles with one embryo transferred and 96,093 cycles with two embryos transferred). Live-birth rates were modeled by morphological assessments using backward-stepping logistic regression for cycle 1 and over five cycles, separately for day 3 and day 5 transfers and number of embryos transferred (1 or 2). Additional models for each day of transfer also included the number of oocytes retrieved and the number of embryos cryopreserved.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Live births.

RESULT(S)

Morphological assessments of grade, stage, fragmentation, and symmetry were significant for the day 3 models; grade, stage, and trophectoderm were significant in the day 5 model; inner-cell mass was significant in the models when two embryos were transferred. Number of oocytes retrieved and number of embryos cryopreserved were significant for both day 3 and day 5 models.

CONCLUSION(S)

These findings confirm the significant association between embryo quality parameters reported to SART CORS and live-birth rate after ART.

Preimplantation embryo metabolism and culture systems: experience from domestic animals and clinical implications

Despite advantages of in vitro embryo production in many species, widespread use of this technology is limited by generally lower developmental competence of in vitro derived embryos compared to in vivo counterparts. Regardless, in vivo or in vitro gametes and embryos face and must adjust to multiple microenvironments especially at preimplantation stages. Moreover, the embryo has to be able to further adapt to environmental cues in utero to result in the birth of live and healthy offspring. Enormous strides have been made in understanding and meeting stage-specific requirements of preimplantation embryos, but interpretation of the data is made difficult due to the complexity of the wide array of culture systems and the remarkable plasticity of developing embryos that seem able to develop under a variety of conditions. Nevertheless, a primary objective remains meeting, as closely as possible, the preimplantation embryo requirements as provided in vivo. In general, oocytes and embryos develop more satisfactorily when cultured in groups. However, optimization of individual culture of oocytes and embryos is an important goal and area of intensive current research for both animal and human clinical application. Successful culture of individual embryos is of primary importance in order to avoid ovarian superstimulation and the associated physiological and psychological disadvantages for patients. This review emphasizes stage specific shifts in embryo metabolism and requirements and research to optimize in vitro embryo culture conditions and supplementation, with a view to optimizing embryo culture in general, and culture of single embryos in particular.

The influence of patient and cohort parameters on the incidence and developmental potential of embryos with poor quality traits for use in human embryonic stem cell derivation

BACKGROUND

Human embryonic stem cells (hESCs) are most commonly derived from the inner cell mass (ICM) of blastocyst stage embryos. While the majority of hESC lines originate from good-quality embryos donated after cryogenic storage, poor-quality embryos (PQEs) not suitable for clinical use have also been shown to generate hESC. This provides a newfound function for embryos that would otherwise be discarded following IVF or ICSI. Owing to their lack of clinical importance, however, data on the poorest embryos in a cohort go largely unreported in the literature. It is therefore of interest to better understand the availability of PQEs from IVF/ICSI cycles and to determine their ability to develop into blastocysts with good-quality ICMs for use in hESC derivation. In this study, we investigate the influence of patient parameters and embryo cohort on PQE incidence, blastocyst development, ICM quality and successful hESC derivation from donated PQEs.

METHODS

PQEs from 736 patient cycles that did not meet our clinical criteria for transfer or cryopreservation were cultured until Day 6 of development and assessed for blastocyst formation and ICM quality. A subset of blastocysts with good-quality ICMs were then used for hESC derivation attempts. Anonymous patient data such as maternal age, embryo history and cohort parameters were then retrospectively compiled and analysed.

RESULTS

PQEs made up 46.8% of two pronucleate embryos created from IVF/ICSI. Including embryos with abnormal fertilization, a mean of 3.6 ± 2.8 embryos were donated per cycle with 32.6% developing to the blastocyst stage. Good-quality ICM were produced in 13.9% of PQEs cultured. Of good-quality ICM, 15.4% of those used in hESC derivation attempts resulted in a novel line. The PQEs that originated from older patients (>37 year) or from cycles that did not result in pregnancy had significantly diminished blastocyst development and ICM quality. Maternal age was also shown to further influence the ability of good-quality ICMs to generate hESC.

CONCLUSIONS

PQEs are an abundant source of embryos capable of developing to blastocysts with good-quality ICMs and subsequently generating novel hESC. We have shown that prognostic variables used to predict IVF/ICSI outcome can also help predict which PQEs have the best hESC developmental potential. Owing to the diversity of PQE origin, experiments designed to compare hESC derivation techniques or efficiency using PQEs should consider clinical IVF/ICSI parameters to establish groups with equal developmental competence. Additional investigation is needed to determine if these results are applicable to hESC derivation using good-quality embryos.