Blastocyst culture using single versus sequential media in clinical IVF: a systematic review and meta-analysis of randomized controlled trials

The impact of implementing a non-invasive preimplantation genetic testing for aneuploidies (niPGT-A) embryo culture protocol on embryo viability and clinical outcomes

STUDY QUESTION

Are modifications in the embryo culture protocol needed to perform non-invasive preimplantation genetic testing for aneuploidies (niPGT-A) affecting clinical reproductive outcomes, including blastocyst development and pregnancy outcomes?

SUMMARY ANSWER

The implementation of an embryo culture protocol to accommodate niPGT-A has no impact on blastocyst viability or pregnancy outcomes.

WHAT IS KNOWN ALREADY

The recent identification of embryo cell-free (cf) DNA in spent blastocyst media has created the possibility of simplifying PGT-A. Concerns, however, have arisen at two levels. First, the representativeness of that cfDNA to the real ploidy status of the embryo. Second, the logistical changes that need to be implemented by the IVF laboratory when performing niPGT-A and their effect on reproductive outcomes. Concordance rates of niPGT-A to invasive PGT-A have gradually improved; however, the impact of culture protocol changes is not as well understood.

STUDY DESIGN, SIZE, DURATION

As part of a trial examining concordance rates of niPGT-A versus invasive PGT-A, the IVF clinics implemented a specific niPGT-A embryo culture protocol. Briefly, this involved initial culture of fertilized oocytes following each laboratory standard routine up to Day 4. On Day 4, embryos were washed and cultured individually in 10 μl of fresh media. On Day 6 or 7, blastocysts were then biopsied, vitrified, and media collected for the niPGT-A analysis. Six IVF clinics from the previously mentioned trial were enrolled in this analysis. In the concordance trial, Clinic A cultured all embryos (97 cycles and 355 embryos) up to Day 6 or 7, whereas in the remaining clinics (B-F) (379 cycles), nearly a quarter of all the blastocysts (231/985: 23.5%) were biopsied on Day 5, with the remaining blastocysts following the niPGT-A protocol (754/985: 76.5%). During the same period (April 2018-December 2020), the IVF clinics also performed standard invasive PGT-A, which involved culture of embryos up to Days 5, 6, or 7 when blastocysts were biopsied and vitrified.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In total, 428 (476 cycles) patients were in the niPGT-A study group. Embryos from 1392 patients underwent the standard PGT-A culture protocol and formed the control group. Clinical information was obtained and analyzed from all the patients. Statistical comparisons were performed between the study and the control groups according to the day of biopsy.

MAIN RESULTS AND THE ROLE OF CHANCE

The mean age, number of oocytes, fertilization rates, and number of blastocysts biopsied were not significantly different for the study and the control group. Regarding the overall pregnancy outcomes, no significant effect was observed on clinical pregnancy rate, miscarriage rate, or ongoing pregnancy rate (≥12 weeks) in the study group compared to the control group when stratified by day of biopsy.

LIMITATIONS, REASONS FOR CAUTION

The limitations are intrinsic to the retrospective nature of the study, and to the fact that the study was conducted in invasive PGT-A patients and not specifically using niPGT-A cases.

WIDER IMPLICATIONS OF THE FINDINGS

This study shows that modifying current IVF laboratory protocols to adopt niPGT-A has no impact on the number of blastocysts available for transfer and overall clinical outcomes of transferred embryos. Whether removal of the invasive biopsy step leads to further improvements in pregnancy rates awaits further studies.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by Igenomix. C.R., L.N.-S., and D.V. are employees of Igenomix. D.S. was on the Scientific Advisory Board of Igenomix during the study.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov (NCT03520933).

Does cleavage- versus blastocyst-stage embryo transfer improve fertility rates in women over 38 years of age undergoing assisted reproductive technology?

OBJECTIVE

To evaluate whether extending embryo culture to day 5 (D5) affects pregnancy rates in women older than 38 years undergoing in vitro fertilization (IVF).

METHODS

This retrospective, observational cohort study included data from fresh IVF cycles of women over 38 years, during 2011-2021. The cohort was divided according to day 3 (D3) versus D5 embryo transfer (ET).

RESULTS

A total of 346 patients (ages 38-45 years) who underwent 496 IVF cycles were included, each yielding one to six embryos. A total of 374 (75%) fresh D3 ETs were compared with 122 (25%) D5 ETs. Demographically, there were more nulliparas in the D3 group (189 [50.9%] vs 47 [38.8%], P = 0.021). Higher gonadotropin dosage was used (3512 ± 1346 vs 3233 ± 1212 IU, P = 0.045) and lower maximum estradiol levels were reached in the D3 group (1129 ± 685 vs 1432 ± 708 pg/mL, P = 0.002). Thirty-three (27%) of the D5 cycles resulted in transfer cancelation due to failure of blastocyst formation (P = 0.001). However, clinical pregnancy rates (P = 0.958), live birth rates (P = 0.988), and miscarriage rates (P = 0.710) did not differ between D3 and D5 ETs. Multivariable logistic regression for clinical pregnancy rate showed that day of transfer did not have a significant effect on the odds (P = 0.376), but maternal age (P = 0.001) and number of retrieved oocytes (P = 0.009) were significant variables.

CONCLUSIONS

In older women, culturing embryos to blastocyst stage can decrease invalid ETs without reducing pregnancy rates. Cancelation rates are higher but it may avoid interventions and conserve valuable time.

To Assess or Not to Assess: Reconsidering Day 3 Embryo Quality in Planned Freeze-All Blastocyst Cycles

Day 3 embryo quality is a predictor of in vitro fertilization (IVF) success rates in cleavage-stage embryo transfer. However, the association between day 3 embryo quality and clinical outcomes in blastocyst transfer policy is largely unknown. This retrospective study included 1074 frozen-thawed single day 5/6 blastocyst transfers between January 2019 and December 2022. Three groups were assessed depending on whether the transferred blastocyst derived from a top-quality, good-quality, or poor-quality embryo at day 3. The analysis was conducted independently for each blastocyst quality group (top, good, and poor) using multivariable logistic regression. We applied a Factorial Analysis of Mixed Data (FAMD) to reduce the potential collinearity between the covariates used in the model. All the blastocysts included in this study were obtained from the first ICSI freeze-all cycles. The cleavage and blastocysts stages were assessed between 67 ± 0.5 (day 3), 115 ± 0.5 (day 5), and 139 ± 0.5 (day 6) hours post-insemination (hpi), respectively. After adjusting for the day of transfer (day 5 or day 6) and FAMD dimensions, no statistical differences in a β-HCG, clinical pregnancy, and live birth were observed among the same-quality blastocysts derived from different day 3 embryo quality groups (top = A, good = B, and poor = C). Our findings showed that a day 3 embryo quality assessment may be unnecessary in planned freeze-all blastocyst cycles.

In Vitro Culture of Mammalian Embryos: Is There Room for Improvement?

Preimplantation embryo culture, pivotal in assisted reproductive technology (ART), has lagged in innovation compared to embryo selection advancements. This review examines the persisting gap between in vivo and in vitro embryo development, emphasizing the need for improved culture conditions. While in humans this gap is hardly estimated, animal models, particularly bovines, reveal clear disparities in developmental competence, cryotolerance, pregnancy and live birth rates between in vitro-produced (IVP) and in vivo-derived (IVD) embryos. Molecular analyses unveil distinct differences in morphology, metabolism, and genomic stability, underscoring the need for refining culture conditions for better ART outcomes. To this end, a deeper comprehension of oviduct physiology and embryo transport is crucial for grasping embryo-maternal interactions' mechanisms. Research on autocrine and paracrine factors, and extracellular vesicles in embryo-maternal tract interactions, elucidates vital communication networks for successful implantation and pregnancy. In vitro, confinement, and embryo density are key factors to boost embryo development. Advanced dynamic culture systems mimicking fluid mechanical stimulation in the oviduct, through vibration, tilting, and microfluidic methods, and the use of innovative softer substrates, hold promise for optimizing in vitro embryo development.

Preimplantation genetic testing for aneuploidy: predictive embryonic factors

PURPOSE

In a preimplantation genetic testing for aneuploidy (PGT-A) cycle, does the blastocyst quality before biopsy, or the day of biopsy, or the embryo hatching status have an impact on either euploidy or the rate of embryo survival after freezing?

METHODS

This was a retrospective study including 6130 biopsied blastocysts coming from 1849 PGT-A cycles performed in our center (2016-2022). Embryos were categorized according to the inner cell mass and trophectoderm quality, using Gardner's scoring (excellent: AA; good: AB, BA, BB; poor: AC, CA, BC, CB, CC); the day of biopsy (5 or 6); and their hatching status (fully hatched blastocysts [FHB] or non-fully hatched blastocysts [nFHB]). The independent relationship between each group and both euploidy and survival rate was assessed.

RESULTS

Excellent-quality embryos were more euploid than both good- and poor-quality embryos (52.69%, 39.69%, and 26.21%; p < 0.001), and day 5-biopsied embryos were more euploid than day 6-biopsied embryos (39.98% and 34.80%; p < 0.001). Survival rates of excellent-quality (92.26%) and good-quality (92.47%) embryos were higher than survival rates in the poor-quality group (84.61%) (p = 0.011 and p = 0.002). Day 5-biopsied embryos survived better than day 6-biopsied embryos (93.71% vs. 83.69%; p < 0.001) and FHB had poorer survival than nFHB (78.61% vs. 93.52%; p < 0.001).

CONCLUSIONS

Excellent-quality and day 5-biopsied embryos are more prone to be euploid than good and poor or day 6-biopsied embryos, respectively. Poor-quality, day 6-biopsied embryos, and FHB have significantly lower survival after biopsy and vitrification.

Do IVF culture conditions have an impact on neonatal outcomes? A systematic review and meta-analysis

PURPOSE

Are embryo culture conditions, including type of incubator, oxygen tension, and culture media, associated with obstetric or neonatal complications following in vitro fertilization (IVF)?

METHODS

A systematic search of MEDLINE, EMBASE, and Cochrane Library was performed from January 01, 2008, until October 31, 2021. The studies reporting quantitative data on at least one of the primary outcomes (birthweight and preterm birth) for the exposure group and the control group were included. For oxygen tension, independent meta-analysis was performed using Review Manager, comparing hypoxia/normoxia. For culture media, a network meta-analysis was carried out using R software, allowing the inclusion of articles comparing two or more culture media.

RESULTS

After reviewing 182 records, 39 full-text articles were assessed for eligibility. A total of 28 studies were kept for review. Meta-analysis about the impact of incubator type on perinatal outcomes could not be carried out because of a limited number of studies. For oxygen tension, three studies were included. The pairwise meta-analysis comparing hypoxia/normoxia did not show any statistical difference for birthweight and gestational age at birth. For culture media, 18 studies were included. The network meta-analysis failed to reveal any significant impact of different culture media on birthweight or preterm birth.

CONCLUSION

No difference was observed for neonatal outcomes according to the embryo culture conditions evaluated in this review. Further research is needed about the safety of IVF culture conditions as far as future children's health is concerned.

Mammalian embryo culture media: now and into the future

For over 70years, since the culture of the first mammalian embryo in vitro , scientists have undertaken studies to devise and optimise media to support the manipulation and culture of gametes and embryos. This area of research became especially active in the late 1970s onwards following the successful birth of the first human in vitro fertilised embryo. This review summarises some of the key advances in mammalian embryo culture media over time based on a greater understanding of the biochemical milieu of the reproductive tract. It highlights how learnings from studies in mice and agricultural species have informed human culture media compositions, in particular the inclusion of albumin, growth factors, cytokines, and antioxidants into contemporary culture media formulations, and how these advances may then in turn help to inform and guide development of in vitro culture systems used in other arenas, in particular agriculture. Additionally, it will highlight how the introduction of new technologies, such as timelapse, can influence current trends in media composition and usage that may see a return to a single step medium.

Embryo Culture Medium Has No Impact on Mosaicism Rates: a Sibling Oocyte Study

Human embryos cultured in vitro can contain two or more cytogenetically distinct cell lineages known as "chromosomal mosaicism". Since mosaicism is produced by mitotic errors after fertilization occurs, culture conditions might contribute to mosaicism origins. Many studies demonstrated that euploidy rates are not affected by culture media; however, whether oocytes cultured under continuous culture media (CCM) or sequential culture media (SCM) has a higher risk of mosaicism occurring remains unsolved. Therefore, this study aims to determine whether mosaicism rates differ when sibling oocytes are cultured in CCM or SCM. A single center observational study was performed including 6072 sibling oocytes. Mature oocytes (MII) were inseminated and cultured in CCM (n = 3,194) or SCM (n = 2,359) until blastocyst stage for trophectoderm (TE) biopsy on day (D) 5, D6, or D7 for preimplantation genetic testing analysis with a semi-automated next-generation sequencing. Mosaicism was classified as low (30-50%) or high (50-80%) based on the percentage of abnormal cells constitution detected in TE samples. As a result, 426 women with a mean age of 34.7 ± 6.4 years were included in the study. Fertilization rates were comparable between CCM and SCM (74.0% vs 72.0%, p = 0.091). Although total blastulation rate and usable blastocyst rate (biopsied blastocysts) were significantly higher in CCM than SCM (75.3 % vs. 70.3%, p < 0.001 and 58.0% vs. 54.5%, p = 0.026), euploidy rates did not differ significantly (45.2% vs. 45.7%, p = 0.810, respectively). Mosaicism rate was not significantly different for blastocysts cultured in CCM or SCM (4.7% vs. 5.1%, p = 0.650), neither the proportion of low or high mosaic rates (3.7% vs. 4.4%, p = 0.353 and 1.0% vs. 0.7%, p = 0.355, respectively). Hence, it was concluded that CCM or SCM does not have an impact on mosaicism rate of embryos cultured until the blastocyst stage.

Meiotic and mitotic aneuploidies drive arrest of in vitro fertilized human preimplantation embryos

BACKGROUND

The high incidence of aneuploidy in early human development, arising either from errors in meiosis or postzygotic mitosis, is the primary cause of pregnancy loss, miscarriage, and stillbirth following natural conception as well as in vitro fertilization (IVF). Preimplantation genetic testing for aneuploidy (PGT-A) has confirmed the prevalence of meiotic and mitotic aneuploidies among blastocyst-stage IVF embryos that are candidates for transfer. However, only about half of normally fertilized embryos develop to the blastocyst stage in vitro, while the others arrest at cleavage to late morula or early blastocyst stages.

METHODS

To achieve a more complete view of the impacts of aneuploidy, we applied low-coverage sequencing-based PGT-A to a large series (n = 909) of arrested embryos and trophectoderm biopsies. We then correlated observed aneuploidies with abnormalities of the first two cleavage divisions using time-lapse imaging (n = 843).

RESULTS

The combined incidence of meiotic and mitotic aneuploidies was strongly associated with blastocyst morphological grading, with the proportion ranging from 20 to 90% for the highest to lowest grades, respectively. In contrast, the incidence of aneuploidy among arrested embryos was exceptionally high (94%), dominated by mitotic aneuploidies affecting multiple chromosomes. In turn, these mitotic aneuploidies were strongly associated with abnormal cleavage divisions, such that 51% of abnormally dividing embryos possessed mitotic aneuploidies compared to only 23% of normally dividing embryos.

CONCLUSIONS

We conclude that the combination of meiotic and mitotic aneuploidies drives arrest of human embryos in vitro, as development increasingly relies on embryonic gene expression at the blastocyst stage.

Making and selecting the best embryo in the laboratory

Over the past 4 decades our ability to maintain a viable human embryo in vitro has improved dramatically, leading to higher implantation rates. This has led to a notable shift to single blastocyst transfer and the ensuing elimination of high order multiple gestations. Future improvements to embryo culture systems will not only come from new improved innovative media formulations (such as the inclusion of antioxidants), but plausibly by moving away from static culture to more dynamic perfusion-based systems now made a reality owing to the breakthroughs in three-dimensional printing technology and micro fabrication. Such an approach has already made it feasible to create high resolution devices for intracytoplasmic sperm injection, culture, and cryopreservation, paving the way not only for improvements in outcomes but also automation of assisted reproductive technology. Although improvements in culture systems can lead to further increases in pregnancy outcomes, the ability to quantitate biomarkers of embryo health and viability will reduce time to pregnancy and decrease pregnancy loss. Currently artificial intelligence is being used to assess embryo development through image analysis, but we predict its power will be realized through the creation of selection algorithms based on the integration of information related to metabolic functions, cell-free DNA, and morphokinetics, thereby using vast amounts of different data types obtained for each embryo to predict outcomes. All of this will not only make assisted reproductive technology more effective, but it will also make it more cost effective, thereby increasing patient access to infertility treatment worldwide.

Obstetric and perinatal outcomes after embryos cultured in one-step versus sequential culture media systems in vitrified-warmed single blastocyst transfer cycles

RESEARCH QUESTION

Does type of culture medium used influence obstetric and perinatal outcomes after vitrified-warmed single blastocyst transfers?

DESIGN

Retrospective cohort study involving singletons after vitrified-warmed single blastocyst embryo transfers, using embryos cultured in either Irvine Continuous Single Culture medium (CSC) or Vitrolife G5TM PLUS medium culture system between 2013 and 2020.

RESULTS

A total of 2475 women who had singleton deliveries were included for final analysis: 1478 had embryos cultured in CSC and 997 had embryos cultured in G5TM PLUS medium. Birth outcomes, including preterm birth, mean birth weight, gestational age- and sex-adjusted birth weight (Z-scores), rates of large-for-gestational-age, small-for-gestational-age, low birth weight and macrosomia, and the distribution of newborn gender did not differ significantly between groups in crude and adjusted analyses. Women whose embryos were cultured in G5TM PLUS frequently suffered from pregnancy-induced hypertensive disorders compared with those who had embryos cultured in CSC (4.7% versus 3.0%; P = 0.031). This difference was no longer significant after adjusting for several key confounders (adjusted odds ratio 1.49, 95% CI 0.94 to 2.38, P = 0.087). Other obstetric complications, including gestational diabetes mellitus, preterm premature rupture of membranes, abnormal placentation, postpartum haemorrhage and the mode of delivery were all similar between the two groups.

CONCLUSIONS

The present study adds new information to the current evidence by suggesting that the embryo culture medium does not affect birth outcomes and obstetric complications when comparison is limited to Irvine CSC and Vitrolife G5TM PLUS in vitrified-warmed single blastocyst transfer cycles.

Does PGT-A improve assisted reproduction treatment success rates: what can the UK Register data tell us?

PURPOSE

To show how naïve analyses of aggregated UK ART Register data held by the Human Fertilisation and Embryology Authority to estimate the effects of PGT-A can be severely misleading and to indicate how it may be possible to do a more credible analysis. Given the limitations of the Register, we consider the extent to which such an analysis has the potential to answer questions about the real-world effectiveness of PGT-A.

METHODS

We utilise the publicly available Register datasets and construct logistic regression models for live birth events (LBE) which adjust for confounding. We compare all PGT-A cycles to control groups of cycles that could have had PGT-A, excluding cycles that did not progress to having embryos for biopsy.

RESULTS

The primary model gives an odds ratio for LBE of 0.82 (95% CI 0.68-1.00) suggesting PGT-A may be detrimental rather than beneficial. However, due to limitations in the availability of important variables in the public dataset, this cannot be considered a definitive estimate. We outline the steps required to enable a credible analysis of the Register data.

CONCLUSION

If we compare like with like groups, we obtain estimates of the effect of PGT-A that suggest an overall modest reduction in treatment success rates. These are in direct contrast to an invalid comparison of crude success rates. A detailed analysis of a fuller dataset is warranted, but it remains to be demonstrated whether the UK Register data can provide useful estimates of the impact of PGT-A when used as a treatment add-on.

Strategy for embryo transfer to improve pregnancy outcomes in advanced maternal age

The purpose of this retrospective study was to optimize the transplantation strategy for women of advanced maternal age to achieve live births within the shortest time. Data were collected from patients older than 40 years who underwent assisted reproductive therapy at our centre from 1 January 2009 to 31 December 2019. In total, 1023 cases of fresh cleavage embryo transfer (CET) cycles, 280 cases of frozen-thawed blastocyst transfer (FBT) cycles, and 26 cases of frozen-thawed CET (FCET) cycles were included. The main outcome was the live birth rate (LBR). The secondary outcomes were the clinical pregnancy rate (CPR) and neonatal outcomes. Multivariable logistic regression was performed to adjust for confounding factors. The blastocyst formation rate of patients older than 40 years was 23.5%, the freezing cycle rate was 19.8%, and the fresh-embryo transfer rate was 83.0%. The implantation rate, CPR, and LBR were significantly different among the CET, FCET, and FBT groups. There were no significant differences in multiple pregnancies and abortion rates among the groups, and neonatal outcomes were similar. Multivariate logistic regression analysis showed that, compared with the CET group, LBR did not increase in the FCET group, whereas LBR increased in the FBT group. For patients older than 40 years when having approximately eight embryos after fertilization, blastocyst transfer can be considered after fully discussing the advantages and disadvantages of blastocyst culture. Alternatively, CET can be performed first, followed by FBT if the cleavage embryo transfer is unsuccessful.

Significance of the association between early embryonic development and endocytosis

Fertilization triggers a process called maternal-to-zygotic transition, in which the oocyte undergoes oocyte-to-embryo transition, leading to massive intracellular remodeling toward early embryogenesis. This transition requires the degradation of oocyte-derived components; however, the significance and mechanism of degradation of cell surface components remain unknown. In this review, we focused on the dynamics of plasma membrane proteins and investigated the relationship between embryonic development and endocytosis. Our survey of the extant literature on the topic led to the conclusion that clathrin-mediated endocytosis is essential for the progression of early embryogenesis and selective degradation of oocyte-derived plasma membrane proteins in mouse embryos, as reported by studies analyzing maternal cellular surface proteins, including a glycine transporter, GlyT1a. Evaluation of such endocytic activity in individual embryos may allow the selection of embryos with higher viability in assisted reproductive technologies, and it is important to select viable embryos to increase the rates of successful pregnancy and live birth. Although the early embryonic developmental abnormalities are mainly accompanied with chromosomal aneuploidy, other causes and mechanisms remain unclear. This review summarizes molecular biological approaches to early embryonic developmental abnormalities and their future prospects.

cd26 Knockdown Negatively Affects Porcine Parthenogenetic Preimplantation Embryo Development

cd26 is ubiquitously distributed in the body, particularly in the endothelial and epithelial cells, with the highest expression in the kidney, liver, and small intestine. In humans, cd26 serves as a marker for the embryo implantation phase. However, little is known about the role of cd26 in porcine pre-implantation embryo development. Here, we aimed to examine siRNA-induced cd26 downregulation in the cytoplasm of MII oocytes, to determine whether cd26 is involved in the regulation of porcine pre-implantation embryonic development. The cd26 siRNA was micro-injected into the cytoplasm of MII oocytes, which were then parthenogenetically activated electrically in a medium containing 0.3M Mannitol. Inhibition of the cd26 expression did not affect cleavage but stopped development in the blastocyst stage. Additionally, the cd26 siRNA-treated blastocysts had significantly more apoptotic cells than the untreated blastocysts. Among the 579 transcripts evaluated with transcriptome resequencing, 38 genes were differentially expressed between the treatment and control blastocysts (p < 0.05). Twenty-four genes were upregulated in cd26 siRNA-injected blastocysts, whereas 14 were downregulated. These genes are involved in apoptosis, accumulation of reactive oxygen species, and aberrant expression of ribosomal protein genes. Our results indicate that cd26 is required for proper porcine parthenogenetic activation during embryonic development.

Development of a dynamic machine learning algorithm to predict clinical pregnancy and live birth rate with embryo morphokinetics

Objective

Design

Setting

Patient(s)

Intervention(s)

Main Outcome Measure(s)

Result(s)

Conclusion(s)

The Impact of Culture Medium on Morphokinetics of Cleavage Stage Embryos: An Observational Study

To study the impact of culture media on preimplantation morphokinetics used for predicting clinical outcomes. All IVF and ICSI cycles performed between 2012 and 2017 with time-lapse information available were included. In November 2014, culture medium was changed from Vitrolife G-1 PLUS to SAGE 1-Step. Each embryo was retrospectively assigned a morphokinetic-based KIDScore for prediction of implantation. Clinical outcomes were retrieved from medical records. Linear mixed models were used to study differences in morphokinetic parameters, a proportional odds model for KIDScore ranking and logistic regression for differences in clinical outcomes. All analyses were adjusted for patient and treatment characteristics. In 253 (63.1%) cycles, embryos (n = 671) were cultured in Vitrolife, and in 148 (36.9%) cycles, embryos (n = 517) were cultured in SAGE. All cleavage divisions occurred earlier for SAGE embryos than for Vitrolife embryos (2-cell: -2.28 (95%CI: -3.66, -0.89), 3-cell: -2.34 (95%CI: -4.00, -0.64), 4-cell: -2.41 (95%CI: -4.11, -0.71), 5-cell: -2.54 (95%CI: -4.90, -0.18), 6-cell: -3.58 (95%CI: -6.08, -1.08), 7-cell: -5.62 (95%CI: -8.80, -2.45) and 8-cell: -5.32 (95%CI: -9.21, -1.42) hours, respectively). Significantly more embryos cultured in SAGE classified for the highest KIDScore compared to embryos cultured in Vitrolife (p < 0.001). No differences were observed in clinical outcomes. Our results demonstrate an impact of culture medium on preimplantation embryo developmental kinetics, which affects classification within the KIDScore algorithm, while pregnancy outcomes were comparable between the groups. This study underscores the need to include the type of culture medium in the development of morphokinetic-based embryo selection tools.

The impact of single-step and sequential embryo culture systems on obstetric and perinatal outcomes in singleton pregnancies: the Massachusetts Outcomes Study of Assisted Reproductive Technology

OBJECTIVE

To compare the obstetric and perinatal outcomes of deliveries conceived with embryos from single-step vs. sequential culture media systems.

DESIGN

Historical cohort of Massachusetts vital records linked to assisted reproductive technology clinic data from the Society for Assisted Reproductive Technology Clinic Outcome Reporting System and laboratory embryology data from two large academic hospital fertility centers.

SETTING

Not applicable.

PATIENTS

Patients with singleton live birth deliveries between 2004 and 2017 conceived with autologous assisted reproductive technology cycles with fresh blastocyst transfer using either single-step (n = 1,058) or sequential (n = 474) culture media systems.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Associations of single-step vs. sequential culture with obstetric outcomes (mode of delivery, placental abnormalities, pregnancy-induced hypertension, and gestational diabetes) and perinatal outcomes (preterm birth, low birthweight, small-for-gestational-age, and large-for-gestational-age [LGA]) were assessed with multivariate logistic modeling, adjusted for maternal age, race/ethnicity, education, parity, insurance type, protein supplementation, oxygen concentration, fertilization method, and number of transferred embryos.

RESULTS

Compared with sequential culture, single-step culture was associated with increased odds of LGA (adjusted odds ratio 2.1, 95% confidence interval 1.04-4.22). There were no statistically significant differences between single-step and sequential culture media systems in the odds of placental abnormalities, pregnancy-induced hypertension, gestational diabetes, prematurity, small-for-gestational-age, or low birthweight.

CONCLUSIONS

Single-step culture is associated with increased odds of LGA, indicating that embryo culture media systems may affect perinatal outcomes.

Novel Synthetic oviductal fluid for Conventional Freezing 1 (SCF1) culture medium improves development and cryotolerance of in vitro produced Holstein embryos

In vitro produced (IVP) embryos hold great promise in the cattle industry; however, suboptimal in vitro culture conditions induce metabolic dysfunction, resulting in poor development and low cryotolerance of IVP embryos. This limits the use of IVP embryos in the cattle industry for embryo transfer and commercial scale-up. Previous studies have reported the use of individual metabolic regulators in culture media to improve blastocyst development rates and cryopreservation. In this study, we hypothesized that using a combination of select regulators, chosen for their unique synergistic potential, would alleviate metabolic dysfunction and improve the development of in vitro produced embryos to make them more closely resemble in vivo derived embryos. To test this, we first compared lipid content between Holstein and Jersey embryos produced in vivo and in vitro, and then systematically determined the combination of metabolic regulators that led to the greatest improvements in embryonic development, lipid content, mitochondrial polarity, and cryotolerance. We also tested different slow freezing techniques to further improve cryotolerance and finally validated our results via a clinical trial. Overall, we found that the use of multiple metabolic regulators in one culture media, which we refer to as Synthetic oviductal fluid for Conventional Freezing 1 (SCF1), and an optimized slow freezing technique resulted in improved pregnancy rates for frozen IVP embryos compared to embryos cultured in a synthetic oviductal fluid media. Additionally, there was no difference in pregnancy rate between frozen and fresh IVP embryos cultured in SCF1. This suggests that optimizing culture conditions and slow freezing technique can produce cryotolerance IVP and should allow further dissemination of this assisted reproductive technology.

An expert commentary on essential equipment, supplies and culture media in the ART laboratory

The ART laboratory is a complex system designed to sustain the fertilization, survival, and culture of the preimplantation embryo to the blastocyst stage. ART outcomes depend on numerous factors, among which are the equipment, supplies and culture media used. The number and type of incubators also may affect ART results. While large incubators may be more suitable for media equilibration, bench-top incubators may provide better embryo culture conditions in separate or smaller chambers and may be coupled with time-lapse systems that allow continuous embryo monitoring. Microscopes are essential for observation, assessment, and micromanipulation. Workstations provide a controlled environment for gamete and embryo handling and their quantity should be adjusted according to the number of ART cycles treated in order to provide a steady and efficient workflow. Continuous maintenance, quality control and monitoring of equipment is essential and quality control devices such as the thermometer, and pH-meter are necessary to maintain optimal culture conditions. Tracking, appropriate delivery and storage conditions, and quality control of all consumables is recommended so that the adequate quantity and quality is available for use. Embryo culture media have evolved: preimplantation embryos are cultured either by sequential media or single-step media that can be used for interrupted or uninterrupted culture. There is currently no sufficient evidence that any individual commercially-available culture system is better than others in terms of embryo viability. In this review, we aim to analyse the various parameters that should be taken into account when choosing the essential equipment, consumables and culture media systems that will create optimal culture conditions and provide the most effective patient treatment.

Embryo culture media differentially alter DNA methylating enzymes and global DNA methylation in embryos and oocytes

The effects of culture media on DNA methylation process, which is one of the epigenetic mechanisms, have not been clearly elucidated although it is known that in vitro culture conditions alter epigenetic mechanisms. This study was designed to address the question: does embryo culture media approach, sequential or single step, differentially affect DNA methylating enzymes and global DNA methylation. Mouse zygotes were cultured either in single step or sequential culture media until the blastocyst stage and in vivo developed blastocyst were utilized as control. Similarly, GV stage oocytes were in vitro matured either in single step or first step of sequential culture media. In vivo matured MII oocytes were used as control. The expression levels and cellular localization of Dnmt1 and 3a enzymes were analyzed by immunofluorescence and western blot analysis while global DNA methylation was evaluated by immunofluorescence. We found that signal intensities of Dnmt1 and Dnmt3a enzymes were significantly low in embryos or oocytes cultured in sequential media compared to single step media and control, which were comparable amongst themself. Similarly, global DNA methylation level in single step media and control groups was comparable but both was higher than the sequential media. This study demonstrated that composition of culture media may differentially affect DNA methylation levels in mouse embryos and oocytes. Since abnormal DNA methylation may cause aberrant oocyte or embryo development, we think that further studies are needed to test human embryos and oocyte, and to explain molecular mechanisms.

Back to the future: optimised microwell culture of individual human preimplantation stage embryos

Although in vitro culture of human embryos is a crucial step in assisted reproduction, the lack of focused research hampers worldwide standardisation and consistent outcomes. Only 1.2% of research papers published in five leading journals in human reproduction in 2019 focused on in vitro culture conditions, creating the impression that the optimisation process has approached its limits. On the other hand, in vitro culture of mammalian embryos is based on old principles, while there is no consensus on basic issues as density, time, medium change, gas atmosphere and small technical details including the way of drop preparation. This opinion paper aims to highlight and analyse the slow advancement in this field and stimulate research for simple and affordable solutions to meet the current requirements. A possible way for advancement is discussed in detail. Selection of embryos with the highest developmental competence requires individual culture and modification of the widely used "drop under oil" approach. Current use of three-dimensional surfaces instead of large flat bottoms is restricted to time-lapse systems, but these wells are designed for optical clarity, not for the needs of embryos. The size and shape of the original microwells (Well of the Well; WOW) offer a practical and straightforward solution to combine the benefits of communal and individual incubation and improve the overall quality of cultured embryos.

Effect of sequential versus single-step culture medium on IVF treatments, including embryo and clinical outcomes: a prospective randomized study

PURPOSE

Sequential media G5 series (Vitrolife) and single-step medium Continuous Single Culture Complete (CSC-C) (Irvine Scientific) are two different culture media. We want to examine difference between culturing effects of the two media.

METHODS

To compare the fertilization and early embryo development, a prospective randomized controlled trial with sibling oocytes in infertile patients, aged ≤ 45 years with ≥ 8 oocytes (226 cycles) was conducted. Each half of the retrieved oocytes from the same patient were randomly allocated to two culture media separately. The remaining fresh cycles were randomly assigned to two culture media during the same period (179 cycles). We compared the clinical outcomes based on the total fresh ET cycles in this periods, in which the transferred embryos were only from one culture medium.

RESULTS

Embryo outcomes: 226 cycles, included 176 IVF and 50 ICSI cycles, were analyzed, which correspond to 3518 inseminated or micro-injected oocytes. Clinical outcomes: 71 (CSC-C) and 71 (G5 series) fresh ET cycles were compared. There were no significant differences in clinical outcomes and general fertilization rate. However, the fertilization rate was superior in the CSC-C when compared with G5 in ICSI cycles (76.51% vs. 67.25%, P = 0.008). In addition, the compacted embryo development rate was significantly higher in CSC-C on day 3. The cycles that had compacted embryos on day 3 demonstrated better outcomes both in embryos as well as clinically.

CONCLUSIONS

CSC-C had higher fertilization rates than G5 series in ICSI cycles. In addition, the compaction rates of day 3 embryos were significantly higher in CSC-C.

Molecular Drivers of Developmental Arrest in the Human Preimplantation Embryo: A Systematic Review and Critical Analysis Leading to Mapping Future Research

Developmental arrest of the preimplantation embryo is a multifactorial condition, characterized by lack of cellular division for at least 24 hours, hindering the in vitro fertilization cycle outcome. This systematic review aims to present the molecular drivers of developmental arrest, focusing on embryonic and parental factors. A systematic search in PubMed/Medline, Embase and Cochrane-Central-Database was performed in January 2021. A total of 76 studies were included. The identified embryonic factors associated with arrest included gene variations, mitochondrial DNA copy number, methylation patterns, chromosomal abnormalities, metabolic profile and morphological features. Parental factors included, gene variation, protein expression levels and infertility etiology. A valuable conclusion emerging through critical analysis indicated that genetic origins of developmental arrest analyzed from the perspective of parental infertility etiology and the embryo itself, share common ground. This is a unique and long-overdue contribution to literature that for the first time presents an all-inclusive methodological report on the molecular drivers leading to preimplantation embryos’ arrested development. The variety and heterogeneity of developmental arrest drivers, along with their inevitable intertwining relationships does not allow for prioritization on the factors playing a more definitive role in arrested development. This systematic review provides the basis for further research in the field.

The influence of the type of embryo culture media on the outcome of IVF/ICSI cycles

OBJECTIVE

Embryo culture media are important factors in IVF, which can significantly influence clinical outcome of IVF/ICSI cycles. Despite this, it is still not completely clear which formulation is most optimal and whether sequential or continuous media should be favored.

MATERIALS AND METHODS

This study retrospectively analyzed the outcome of IVF/ICSI cycles with regard to different types of culture media used to culture embryos, namely sequential and two types of single step continuous embryo culture media.

RESULTS

If the data were combined for both types of single step continuous embryo culture media the only significant difference we observed was the proportion of poor quality embryos on day 3, which was significantly higher (16.9% vs. 22.5%; P = 0.017) in the sequential media. The pregnancy (55.1% vs. 40.5%; P = 0.113) and live birth rates (42.9% vs. 33.8%; P = 0.308) were lower in continuous media, although the difference was not statistically significant. Furthermore, the blastocyst rate (sequential vs. continuous; 47.4% vs. 47.3%; P = 1), and birthweight (3280 ± 630g vs. 3272 ± 575g; P = 0.96) did not significantly differ regardless of the medium used to culture embryos. Additional comparison of each type of continuous medium to sequential media revealed that the difference in the quality of cleavage stage embryos for combined data of both continuous culture media may be derived from the group of cycles were SAGE 1-Step was used to culture embryos.

CONCLUSION

These results therefore indicate that continuous media can be equivalent to sequential media and could help lower the workload in busy IVF labs without impairing the clinical results. Although, caution is needed because this study is limited by its retrospective design. To confirm the results, especially in terms of live birth rates and perinatal outcome, a prospective study is needed with a higher number of included couples.

Embryo Culture Media Influence on Live Birth Rate and Birthweight after IVF/ICSI: A Systematic Review Comparing Vitrolife G5 Media to Other Common Culture Media

Previous studies have indicated that culture media vary in efficiency and outcomes, such as live birth rate, birthweight and embryo quality. Does Vitrolife G5 series culture media result in higher live birth rates and birthweight compared to other common culture media? This study is a systematic review based on the PRISMA criteria. Relevant search terms, mesh terms (PubMed and Cochrane) and Emtree terms (Embase) were identified. We searched the literature using PubMed, Embase and Cochrane, on November 10, 2019. The inclusion criteria involved published articles in English comparing Vitrolife G5 to other common culture media. We included randomized controlled trials (RCTs) and cohort studies. The quality of the studies was assessed using the Cochrane Risk of Bias tool 2.0 and the Newcastle-Ottawa Scale. Primary outcomes were live birth rate and birthweight. Secondary outcomes were fertilization rate, implantation rate, biochemical pregnancy rate, clinical pregnancy rate, miscarriage rate, multiple pregnancies and congenital malformations. Of 187 articles screened, 11 studies fulfilled the inclusion criteria: Five RCTs and six retrospective cohort studies. Only one study reported live birth rate, showing a non-significantly higher live birth rate for Vitrolife G5 media. Birthweight had equivocal results with three of six studies, showing significantly lower (2)/higher (1) birthweights, whereas the others were non-significant. Overall, there were no significant differences concerning secondary outcomes. The results are equivocal, and we need more studies to evaluate culture media and their effect on short- and long-term health.

Proteomics based drug repositioning applied to improve in vitro fertilization implantation: an artificial intelligence model

Embryo implantation is one of the most inefficient steps in assisted reproduction, so the identifying drugs with a potential clinical application to improve it has a strong interest. This work applies artificial intelligence and systems biology-based mathematical modeling strategies to unveil potential treatments by computationally analyzing and integrating available molecular and clinical data from patients. The mathematical models of embryo implantation computationally generated here simulate the molecular networks underneath this biological process. Once generated, these models were analyzed in order to identify potential repositioned drugs (drugs already used for other indications) able to improve embryo implantation by modulating the molecular pathways involved. Interestingly, the repositioning analysis has identified drugs considering two endpoints: (1) drugs able to modulate the activity of proteins whose role in embryo implantation is already bibliographically acknowledged, and (2) drugs that modulate key proteins in embryo implantation previously predicted through a mechanistic analysis of the mathematical models. This second approach increases the scope open for examination and potential novelty of the repositioning strategy. As a result, a list of 23 drug candidates to improve embryo implantation after IVF was identified by the mathematical models. This list includes many of the compounds already tested for this purpose, which reinforces the predictive capacity of our approach, together with novel repositioned candidates (e.g., Infliximab, Polaprezinc, and Amrinone). In conclusion, the present study exploits existing molecular and clinical information to offer new hypotheses regarding molecular mechanisms in embryo implantation and therapeutic candidates to improve it. This information will be very useful to guide future research.Abbreviations: IVF: in vitro fertilization; EI: Embryo implantation; TPMS: Therapeutic Performance Mapping System; MM: mathematical models; ANN: Artificial Neuronal Networks; TNFα: tumour necrosis factor factor-alpha; HSPs: heat shock proteins; VEGF: vascular endothelial growth factor; PPARA: peroxisome proliferator activated receptor-α PXR: pregnane X receptor; TTR: transthyretin; BED: Biological Effectors Database; MLP: multilayer perceptron.

Individual culture leads to decreased blastocyst formation but does not affect pregnancy outcomes in the setting of a single, vitrified-warmed euploid blastocyst transfer

PURPOSE

To evaluate embryology and pregnancy outcomes following individual and group embryo culture in the setting of contemporary laboratory practices and freeze-all cycles.

METHODS

Patients underwent ovarian stimulation followed by intracytoplasmic sperm injection (ICSI). Embryos proceeded through individual culture and then underwent preimplantation genetic testing for aneuploidy (PGT-A) via trophectoderm biopsy. In a subsequent cycle, participants underwent single embryo transfer of a vitrified-warmed, euploid embryo. Outcomes were compared to controls undergoing group culture during the same time frame. The Mann-Whitney U test and logistic regression models were utilized.

RESULTS

Outcomes were assessed for 144 patients whose embryos underwent individual culture and 449 controls whose embryos underwent group culture. There were no significant differences in fertilization rates between groups (81.7% for individual culture vs. 84.1% for group culture, p = 0.22). However, individual culture was associated with a decreased rate of blastocyst formation compared to group culture (43.5% vs. 48.5%, p < 0.01). Following single, vitrified-warmed euploid blastocyst transfer, there were no significant differences between individual culture and group culture, respectively, in rates of positive βhCG (81.9% vs. 81.5%, p = 0.91), sustained implantation (63.9% vs. 65.0%, p = 0.80), biochemical miscarriage (16.7% vs. 12.3%, p = 0.18), or clinical miscarriage (1.4% vs. 4.2%, p = 0.13).

CONCLUSION

While individual culture appears to negatively impact the rate of usable blastocyst formation compared to group culture, there were no significant differences in pregnancy outcomes following transfer of a single, vitrified-warmed euploid blastocyst.

Quality of embryos on day 7 after medium refreshment on day 6: a prospective trial

STUDY QUESTION

Are embryos that fail to meet biopsy or freezing criteria on day 6 (D6) more likely to meet these criteria on day 7 (D7) if cultured in fresh medium from D6 to D7?

SUMMARY ANSWER

Refreshment of medium on D6 did not increase the proportion of usable embryos on D7, with an adverse effect for women ≥40 years old.

WHAT IS KNOWN ALREADY

Embryo development in continuous single-step medium, from fertilization to the blastocyst stage, is equivalent to that using a sequential media protocol. However, there remains a theoretical benefit of refreshing the culture environment by transitioning slowly developing D6 embryos to a fresh medium droplet of the same composition, with a renewed source of nutrients and a milieu free of metabolic toxins.

STUDY DESIGN, SIZE, DURATION

This was a prospective trial of culture media exposure in which embryos were randomized on D6 to remain in the same culture medium from D3 to D7 (continuous, n = 620) or be moved to fresh medium (fresh, n = 603) on D6, with re-evaluation on D7. Data were collected from IVF cycles, with or without ICSI, between 29 March 2019 and 17 February 2020.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Embryos from 298 women, aged 18-44 years, from cycles with or without preimplantation genetic testing (PGT) that did not meet criteria for biopsy and/or freeze on D6 were included in the study. Embryos were only included if there was a minimum of two embryos meeting the inclusion criteria in any cohort. Only the first cycle undertaken by each woman in the study period from which embryos were randomized was included.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 1254 embryos were randomized from 312 cycles (209 non-PGT and 103 PGT) including 200 women undergoing IVF without PGT and 98 women who underwent PGT. The proportion of usable blastocysts on D7 did not differ between groups: 10.1% (61/603) in fresh versus 9.7% (60/620) in continuous medium (relative risk (RR) 1.05, 95% CI 0.74-1.47)). Embryos from women ≥40 years old had a significantly decreased likelihood of achieving a usable blastocyst on D7 after culture in fresh versus continuous medium: 3.5% versus 12.2%; RR 0.29, 95% CI 0.08-0.98. In total, 9.9% of embryos otherwise discarded on D6 met the criteria for biopsy and/or freeze on D7.

LIMITATIONS, REASONS FOR CAUTION

Future work investigating implantation, clinical pregnancy and miscarriage rates with D7 embryos is still needed.

WIDER IMPLICATIONS OF THE FINDINGS

Refreshment of medium on D6 did not increase the proportion of usable embryos on D7 overall. Younger women were more likely to develop D7 embryos after refreshment of medium on D6, while an adverse effect was seen in women ≥40 years old. However, by extending the culture of embryos to D7, additional blastocysts become available for clinical use.

STUDY FUNDING/COMPETING INTEREST(S)

Funding was provided through the Department of Obstetrics and Gynecology at Brigham and Women's Hospital. I.G.I. works with Teladoc Health. A.L. has no disclosures. E.S.G. works as a consultant for Teladoc Health, and a writer and editor for UpToDate and BioMed Central. C.R. is a board member of the American Society for Reproductive Medicine and works with UpToDate.

TRIAL REGISTRATION NUMBER

N/A.

Back to the future: optimised microwell culture of individual human preimplantation stage embryos

Although in vitro culture of human embryos is a crucial step in assisted reproduction, the lack of focused research hampers worldwide standardisation and consistent outcomes. Only 1.2% of research papers published in five leading journals in human reproduction in 2019 focused on in vitro culture conditions, creating the impression that the optimisation process has approached its limits. On the other hand, in vitro culture of mammalian embryos is based on old principles, while there is no consensus on basic issues as density, time, medium change, gas atmosphere and small technical details including the way of drop preparation. This opinion paper aims to highlight and analyse the slow advancement in this field and stimulate research for simple and affordable solutions to meet the current requirements. A possible way for advancement is discussed in detail. Selection of embryos with the highest developmental competence requires individual culture and modification of the widely used "drop under oil" approach. Current use of three-dimensional surfaces instead of large flat bottoms is restricted to time-lapse systems, but these wells are designed for optical clarity, not for the needs of embryos. The size and shape of the original microwells (Well of the Well; WOW) offer a practical and straightforward solution to combine the benefits of communal and individual incubation and improve the overall quality of cultured embryos.

Euploidy rates are not affected when embryos are cultured in a continuous (CCM) or sequential culture medium (SCM): a sibling oocyte study

PURPOSE

To determine if euploidy rates and embryo development differ when blastocysts are cultured in CCM or SCM.

METHOD

A single-center retrospective observational study was performed from September 2018 to March 2019. Patients [23-46 years] with at least four fresh mature oocytes (MII) without severe male factor infertility were included. Sibling MII were injected and cultured in Global®Total®LP (CCM) or Sage Quinn's Advantage® Cleavage and Blastocyst media (SCM) under 6% CO₂, 5% O₂, and 89% N₂. Fertilization, cleavage, day (D) 5 blastulation, usable blastocyst (blastocysts biopsied/normally fertilized oocytes), and euploidy rates were recorded. Blastocysts were graded prior to trophectoderm (TE) biopsy on D5, 6, or 7 for genetic testing and mitochondrial DNA (mtDNA) quantification.

RESULTS

According to clinical practice, 1452 MII were randomly distributed: 751 in CCM and 701 in SCM. No differences were observed in fertilization and cleavages rates for CCM and SCM (77.4% vs 75.5%, p = 0.429 and 97.6% vs 99.1%, p = 0.094, respectively). Blastulation rate on D5 was higher in CCM (70.6% vs 62.2, p = 0.009); however, usable blastocyst rates were comparable (CCM: 58.3% vs SCM: 56.7%, p = 0.625). From a Poisson regression model adjusted for confounding factors, euploidy rates were not different between media (aOR = 1.18, [0.94-1.48], p = 0.157). Euploid blastocyst's mtDNA values were similar (CCM: 32.2, [30.5, 34.1] and SCM: 33.5, [31.8, 35.2], p = 0.345) and top-quality blastocysts (AA/BA) were increased in SCM (OR=1.04, [1.00-1.09], p = 0.037).

CONCLUSION

Under controlled in vitro conditions, euploidy rates and embryo development are comparable when embryos are cultured in CCM or SCM.

Embryo blastulation and quality between days 5 and 6 of extended embryo culture

PURPOSE

This study aims to know what proportion of culture day 5 pre-blastocyst-stage embryos develop into blastocysts by culture day 6 and what patient and cycle characteristics are associated with delayed blastocyst formation.

METHODS

A retrospective observational cohort analysis was performed including a total of 9886 embryos from 1008 IVF cycles in 835 patients, who underwent treatment between January 1, 2016, and December 31, 2018. Autologous fresh in vitro fertilization (IVF) cycles at a single academic center were included in the analysis. Embryos were group-cultured using single-step culture media. Blastulation was defined as the presence of a new blastocyst. Usable blastulation was defined as the presence of a new good or excellent quality, expanded, hatching, or hatched blastocysts.

RESULTS

The mean blastulation rate between days 5 and 6 of extended embryo culture was 30.9%. The mean percentage of embryos developing into usable blastocyst-stage embryos was 19.8%. The factors associated with blastulation on day 6 included the total number of embryos and the number of pre-blastocysts on day 5, as well as the use of ICSI. Age, the number of total embryos, those remained in culture and pre-blastocysts, as well as the blastulation rate on day 5 were associated with usable blastulation.

CONCLUSION

It is important to know the usable blastocyst development rate between culture days 5 and 6 in order to adequately counsel patients debating whether to proceed with fresh ET on day 5 or forego ET with the expectation that embryos will be biopsied for PGT and/or cryopreserved on culture day 6. Our findings provide evidence to help guide patients in this difficult decision.

Fertility technologies and how to optimize laboratory performance to support the shortening of time to birth of a healthy singleton: a Delphi consensus

PURPOSE

To explore how the assisted reproductive technology (ART) laboratories can be optimized and standardized to enhance embryo culture and selection, to bridge the gap between standard practice and the new concept of shortening time to healthy singleton birth.

METHODS

A Delphi consensus was conducted (January to July 2018) to assess how the ART laboratory could be optimized, in conjunction with existing guidelines, to reduce the time to a healthy singleton birth. Eight experts plus the coordinator discussed and refined statements proposed by the coordinator. The statements were distributed via an online survey to 29 participants (including the eight experts from step 1), who voted on their agreement/disagreement with each statement. Consensus was reached if ≥ 66% of participants agreed/disagreed with a statement. If consensus was not achieved for any statement, that statement was revised and the process repeated until consensus was achieved. Details of statements achieving consensus were communicated to the participants.

RESULTS

Consensus was achieved for all 13 statements, which underlined the need for professional guidelines and standardization of lab processes to increase laboratory competency and quality. The most important points identified were the improvement of embryo culture and embryo assessment to shorten time to live birth through the availability of more high-quality embryos, priority selection of the most viable embryos and improved cryosurvival.

CONCLUSION

The efficiency of the ART laboratory can be improved through professional guidelines on standardized practices and optimized embryo culture environment, assessment, selection and cryopreservation methodologies, thereby reducing the time to a healthy singleton delivery.

Clinical Outcomes Deriving from Transfer of Blastocysts Developed in Day 7: a Systematic Review and Meta-Analysis of Frozen-Thawed IVF Cycles

This meta-analysis aimed to assess the reproductive competence of blastocysts developed on day 7 compared with blastocysts developed on day 5/6. A systematic search was carried out to select relevant studies published before January 2020. Ten retrospective observational cohort studies were included. The primary outcome was the clinical pregnancy rate (CPR). Secondary outcomes were live birth rate (LBR), euploid rate, and survival rates after thawing. Frozen-thawed day 7 blastocyst transfer was associated with a significant reduction in CPR compared to day 5/6 (OR 0.36 95% CI 0.21 to 0.62, p = 0.0002, I² = 71% and OR 0.43, 95% CI 0.32 to 0.58, p < 0.0001, I² = 17% respectively). A significantly lower proportion of LBR was found comparing blastocysts transfers in day 7 to those in day 5/6 (OR 0.21, 95% CI 0.16-0.27, p < 0.0001, I² = 0% and OR 0.34, 95% CI 0.26-0.45, p < 0.0001, I² = 0% respectively). These findings were confirmed in a subgroup of Preimplantation Genetic Testing for Aneuploidies (PGT-A)-screened blastocysts. Blastocysts biopsied in day 7 was associated with a significant decrease of euploid rate compared with day 5/6 (OR 0.47, 95% CI 0.39-0.57, p < 0.0001, I² = 69% and OR 0.68, 95% CI 0.61-0.75, p < 0.0001, I² = 19% respectively). The survival rate after thawing was not statistically different. Sensitivity analyses were also performed. This study shows an association between delayed blastulation and a poorer prognosis in terms of euploid rate and pregnancy outcomes following frozen-thawed transfers. On the other hand, the results do not support the discharge of slow-blastulation embryos.

[Impact of the type of incubator (non-humidified versus humidified) on embryo culture media osmolality]

INTRODUCTION

Benchtop incubators with small individual chambers have been developed in order to improve the stability of embryo culture conditions reducing the environmental stress during the embryo development. These new dry incubators were designed without any air humidification system in order to prevent bacterial proliferation and to enable the use of time-lapse system. However, an elevated evaporation of the culture media could occur in these conditions. The main objective of the study is to analyse the impact of the used incubator type on the embryo culture media osmolality.

MATERIALS AND METHODS

Microdrops of 50μL of culture media were placed in 60mm diameter culture dishes, and quickly covered with either 7 or 8mL of mineral oil in an IVF workstation with laminar airflow. Two series of culture dishes have been randomly placed either in a humidified incubator or in a dry benchtop incubator. The microdrops of each culture dishes were sampled at D0, D1, D2, D3, and D5 respectively to measure the osmolality in triplicate using a cryoscopic osmometer. The mean values of osmolality in each incubator have been compared respectively on D0, D1, D2, D3 and D5 with appropriate statistical tests, and considered statistically significant when P<0.05.

RESULTS

The osmolality of the microdrops placed in the dry benchtop incubator differed significantly after the third day of culture, regardless of the level of mineral oil in the culture dishes. Indeed, using Petri dishes covered respectively with 7 or 8mL of mineral oil, osmolality values of samples from the dry incubator were significantly higher than those from the humidified one, at D3 and D5 (D3/7mL: 273±2.1 vs. 268±1.0mOsm/kg; P=0.02; D3/8mL: 282±8.0 vs. 270±0.7mOsm/kg; P=0.04) and D5 (D5/7mL: 283±1.5 vs. 270±3.6mOsm/kg; P=0.004; D5/8mL: 287±5.6 vs. 268±2.3mOsm/kg; P=0.005). Furthermore, the analysis on paired samples showed that the osmolality in the dry benchtop incubator at D5 using 7mL of oil (283±1.5mOsm/kg; P=0.003) and at D3 (273±2.1mOsm/kg; P=0.016) and D5 (287±5.6mOsm/kg; P=0.009) using 8mL of oil was significantly higher than that measured at D0 (265±1.9mOsm/kg).

CONCLUSION

A significant increase of the embryo culture media osmolality was observed in the dry benchtop incubator with ambient hygrometry in our standard conditions. Adding 1mL of oil was not sufficient to reduce the evaporation of the media. Although maintained at a physiological level, the impact of the osmolality changes on the in vitro embryo development has to be further determined.

Use of time-lapse monitoring in medically assisted reproduction treatments: a mini-review

During human in vitro culture, a morphological microscope analysis is normally performed to select the best embryo to transfer, with the hope of obtaining a successful pregnancy. The morphological evaluation may combine number and size of blastomeres, fragmentation, multinucleation, blastocyst expansion, inner-cell mass and trophectoderm appearance. However, standard microscopy evaluation involves the removal of the embryos from the incubator, exposing them to changes in pH, temperature, and oxygen level. Additionally, morphological assessments might include high inter-observer variability. Recently, continuous embryo culture using time-lapse monitoring (TLM) has allowed embryologists to analyse the dynamic and morphokinetic events of embryo development and, based on that, the embryologist is able to scrutinize the complete sequence of embryonic evolution, from fertilization to the blastocyst formation. Therefore, TLM allows an uninterrupted culture condition, reducing the need to remove embryos from the incubator. The monitoring system is normally composed of a standard incubator with an integrated microscope coupled to a digital camera, which is able to collect images at regular times, and subsequently processed into video. These data can be annotated and analyzed using an integrated software, therefore this allows embryologists to facilitate the process of embryo selection for transfer. The main aim of this paper is to discuss the potential benefits and uses of the TLM in the embryology laboratory.

Blastulation rates of sibling oocytes in two IVF culture media: an evidence-based workflow to implement newly commercialized products

RESEARCH QUESTION

An evidence-based novel commercially available continuous IVF culture medium in compliance with an efficient quality-management system is proposed.

DESIGN

Non-interventional study on sibling oocytes. Intracytoplasmic sperm injection cycles among women aged 42 years or younger that used ejaculated spermatozoa and retrieved four to eight oocytes were included. Sibling oocytes were randomized for culture in the novel Geri-medium or continuous single culture medium (CSCM). Primary outcome measure was blastulation rate per cohort of inseminated oocytes; 1182 oocytes were required to outline down to a 7% difference (power = 80%).

RESULTS

A total of 181 cohorts of sibling oocytes were included. Geri-medium (n = 631 oocytes) and CSCM (n = 643 oocytes) resulted in similar blastulation rates (mean ± SD: 42.8% ± 30.1% versus 43.1% ± 29.0%; Wilcoxon signed rank test = 0.77). Blastocysts cultured in the former (n = 275 versus n = 277) showed longer timings during preimplantation development (P < 0.01) and were poorer quality (26% versus 18%; P = 0.03). Euploidy rate was no different in cycles that underwent preimplantation genetic testing for aneuploidy (n = 113) (117/237 [49%] versus 117/249 blastocysts [47%]; P = 0.6). Ongoing implantation rate was comparable in the study arms after euploid (29/47 [63%] versus 14/ 34 [41%]; P = 0.1) or untested (12/31 [39%] versus 7/18 [39%]; P = 0.3) transfers.

CONCLUSION

Blastulation rate among cohorts of sibling oocytes cultured in the same incubator is a fast, reliable and comprehensive performance indicator to validate novel commercially available culture medium. The media tested were considered similarly efficient. The differences in blastocyst morphology and developmental timings warrant further investigation, although euploidy and ongoing implantation rates were similar.

GM-CSF (granulocyte macrophage colony-stimulating factor) supplementation in culture media for women undergoing assisted reproduction

BACKGROUND

GM-CSF (granulocyte macrophage colony-stimulating factor) is a growth factor that is used to supplement culture media in an effort to improve clinical outcomes for those undergoing assisted reproduction. It is worth noting that the use of GM-CSF-supplemented culture media often adds a further cost to the price of an in vitro fertilisation (IVF) cycle. The purpose of this review was to assess the available evidence from randomised controlled trials (RCTs) on the effectiveness and safety of GM-CSF-supplemented culture media.

OBJECTIVES

To assess the effectiveness and safety of GM-CSF-supplemented human embryo culture media versus culture media not supplemented with GM-CSF, in women or couples undergoing assisted reproduction.

SEARCH METHODS

We used standard methodology recommended by Cochrane. We searched the Cochrane Gynaecology and Fertility Group Trials Register, CENTRAL, MEDLINE, Embase, CINAHL, LILACS, DARE, OpenGrey, PubMed, Google Scholar, and two trials registers on 15 October 2019, checked references of relevant papers and communicated with experts in the field.

SELECTION CRITERIA

We included RCTs comparing GM-CSF (including G-CSF (granulocyte colony-stimulating factor))-supplemented embryo culture media versus any other non-GM-CSF-supplemented embryo culture media (control) in women undergoing assisted reproduction.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures recommended by Cochrane. The primary review outcomes were live birth and miscarriage rate. The secondary outcomes were clinical pregnancy, multiple gestation, preterm birth, birth defects, aneuploidy, and stillbirth rates. We assessed the quality of the evidence using GRADE methodology. We undertook one comparison, GM-CSF-supplemented culture media versus culture media not supplemented with GM-CSF, for those undergoing assisted reproduction.

MAIN RESULTS

We included five studies, the data for three of which (1532 participants) were meta-analysed. We are uncertain whether GM-CSF-supplemented culture media makes any difference to the live-birth rate when compared to using conventional culture media not supplemented with GM-CSF (odds ratio (OR) 1.19, 95% confidence interval (CI) 0.93 to 1.52, 2 RCTs, N = 1432, I² = 69%, low-quality evidence). The evidence suggests that if the rate of live birth associated with conventional culture media not supplemented with GM-CSF was 22%, the rate with the use of GM-CSF-supplemented culture media would be between 21% and 30%. We are uncertain whether GM-CSF-supplemented culture media makes any difference to the miscarriage rate when compared to using conventional culture media not supplemented with GM-CSF (OR 0.75, 95% CI 0.41 to 1.36, 2 RCTs, N = 1432, I² = 0%, low-quality evidence). This evidence suggests that if the miscarriage rate associated with conventional culture media not supplemented with GM-CSF was 4%, the rate with the use of GM-CSF-supplemented culture media would be between 2% and 5%. Furthermore, we are uncertain whether GM-CSF-supplemented culture media makes any difference to the following outcomes: clinical pregnancy (OR 1.16, 95% CI 0.93 to 1.45, 3 RCTs, N = 1532 women, I² = 67%, low-quality evidence); multiple gestation (OR 1.24, 95% CI 0.73 to 2.10, 2 RCTs, N = 1432, I² = 35%, very low-quality evidence); preterm birth (OR 1.20, 95% CI 0.70 to 2.04, 2 RCTs, N = 1432, I² = 76%, very low-quality evidence); birth defects (OR 1.33, 95% CI 0.59 to 3.01, I² = 0%, 2 RCTs, N = 1432, low-quality evidence); and aneuploidy (OR 0.34, 95% CI 0.03 to 3.26, I² = 0%, 2 RCTs, N = 1432, low-quality evidence). We were unable to undertake analysis of stillbirth, as there were no events in either arm of the two studies that assessed this outcome.

AUTHORS' CONCLUSIONS

Due to the very low to low quality of the evidence, we cannot be certain whether GM-CSF is any more or less effective than culture media not supplemented with GM-CSF for clinical outcomes that reflect effectiveness and safety. It is important that independent information on the available evidence is made accessible to those considering using GM-CSF-supplemented culture media. The claims from marketing information that GM-CSF has a positive effect on pregnancy rates are not supported by the available evidence presented here; further well-designed, properly powered RCTs are needed to lend certainty to the evidence.

A novel culture medium with reduced nutrient concentrations supports the development and viability of mouse embryos

Further refinement of culture media is needed to improve the quality of embryos generated in vitro. Previous results from our laboratory demonstrated that uptake of nutrients by the embryo is significantly less than what is supplied in traditional culture media. Our objective was to determine the impact of reduced nutrient concentrations in culture medium on mouse embryo development, metabolism, and quality as a possible platform for next generation medium formulation. Concentrations of carbohydrates, amino acids, and vitamins could be reduced by 50% with no detrimental effects, but blastocyst development was impaired at 25% of standard nutrient provision (reduced nutrient medium; RN). Addition of pyruvate and L-lactate (+PL) to RN at 50% of standard concentrations restored blastocyst development, hatching, and cell number. In addition, blastocysts produced in RN + PL contained more ICM cells and ATP than blastocysts cultured in our control (100% nutrient) medium; however, metabolic activity was altered. Similarly, embryos produced in the RN medium with elevated (50% control) concentrations of pyruvate and lactate in the first step medium and EAA and Glu in the second step medium were competent to implant and develop into fetuses at a similar rate as embryos produced in the control medium. This novel approach to culture medium formulation could help define the optimal nutrient requirements of embryos in culture and provide a means of shifting metabolic activity towards the utilization of specific metabolic pathways that may be beneficial for embryo viability.

Evaluation of seminal oxidation-reduction potential in male infertility

The role of oxidative stress in male infertility has been broadly recognised, and the search for a new marker to determine the redox environment in semen has gained considerable interest. Oxidation-reduction potential (ORP) or redox potential, is a measure of the electron transfer from antioxidants to oxidants and provides information on the redox balance. In this review, the benefits of ORP as a new oxidative stress marker, the protocol for its evaluation and the importance of its measurement in the context of male infertility are discussed. In association with the standard semen analysis, seminal ORP has been analysed to evaluate semen quality and male fertility status. However, further studies are required to establish its use in assisted reproductive techniques (ART) practice.

Time-lapse technology for embryo culture and selection

Culturing of human embryos in optimal conditions is crucial for a successful in vitro fertilisation (IVF) programme. In addition, the capacity to assess and rank embryos correctly for quality will allow for transfer of the potentially 'best' embryo first, thereby shortening the time to pregnancy, although not improving cumulative pregnancy and live birth rates. It will also encourage and facilitate the implementation of single embryo transfers, thereby increasing safety for mother and offspring. Time-lapse technology introduces the concept of stable culture conditions, in connection with the possibility of continuous viewing and documenting of the embryo throughout development. However, so far, even when embryo quality scoring is based on large datasets, or when using the time-lapse technology, the morphokinetic scores are still mainly based on subjective and intermittent annotations of morphology and timings. Also, the construction of powerful algorithms for widespread use is hampered by large variations in culture conditions between individual IVF laboratories. New methodology, involving machine learning, where every image from the time-lapse documentation is analysed by a computer programme, looking for patterns that link to outcome, may in the future provide a more accurate and non-biased embryo selection.

Type of protein supplement in cryopreservation solutions impacts on the degree of ultrastructural damage in frozen-thawed human oocytes

Protein sources used as supplements of IVF culture media are known to have several implications for the function and stability of embryo culture environment. In fact, they i) transport biologically active molecules ii) chelate heavy metals, iii) regulate media pH, iii) scavenge reactive oxygen species (ROS) and iv) attenuate osmotic stress to which cells are exposed in sub-optimal culture conditions. Instead, their specific relevance to the formulation of cryopreservation solutions used for gamete and embryo cryopreservation remains uncertain. In the present work, we tested the hypothesis that different protein supplements present in cryopreservation solutions, serum or plasma protein solution (PPS), or different concentrations of the same supplement (serum), are associated with different types and/or magnitude of cryopreservation-derived cell damage. To this end, using cryopreservation solutions containing serum or PPS, donated supernumerary human mature oocytes were frozen-thawed by slow freezing and compared with fresh controls. Ultrastructural markers of oocyte quality were adopted as objective measure to assess possible damage from cryopreservation. The study results indicate that the adoption of serum minimises cell damage induced by cryopreservation. Indeed, typical hallmarks of cryodamage in human oocytes, i.e. loss of cortical granules, zona pellucida hardening and above all vacuolization, were largely reduced in oocytes cryopreserved with solutions containing serum, especially if used a higher concentration. This suggest that oocyte cryopreservation still has significant margins of improvement that may derive also from composition of cryopreservation media.

The impact of selected embryo culture conditions on ART treatment cycle outcomes: a UK national study

STUDY QUESTION

Are selected embryo culture conditions namely media, oxygen level, and incubator type, associated with IVF live birth rate (LBR) and the health of singleton offspring at birth?

SUMMARY ANSWER

There were statistically significant differences in LBR between the eight culture media systems analysed; however, none of the embryo culture factors showed statistically significant associations with birth weight (BW) in multivariable regression analyses.

WHAT IS KNOWN ALREADY

In clinical ART culture media is the initial environment provided for the growth of human embryos. Pre-implantation development is a critical period of developmental plasticity, which could have long-lasting effects on offspring growth and health. Although some studies have shown an impact of culture medium type on BW, the interaction between culture medium type and associated culture conditions on both treatment success rates (LBR) and offspring BW is largely unexplored. This study aimed to examine these factors in a large multicentre national survey capturing the range of clinical practice.

STUDY DESIGN, SIZE, DURATION

In this cross-sectional study, data from a survey circulated to all UK IVF clinics requesting information regarding culture medium type, incubator type, and oxygen level used in ART between January 2011 and December 2013 were merged with routinely recorded treatment and outcome data held in the Human Fertilisation and Embryology Authority Register up to the end of 2014.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Forty-six (62%) UK clinics responded to the survey. A total of 75 287 fresh IVF/ICSI cycles were captured, including 18 693 singleton live births. IVF success (live birth, singleton or multiple; LB), singleton gestation and singleton gestation-adjusted BW were analysed using logistic and linear regression models adjusting for patient/treatment characteristics and clinic-specific effects.

MAIN RESULTS AND THE ROLE OF CHANCE

Culture medium type was shown to have some impact on LBR (multivariable logistic regression, (MRL); post-regression Wald test, P < 0.001), but not on BW (MLR; post-regression Wald test, P = 0.215). However, blastocyst culture had the largest observed effect on odds of LBR (odds ratio (OR) = 1.35, CI: 1.29–1.42), increased the risk of pre-term birth even when controlling for oxygen tension (MLR; OR = 1.42, CI: 1.23–1.63), and gestation-adjusted BW (MLR, β = 38.97 g, CI: 19.42–58.53 g) when compared to cleavage-stage embryo culture. We noted a very strong effect of clinic site on both LBR and BW, thus confounding between treatment practices and clinic site may have masked the effect of culture conditions.

LIMITATIONS, REASONS FOR CAUTION

Larger datasets with more inter-centre variation are also needed, with key embryo culture variables comprehensively recorded in national treatment registries.

WIDER IMPLICATIONS OF THE FINDINGS

This study is the largest investigation of laboratory environmental effects in IVF on both LBR and singleton BW. Our findings largely agree with the literature, which has failed to show a consistent advantage of one culture media type over another. However, we noted some association of LBR with medium type, and the duration of embryo exposure to laboratory conditions (blastocyst culture) was associated with both LBR and singleton health at birth. Because of the strong effect of clinic site noted, further randomized controlled trials are needed in order to reliably determine the effect of embryo culture on IVF success rates and the growth and health of subsequent offspring.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by the EU FP7 project grant EpiHealthNet (FP7-PEOPLE-2012-ITN -317 146). The authors have no competing interests to declare.

The impact of culture conditions on blastocyst formation and aneuploidy rates: a comparison between single-step and sequential media in a large academic practice

PURPOSE

To compare a single-step medium with a sequential medium on human blastocyst development rates, aneuploidy rates, and clinical outcomes.

METHODS

Retrospective cohort study of IVF cycles that used Sage advantage sequential medium (n = 347) and uninterrupted Sage 1-step medium (n = 519) from July 1, 2016, to December 31, 2017, in an academic fertility center. Main outcome measures are blastocyst formation rates per two-pronuclear (2PN) oocyte and aneuploidy rates per biopsy.

RESULTS

Of all IVF cycles, single-step medium yielded higher blastocyst formation rate (51.7% vs 43.4%) but higher aneuploidy rate (54.0% vs 45.8%) compared with sequential medium. When stratified by maternal age, women under age 38 had no difference in blastocyst formation (52.2% vs 50.2%) but a higher aneuploidy rate (44.5% vs 36.4%) resulting in a lower number of euploid blastocysts per cycle (2.6 vs 3.3) when using single-step medium compared to sequential medium. In cycles used single-step medium, patients ≥ age 38 had higher blastocyst rate (48.0% vs 33.6%), but no difference in aneuploidy rate (68.8% vs 66.0%) or number of euploid embryos (0.8 vs 1.1). For patients reaching euploid embryo transfer, there was no difference in clinical pregnancy rates, miscarriage rates, or live birth rates between two culture media systems.

CONCLUSIONS

Our study demonstrates an increase in aneuploidy in young women whose embryos were cultured in a single-step medium compared to sequential medium. This study highlights the importance of culture conditions on embryo ploidy and the need to stratify by patient age when examining the impact of culture conditions on overall cycle potential.

Maternal Yes-Associated Protein Participates in Porcine Blastocyst Development via Modulation of Trophectoderm Epithelium Barrier Function

The establishment of a functional trophectoderm (TE) epithelium is an essential prerequisite for blastocyst formation and placentation. Transcription coactivator yes-associated protein (YAP), a downstream effector of the hippo signaling pathway, is required for specification of both the TE and epiblast lineages in mice. However, the biological role of YAP in porcine blastocyst development is not known. Here, we report that maternally derived YAP protein is localized to both the cytoplasm and nuclei prior to the morula stage and is then predominantly localized to the TE nuclei in blastocysts. Functionally, maternal YAP knockdown severely impeded blastocyst formation and perturbed the allocation of the first two lineages. The treatment of embryos with verteporfin, a pharmacological inhibitor of YAP, faithfully recapitulated the phenotype observed in YAP deleted embryos. Mechanistically, we found that maternal YAP regulates multiple genes which are important for lineage commitment, tight junction assembly, and fluid accumulation. Consistent with the effects on tight junction gene expression, a permeability assay revealed that paracellular sealing was defective in the trophectoderm epithelium. Lastly, YAP knockdown in a single blastomere at the 2-cell stage revealed that the cellular progeny of the YAP⁺ blastomere were sufficient to sustain blastocyst formation via direct complementation of the defective trophectoderm epithelium. In summary, these findings demonstrate that maternal YAP facilitates porcine blastocyst development through transcriptional regulation of key genes that are essential for lineage commitment, tight junction assembly, and fluid accumulation.