Cryopreservation of human embryos by vitrification or slow freezing: a systematic review and meta-analysis

Effect of estrogen exposure on pregnancy outcomes in artificial frozen-thawed embryo transfer cycles

In contemporary times, the employment of vitrification freezing technology has led to the widespread adoption of frozen-thawed embryo transfer (FET) worldwide. Meanwhile, hormone replacement therapy (HRT) is a crucial protocol for priming the endometrium during FET cycles. Estrogen is required in HRT cycles for the induction of progesterone receptors and to promote endometrial thickness. However, there is no universal consensus on the treatment duration, dosage regimen, administration route, and target serum estrogen levels. Therefore, this study aimed to offer a comprehensive review of these topics. A shorter duration of estrogen exposure may elevate the risk of early miscarriage, while prolonged exposure to estrogen does not seem to confer advantages to general population and may be attempted in individuals with thin endometrium. Moreover, excessive estrogen levels on the day of progesterone administration may be associated with higher miscarriage rates and lower live birth rates (LBR). To offer more comprehensive guidance for clinical practice, extensive and prospective studies involving a large sample size are warranted to determine the optimal concentration and duration of estrogen exposure.

Mourning the frozen: considering the relational implications of cryonics

Cryonics is the preservation of legally dead human bodies at the temperature of liquid nitrogen in the hope that future technologies will be able to revive them. In philosophical debates surrounding this practice, arguments often focus on prudential implications of cryopreservation, or moral arguments on a societal level. In this paper, we claim that this debate is incomplete, since it does not take into account a significant relational concern about cryonics. Specifically, we argue that attention should be paid to the potential implications of cryopreservation for the mourning processes of surviving loved ones. Cryopreservation increases the likelihood of disruption of the practical and mental tasks involved in a successful mourning process, which can negatively impact survivors of the cryopreserved patient. To illustrate my argument, we will draw on a case study from the 2019 documentary Hope Frozen We aim to introduce this concern, in order to gain a more complete view on the potential implications of cryopreservation.

Oncofertility as an Essential Part of Comprehensive Cancer Treatment in Patients of Reproductive Age, Adolescents and Children

The number of children, adolescents and young adults diagnosed with cancer has been rising recently. Various oncological treatments have a detrimental effect on female fertility, and childbearing becomes a major issue during surveillance after recovery. This review discusses the impact of oncological treatments on the ovarian reserve with a thorough explanation of oncologic treatments' effects and modes of oncofertility procedures. The aim of this review is to help clinicians in making an informed decision about post-treatment fertility in their patients. Ultimately, it may lead to improved overall long-term outcomes among young populations suffering from cancer.

Natural proliferative phase frozen embryo transfer-a new approach which may facilitate scheduling without hindering pregnancy outcomes

STUDY QUESTION

How does a natural proliferative phase (NPP) strategy for frozen embryo transfer (FET) compare with the conventional artificial (AC) and natural (NC) endometrial preparation protocols in terms of live birth rates (LBR)?

SUMMARY ANSWER

This study supports the hypothesis that, just as for NC, NPP-FET may be a superior alternative to AC in terms of LBR.

WHAT IS KNOWN ALREADY

Although FETs are increasing worldwide, the optimal FET protocol is still largely controversial. Despite recent evidence supporting a possibly higher efficacy and safety of NC FETs, their widespread use is limited by the difficulties encountered during cycle monitoring and scheduling.

STUDY DESIGN, SIZE, DURATION

In this single center retrospective cohort study, we describe the NPP-FET protocol, in which vaginal progesterone is initiated during the proliferative phase as soon as an endometrium with a thickness of at least 7 mm is identified and ovulation is ruled out, regardless of mean diameter of the dominant follicle.

PARTICIPANTS/MATERIALS, SETTING, METHODS

For comparison, we considered all blastocyst stage FET cycles preformed at a private infertility center between January 2010 and June 2022, subdivided according to the following subgroups of endometrial preparation: AC, NPP, and NC. We performed multivariable generalized estimating equations regression analysis to account for the following potential confounding variables: oocyte age at retrieval, oocyte source (autologous without preimplantation genetic testing for aneuploidies (PGT-A) versus autologous with PGT-A versus donated), number of oocytes retrieved/donated, embryo developmental stage (Day 5 versus Day 6), number of embryos transferred, quality of the best embryo transferred, and year of treatment. The main outcome measure was LBR. The secondary outcomes included hCG positive, clinical pregnancy and miscarriage rates, and the following perinatal outcomes: first trimester bleeding, second/third trimester bleeding, preterm rupture of membranes, gestational diabetes, gestational hypertensive disorders (GHD), and gestational age at delivery.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 5791 FET cycles were included in this analysis (2226 AC, 349 NPP, and 3216 NC). The LBR for FET was lower in the AC subgroup when compared to the NPP and NC (38.4%, 49.1%, and 45.2%, respectively; P < 0.01 AC versus NPP and AC versus NC). The rates of miscarriage were also lower in the NPP and NC subgroups when compared to AC (19.7%, 25.0%, and 34.9%, respectively; P < 0.01 NPP versus AC and NC versus AC). Considering perinatal outcomes, NPP-FET and NC were associated with a significantly lower first trimester bleeding compared to AC (17.3%, 14.7%, and 37.6%, respectively; P < 0.01 NPP versus AC and NC versus AC). Additionally, NC was associated with a lower rate of GHD when compared with AC (8.6% versus 14.5%, P < 0.01), while the rate following NPP-FET was 9.4%.

LIMITATIONS, REASONS FOR CAUTION

This study is limited by its retrospective design. Moreover, there was also a low number of patients in the NPP subgroup, which may have led the study to be underpowered to detect clinically relevant differences between the subgroups.

WIDER IMPLICATIONS OF THE FINDINGS

Our study posits that the NPP-FET protocol may be an effective and safe alternative to both NC and AC, while still allowing for enhanced practicality in patient follow-up and FET scheduling. Further investigation on NPP-FET is warranted, with prospective studies including a larger and more homogeneous subsets of patients.

STUDY FUNDING/COMPETING INTEREST(S)

This research was supported by the IVI-RMA-Lisbon (2008-LIS-053-CG). The authors did not receive any funding for this study. The authors have no competing interests.

TRIAL REGISTRATION NUMBER

Not applicable.

Long-term embryo vitrification is associated with reduced success rates in women undergoing frozen embryo transfer following a failed fresh cycle

OBJECTIVE

To investigate the association of long-term embryo vitrification with the success rates and neonatal outcomes in frozen cycles.

STUDY DESIGN

A single-center, retrospective cohort study was performed in Peking University Third Hospital. We included women who had undergone their first vitrified-warmed cycles following an unsuccessful fresh embryo transfer cycle between January 2013 and December 2019. Restricted cubic splines with 4 knots (at min-3.0 months, 3.1-6.0 months, 6.1-12.0 months, 12.1-max months) were used to map the non-linear relationship between live birth and embryo storage time as a continuous variable after adjustment for covariates. Multiple logistic regression was used to calculate crude odds ratios (OR) and adjusted OR (aOR) with 95 % confidence intervals (CI).

RESULTS

A total of 10,167 women undergoing their first frozen cycle following an unsuccessful fresh embryo transfer cycle were included, among whom 3,708 resulted in a live birth (3,254 singleton live births). Restricted cubic splines, both before and after adjusting for covariates, showed that the predicted live birth rate (LBR) progressively decreased with an increase in the duration of embryo cryopreservation. This trend was also evident when women were categorized into four groups based on the length of cryopreservation. The live birth rate (LBR) was highest in the 0.8-3.0 months group (38 %) compared to the other groups. Multivariable logistic regression with the 0.8-3.0 months group as the reference, demonstrated that the 6.1-12.0 months group and >12.0 months group experienced lower live birth rates (aOR = 0.82 (0.72, 0.94) and aOR = 0.71 (0.57, 0.88), respectively). The LBR for the 3.1-6.0 months group was comparable to that of the 0.8-3.0 months group, with an aOR of 0.98 (0.90, 1.07). Sensitivity analyses in women who underwent single blastocyst transfer, in women with at least one good-quality embryo for transfer, and in women with age less than 36 at embryo transfer demonstrated a similar association between LBR and embryo frozen time. The neonatal outcomes were not significantly different among the four groups.

CONCLUSIONS

Embryo vitrification greater than six months is associated with a reduction in success rate but does not appear to alter neonatal outcome.

External bending of cryodevice during vitrification leads to cryoprotectant cracks and damage to embryo blastomeres

RESEARCH QUESTION

Embryo blastomeres and the zona pellucida are occasionally damaged during vitrification; is this a result of crack-induced mechanical damage in the glass state, caused by external bending of the device?

DESIGN

A stereomicroscope was used to observe external bending-induced cracks in a cryoprotectant. Thereafter, 309 human cleavage-stage embryos derived from abnormally fertilized eggs were used to assess embryo damage under two external bending conditions: forward bending and backward bending, with three bending degrees applied. Three distinct embryo positions were used to examine the correlation between bending and embryo damage. Damage was assessed by looking at blastomere lysis rates, and overall rates of damaged and surviving embryos.

RESULTS

A series of parallel cracks were identified in the cryoprotectant used for external bending, which led to damage to the embryo blastomeres. Compared with forward bending and control, the embryos were found to be more easily damaged by backward bending, indicated by significantly higher blastomere lysis and embryo damage rates, and lower embryo survival rate of backward bending than forward bending (P < 0.001). The degree of embryo damage also increased as the degree of external forces increased. Embryo position correlated with degree of embryo damage.

CONCLUSIONS

Cryoprotectant crack-induced damage was identified as the cause of embryo damage. Mechanical damage to the glass state occurs because of improper external bending of the cryodevice strip in liquid nitrogen during vitrification. To prevent damage, bending of the strip should be avoided and the embryos should be placed near the tip of the strip.

Study on the optimal time limit of frozen embryo transfer and the effect of a long-term frozen embryo on pregnancy outcome

In this retrospective study conducted at Sichuan Jinxin Xinan Women and Children's Hospital spanning January 2015 to December 2021, our objective was to investigate the impact of embryo cryopreservation duration on outcomes in frozen embryo transfer. Participants, totaling 47,006 cycles, were classified into 3 groups based on cryopreservation duration: ≤1 year (Group 1), 1 to 6 years (Group 2), and ≥6 years (Group 3). Employing various statistical analyses, including 1-way ANOVA, Kruskal-Wallis test, chi-square test, and a generalized estimating equation model, we rigorously adjusted for confounding factors. Primary outcomes encompassed clinical pregnancy rate and Live Birth Rate (LBR), while secondary outcomes included biochemical pregnancy rate, multiple pregnancy rate, ectopic pregnancy rate, early and late miscarriage rates, preterm birth rate, neonatal birth weight, weeks at birth, and newborn sex. Patient distribution across cryopreservation duration groups was as follows: Group 1 (40,461 cycles), Group 2 (6337 cycles), and Group 3 (208 cycles). Postcontrolling for confounding factors, Group 1 exhibited a decreased likelihood of achieving biochemical pregnancy rate, clinical pregnancy rate, and LBR (OR < 1, aOR < 1, P < .05). Furthermore, an elevated incidence of ectopic pregnancy was observed (OR > 1, aOR > 1), notably significant after 6 years of freezing time [aOR = 4.141, 95% confidence intervals (1.013-16.921), P = .05]. Cryopreservation exceeding 1 year was associated with an increased risk of early miscarriage and preterm birth (OR > 1, aOR > 1). No statistically significant differences were observed in birth weight or sex between groups. However, male infant birth rates were consistently higher than those of female infants across all groups. In conclusion, favorable pregnancy outcomes align with embryo cryopreservation durations within 1 year, while freezing for more than 1 year may diminish clinical pregnancy and LBRs, concurrently elevating the risk of ectopic pregnancy and preterm birth.

Conduction-Dominated Cryomesh for Organism Vitrification

Vitrification-based cryopreservation is a promising approach to achieving long-term storage of biological systems for maintaining biodiversity, healthcare, and sustainable food production. Using the "cryomesh" system achieves rapid cooling and rewarming of biomaterials, but further improvement in cooling rates is needed to increase biosystem viability and the ability to cryopreserve new biosystems. Improved cooling rates and viability are possible by enabling conductive cooling through cryomesh. Conduction-dominated cryomesh improves cooling rates from twofold to tenfold (i.e., 0.24 to 1.2 × 105  °C min-1 ) in a variety of biosystems. Higher thermal conductivity, smaller mesh wire diameter and pore size, and minimizing the nitrogen vapor barrier (e.g., vertical plunging in liquid nitrogen) are key parameters to achieving improved vitrification. Conduction-dominated cryomesh successfully vitrifies coral larvae, Drosophila embryos, and zebrafish embryos with improved outcomes. Not only a theoretical foundation for improved vitrification in µm to mm biosystems but also the capability to scale up for biorepositories and/or agricultural, aquaculture, or scientific use are demonstrated.

Automation in vitrification and thawing of mouse oocytes and embryos

Vitrification is a common technique for cryopreserving oocytes or embryos. However, manual vitrification is tedious and labor-intensive, and can be subject to variations caused by human factors. To address these challenges, we developed an automated vitrification-thawing system (AVTS) based on a cryo-handle. Our study firstly assessed the efficiency of cryoprotectant exchange through comparing the osmolalities of fresh and collected solutions during automated vitrification and thawing, and evaluated the cooling and warming rates of the cryo-handle. We also compared mouse oocyte survival, fertilization and embryo development after thawing and ICSI, and the development of re-frozen cleavage embryos between manual operation and automated system. The results showed that the osmolalities of collected samples were within normal range and comparable to fresh solutions. Furthermore, the automated system could obtain the reliable cooling and warming rates. Particularly, there were no significant differences in oocyte survival rates, fertilization rates, and subsequent embryo development and its quality between two procedures. Our findings suggest that AVTS has no impact on osmolalities of vitrification and thawing solutions, ensuring the proper exchange of cryoprotectants. The cryo-handle also shows the ability to achieve reliable cooling and warming rates, which benefits for the cryopreservation and thawing process. Moreover, the results from mouse oocytes and embryos indicate that automated system has effectively maintained the survival and fertilization of frozen oocytes and supported subsequent embryo development. Therefore, the automated vitrification and thawing system will inevitably represent a superior alternative to manual operation.

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.

From oocytes to a live birth: Are we improving the biological efficiency?

OBJECTIVE(S)

The objectives of our study were to investigate the live birth rate (LBR) per oocyte retrieved during in vitro fertilization, in patients who had used all their embryos and to extrapolate the LBR in patients with remaining frozen embryos by calculating the expected LBR from these embryos.

DESIGN

A retrospective cohort study.

SETTING

A single academically affiliated fertility clinic.

PATIENT(S)

Autologous in vitro fertilization cycles from January 2014 to December 2020. Data on the number of oocytes retrieved, number of embryos obtained and transferred (at cleavage or blastocyst-stage), use of preimplantation genetic testing for aneuploidy (PGT-A), and number of live births were obtained. The expected LBR was estimated in patients with remaining frozen embryos according to nationally reported Society for Assisted Reproductive Technology LBR data.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Live birth rate per oocyte retrieved.

RESULT(S)

A total of 12,717 patients met the inclusion criteria and underwent a total of 20,677 oocyte retrievals which yielded a total of 248,004 oocytes and 57,268 embryos (fresh and frozen). In patients who had fully utilized all their embryos the LBR per oocyte was 2.82% (ranging from 11.3% aged <35 years to 1.2% aged >42 years). Stratification of the population based on PGT-A utilization yielded similar results (with PGT-A: 2.88% and without PGT-A: 2.79%). When stratified by the Society for Assisted Reproductive Technology age groups, the addition of PGT-A in patients aged 35-37 and 38-40 years yielded higher LBR per oocyte compared with patients who did not add PGT-A (P<.05). In patients with remaining frozen embryos who had added PGT-A, the projected LBR per oocyte was 8.34%. Use of PGT-A in patients aged <35 and 35-37 years decreased LBR per oocyte (P<.001 and P=.03, respectively) but improved LBR per oocyte in patients aged 38-40 and 41-42 years (P=.006 and P=.005, respectively). Poisson regression analysis demonstrated an age threshold of 38.5, below which PGT-A lowers LBR per oocyte compared with no PGT-A.

CONCLUSION(S)

Despite clinical and scientific advances in Assisted Reproductive Technology, with the current protocols of ovarian stimulation, the LBR per oocyte remains low reflecting a biological barrier that has yet to be overcome. Overall, the addition of PGT-A did not demonstrate improved outcomes.

Comparison of the duration of estradiol administration and the effect on pregnancy outcome of day 3 vitrified-warmed embryo transfer cycle: a randomized controlled trial

Based on the fact that the follicular phase in the menstrual cycle has length variation, it has been assumed that the duration of oestrogen (E2) administration could also be variable; therefore, for the first time, this randomized clinical trial study was conducted to investigate and compare the duration of estradiol administration and the effect on pregnancy outcomes in the cleavage-stage frozen embryo transfer (FET) cycle. We included women aged 20-40 with a normal uterus on hysteroscopy between September and December 2022 and who were divided randomly into three groups: group A [n = 79; 8-11 days of oestrogen before progesterone (P4) supplementation], group B (n = 78; 12-14 days of oestrogen before P4 supplementation), and group C (n = 76; 15-18 days of estrogen before P4 supplementation). Serum levels for E2 on the initial progesterone day and P4 on the transfer day were measured. The effect of the duration of E2 administration on clinical pregnancy and pregnancy loss was investigated. We found no significant differences between the three groups in the clinical pregnancy rate (P = 0.696) and clinical abortion rate (P = 0.925) according to the duration of the E2. There was no significant difference in the E2, P4 levels, and endometrial thickness in pregnant vs. non-pregnant women. The mean of the E2 and P4 levels was 300.03 ± 22.21 and 25.36 ± 5.78, respectively. Our findings suggest that variation in the length of E2 administration (8-18 days) before progesterone initiation in day 3 FET cycles does not affect pregnancy outcome and transfer time can be flexibly arranged.

Finding of the optimal preparation and timing of endometrium in frozen-thawed embryo transfer: a literature review of clinical evidence

Frozen-thawed embryo transfer (FET) has been a viable alternative to fresh embryo transfer in recent years because of the improvement in vitrification methods. Laboratory-based studies indicate that complex molecular and morphological changes in endometrium during the window of implantation after exogenous hormones with controlled ovarian stimulation may alter the interaction between the embryo and endometrium, leading to a decreased implantation potential. Based on the results obtained from randomized controlled studies, increased pregnancy rates and better perinatal outcomes have been reported following FET. Compared to fresh embryo transfer, fewer preterm deliveries, and reduced incidence of ovarian hyperstimulation syndrome were found after FETs, yet there is a trend of increased pregnancy-related hypertensive diseases in women receiving FET. Despite the increased application of FET, the search for the most optimal priming protocol for the endometrium is still undergoing. Three available FET protocols have been proposed to prepare the endometrium: i) natural cycle (true natural cycle and modified natural cycle) ii) artificial cycle (AC) or hormone replacement treatment cycle iii) mild ovarian stimulation (mild-OS) cycle. Emerging evidence suggests that the optimal timing for FET using warmed blastocyst transfer is the LH surge+6 day, hCG administration+7 day, and the progesterone administration+6 day in the true natural cycle, modified natural cycle, and AC protocol, respectively. Although still controversial, better clinical pregnancy rates and live birth rates have been reported using the natural cycle (true natural cycle/modified natural cycle) compared with the AC protocol. Additionally, a higher early pregnancy loss rate and an increased incidence of gestational hypertension have been found in FETs using the AC protocol because of the lack of a corpus luteum. Although the common clinical practice is to employ luteal phase support (LPS) in natural cycles and mild-OS cycles for FET, the requirement for LPS in these protocols remains equivocal. Recent findings obtained from RCTs do not support the routine application of endometrial receptivity testing to optimize the timing of FET. More RCTs with rigorous methodology are needed to compare different protocols to prime the endometrium for FET, focusing not only on live birth rate, but also on maternal, obstetrical, and neonatal outcomes.

Freeze-all embryos during treatment with assisted reproduction: Health economic aspects

Assisted reproductive technologies are evolving, with the most recent example being the introduction of the freeze-all policy during which a fresh embryo transfer does not take place and all embryos of good quality are cryopreserved to be used in future frozen embryo transfers. As the freeze-all policy is becoming more prevalent, it is important to review the economic aspects of this approach, along with considerations of efficacy and safety, and the role of emerging freeze-all-specific ovarian stimulation strategies. Based on the available evidence, the freeze-all policy presents distinct clinical advantages, particularly for high responders. Available health economic evaluations are limited. Two good-quality cost-effectiveness analyses based on randomized controlled trials suggest that the freeze-all strategy is unlikely to be cost-effective in non-polycystic ovarian syndrome (non-PCOS), normally responding patients. However, the cost-effectiveness of the freeze-all strategy in different populations of patients and in different settings has not been evaluated, nor has the clinical and economic efficacy of modern freeze-all-specific ovarian stimulation protocols that are likely to simplify treatment and make it more affordable for patients. Economic evaluations that incorporate good practice health technology assessment (HTA) methods are needed to compare freeze-all with conventional embryo transfer strategies. Furthermore, future research should address the unique limitation of traditional HTA methods in valuing a life conceived through fertility treatment.

The Effect of Short-Term Aspirin Administration during Programmed Frozen-Thawed Embryo Transfer on Pregnancy Outcomes and Complications

Low-dose aspirin is widely used during frozen-embryo transfer (FET) cycles. Its anti-platelet property makes it a potentially useful drug for the prevention of hypertension disorders of pregnancy (HDP). However, the existing evidence about the effect of short-term aspirin administration on pregnancy outcomes is not clear. In our study, we retrospectively investigated women who had their first or second FET cycles at the Reproductive Hospital Affiliated with Shandong University from April 2017 to December 2020. A total of 4454 programmed FET cycles were recruited. According to whether aspirin was administrated in the protocols, the patients were divided into two groups: The Control group (n = 2793, 85 of them using donor sperm) and the Aspirin group (n = 1661, 35 of them using donor sperm). We analyzed the pregnancy outcomes and pregnancy complications of these cycles and observed similar live birth rates. We found that the short-term use of aspirin at a dosage of 50 mg per day for women undergoing programmed FET did not elevate the live birth rate or decrease the incidence of a series of pregnancy complications, including HDP. Based on our experience, short-term administration of low-dose aspirin may not improve the outcomes of young women undergoing frozen-thawed embryo transfer cycles.

Effect of vaginal flora on clinical outcome of frozen embryo transfer

Objective

Vaginal microbiota imbalance is a high risk factor for premature birth, and is closely related to female pelvic inflammation and sexually transmitted diseases. The effect of vaginal microbiota on the outcome of assisted reproductive technology is still unclear. In this study, the vaginal microbial composition and the pregnancy outcome of frozen embryo transfer (FET) was investigated.

Methods

From October 2020 to December 2021, 275 FET cycles were selected from the center of reproductive medicine in Affiliated Hospital of Nantong University. Vaginal secretions were collected on the day of endometrium transformation, and smears were Gram stained. According to the Nugent score they were divided into three groups, including normal group, mild dysbiosis group and sever dysbiosis group. The clinical outcomes of each group were compared.

Results

In 275 FET cycles, the embryo implantation rate, clinical pregnancy rate and ongoing pregnancy rate in the normal group (66.9%,84.3% and 83.1%) were significantly higher than those in the mild dysbiosis group (45.5%, 57.3% and 49.3%) and in sever dysbiosis group (29.6%, 34.2% and 27%). The difference was statistically significant (P<0.01). When compared the preclinical pregnancy loss rate and the miscarriage rate, the normal group (1.3% and 1.3%) was significantly lower than those in the mild dysbiosis group (20.4% and 14.0%) and the sever dysbiosis group (25.5% and 21.1%). The difference was statistically significant (P<0.01), but there was no significant difference between the mild dysbiosis group and sever dysbiosis group (P>0.05).

Conclusion

Nugent score is directly related to the clinical outcome of FET. The Lactobacilli-dominant vaginal flora was a favorable factor for the good clinical outcome of FET, while asymptomatic bacterial vaginosis had a negative correlation with the outcome of FET.

Impact of different endometrial preparation protocols before frozen embryo transfer on pregnancy outcomes: a review

The use of frozen embryo transfer cycles has exponentially increased in the last few years. Optimization of endometrial preparation protocols before frozen embryo transfer is mandatory to further improve pregnancy outcomes. This review will focus on the existing literature with regard to the different available endometrial preparation protocols and their impact on pregnancy outcomes. More specifically, we will focus on programmed, natural, and stimulated frozen embryo transfer cycles. The studies performed on this topic are generally of low quality, and only a few well-performed randomized controlled trials have been published. To date, no strong evidence is available to support the use of 1 preparation method over another in terms of pregnancy outcomes. However, robust data have shown a clearly protective effect of natural frozen embryo transfer cycles against long-term obstetric complications, mainly hypertensive disorders of pregnancy and large for gestational age infants. The introduction of individualized luteal phase support in different endometrial preparation protocols is actually gaining a lot of attention and requires further investigation.

Endometrial Cancer in Reproductive Age: Fertility-Sparing Approach and Reproductive Outcomes

Endometrial cancer is the most common gynecologic malignancy in developed countries and approximately 7% of the women with endometrial cancer are below the age of 45. Management of endometrial cancer in young women who desire to maintain fertility presents a unique set of challenges since the standard surgical treatment based on hysterectomy and salpingo-oophorectomy is often not compatible with the patient's goals. A fertility-preserving approach can be considered in selected patients with early stage and low-grade endometrial cancer. An increasing amount of data suggest that oncologic outcomes are not compromised if a conservative approach is utilized with close monitoring until childbearing is completed. If a fertility-preserving approach is not possible, assisted reproductive technologies can assist patients in achieving their fertility goals.

Rapid joule heating improves vitrification based cryopreservation

Cryopreservation by vitrification has far-reaching implications. However, rewarming techniques that are rapid and scalable (both in throughput and biosystem size) for low concentrations of cryoprotective agent (CPA) for reduced toxicity are lacking, limiting the potential for translation. Here, we introduce a joule heating-based platform technology, whereby biosystems are rapidly rewarmed by contact with an electrical conductor that is fed a voltage pulse. We demonstrate successful cryopreservation of three model biosystems with thicknesses across three orders of magnitude, including adherent cells (~4 µm), Drosophila melanogaster embryos (~50 µm) and rat kidney slices (~1.2 mm) using low CPA concentrations (2-4 M). Using tunable voltage pulse widths from 10 µs to 100 ms, numerical simulation predicts that warming rates from 5 × 104 to 6 × 108 °C/min can be achieved. Altogether, our results present a general solution to the cryopreservation of a broad spectrum of cellular, organismal and tissue-based biosystems.

Effects of vitrified cryopreservation duration on IVF and neonatal outcomes

Background

In this study, we aimed to evaluate the impact of the duration of cryopreservation storage on embryo viability, implantation competence, pregnancy outcome and neonatal outcomes.

Methods

We retrospectively evaluated the outcomes of patients who underwent IVF with vitrified cryopreserved embryos between January 2004 and August 2019 by following the first frozen embryo transfer cycles within the study period. A total of 31,143 patients met the inclusion criteria and were grouped according to the embryo storage time as follows: Group 1 (n = 20,926),1–90 days; Group 2 (n = 6,472), 91–180 days; Group 3 (n = 2,237), 181–365 days; Group 4 (n = 746), 366–730 days; and Group 5 (n = 762), > 731 days.

Results

The embryo survival rate decreased significantly with longer durations of cryopreservation. The highest and lowest survival rate was recorded in Group 1 and Group 5, respectively (34853/35338; 98.63% vs. 1281/1801; 71.13%; P < 0.01). The human chorionic gonadotropin (HCG) detection and clinical pregnancy rate was highest in Group 1 (57.85% and 55. 26%, respectively; P < 0.01). Short-term cryopreservation (≤ 3 months) is associated with higher rates of clinical pregnancy. There were no significant differences in neonatal birth weight, neonatal height and congenital anomalies among the groups (P > 0. 05).

Conclusion

The prolonged storage time of vitrified embryos negatively affected survival rate and clinical pregnancy rate. It did not have a significant influence on neonatal health. This study provides new findings about the relationship between prolonged storage time of vitrified embryos and clinical outcomes and offers evidence for the safety of using long-stored embryos after vitrification.

Impact of cell loss after warming of human vitrified day 3 embryos on obstetric outcome in single frozen embryo transfers

PURPOSE

Does cell loss (CL) after vitrification and warming (V/W) of day 3 embryos have an impact on live birth rate (LBR) and neonatal outcomes?

METHOD

This retrospective analysis includes cleavage stage day 3 embryos vitrified/warmed between 2011 and 2018. Only single vitrified/warmed embryo transfers were included. Pre-implantation genetic screening, oocyte donation, and age banking were excluded from the analysis. The sample was divided into two groups: group A (intact embryo after warming) and group B (≤ 50% blastomere loss after warming).

RESULTS

On the total embryos (n = 2327), 1953 were fully intact (83.9%, group A) and 374 presented cell damage (16.1%, group B). In group B, 62% (232/374) of the embryos had lost only one cell. Age at cryopreservation, cause of infertility, insemination procedure, and semen origin were comparable between the two groups. The positive hCG rate (30% and 24.3%, respectively, for intact vs CL group, p = 0.028) and LBR (13.7% and 9.4%, respectively, for intact vs CL group, p = 0.023) per warming cycle were significantly higher for intact embryos. However, LBR per positive hCG was equivalent between intact and damaged embryos (45.6% vs 38.5%, respectively, p = 0.2). Newborn measurements (length, weight, and head circumference at birth) were comparable between the two groups. Multivariate logistic regression showed that the presence of CL is not predictive for LB when adjusting for patients' age.

CONCLUSIONS

LBR is significantly higher after transfer of an intact embryo compared to an embryo with CL after warming; however, neonatal outcomes are comparable between the two groups.

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.

Pro: Fresh versus frozen embryo transfer. Is frozen embryo transfer the future?

Embryo cryopreservation has been an integral part of ART for close to 40 years and vitrification has boosted overall ART efficacy and safety. Recently, there has been a vivid scientific discussion on whether elective cryopreservation of all embryos (freeze-all) should be pursued for most patients, with a fresh embryo transfer taking place only in selected cases. In terms of efficacy, the available evidence suggests that the freeze-all strategy leads to higher live birth rates after the first embryo transfer compared to the conventional strategy in high responders, while there is no difference in normal responders. There is no evidence to suggest that the freeze-all strategy is inferior to the conventional strategy of fresh transfer when comparing cumulative live birth rates using data from all available randomized controlled trials. The incidence of ovarian hyperstimulation syndrome is significantly reduced in the freeze-all policy. However, regarding obstetric complications and neonatal outcomes, the evidence suggests that each strategy is associated with certain risks and, therefore, there is no approach that could be unequivocally accepted as safer. Similarly, limited evidence does not support the notion that patients would be universally against freeze-all owing to the inevitable delay in pregnancy achievement. Finally, the cost-effectiveness of freeze-all is likely to vary in different settings and there have been studies supporting that this policy can be, under certain conditions, cost-effective. Adoption of the freeze-all policy can also allow for more flexible treatment strategies that have the potential to increase efficacy, reduce cost and make treatment easier for patients and clinics. Importantly, freeze-all does not require the use of any experimental technologies, further training of personnel or the costly acquisition of new equipment. For these reasons, transitioning to the freeze-all policy for most patients appears to be the next logical step in ART.

The impact of blastomere loss on pregnancy and neonatal outcomes of vitrified-warmed Day3 embryos in single embryo transfer cycles

BACKGROUND

Blastomere loss is a common phenomenon that occurs following cryopreservation. To date, studies have drawn conflicting conclusions regarding the impact of blastomere loss on pregnancy outcomes. Besides, limited information is available concerning the neonatal safety of embryos with blastomere loss. In the present study, we aimed to investigate the impact of blastomere loss on pregnancy and neonatal outcomes of vitrified/warmed Day3 cleavage-stage embryos in single embryo transfer cycles.

METHODS

This retrospective cohort study included all vitrified/warmed D3 cleavage-stage single frozen-thawed embryo transfer (FET) cycles between April 2015 and February 2021. We compared pregnancy and subsequent neonatal outcomes between the intact embryos group and the blastomere loss group in single FET cycles.

RESULTS

A total of 6287 single FET cycles were included in the study, in which 5873 cycles were classified into the intact embryo group and 414 cycles were classified into the blastomere loss group. The outcomes of the blastomere loss group were significantly inferior to those of the intact embryo group, in terms of implantation/biochemical pregnancy/clinical pregnancy/ongoing pregnancy rate and live birth rate per embryo transfer cycle/per clinical pregnancy. Further binary logistic regression confirmed that blastomere loss was negatively associated with live birth. Moreover, the blastomere loss group presented with an elevated early miscarriage rate. The neonatal conditions were broadly similar between the two groups. Additionally, multiple binary logistic regression analysis demonstrated that primary infertility and intracytoplasmic sperm injection (ICSI) were common influencing factors of blastomere loss (aOR 1.447, 95% CI 1.038-2.019, P = 0.029; aOR: 1.388, 95% CI: 1.044-51.846, P = 0.024).

CONCLUSIONS

The transfer of vitrified/warmed D3 embryos with blastomere loss is related to impaired embryo developmental potentials and reduced probabilities of conception. Moreover, even if the embryos with blastomere loss have implanted and reached clinical pregnancies, they present with a lower possibility of developing to live birth owing to a higher early miscarriage rate. However, once the embryos with blastomere loss result in a live birth, no adverse neonatal outcomes are observed. Primary infertility and ICSI were found to be risk factors for blastomere loss.

Algorithm-based individualization methodology of the starting gonadotropin dose in IVF/ICSI and the freeze-all strategy prevent OHSS equally in normal responders: a systematic review and network meta-analysis of the evidence

PURPOSE

Ovarian hyperstimulation syndrome (OHSS) represents a rare but dangerous condition associated with controlled ovarian stimulation (COS) in IVF/ICSI. Over the last decades, many strategies have been introduced into clinical practice with the objective of preventing this potentially life-threatening condition. Among these, the freeze-all policy has gained great popularity, thanks to improvements in vitrification. Nevertheless, not all clinics have adequate skills in vitrification procedures and patients may be dissatisfied with a longer time to pregnancy.

METHODS

This study is a systematic review and network meta-analysis of randomized controlled trials comparing different strategies of ovarian stimulation in IVF/ICSI cycles (freeze-all policy, algorithm-based individualization of the starting dose, experience-based individualization of the starting dose, standard dose) in terms of reduction of OHSS, in normal responders.

RESULTS

The results indicate that only the algorithm-based individualization of the starting gonadotropin dose reduces OHSS similarly to the freeze-all strategy.

CONCLUSION

Albeit in the era of the freeze-all policy, the personalization of the starting gonadotropin dose obtained by the use of algorithms should be pursued as a valid and safe option for IVF.

A comparison of frozen-thawed embryo transfer protocols in 2920 single-blastocyst transfers

OBJECTIVE

To assess the effect of frozen-thawed embryo transfer (FET) protocol on live-birth rate (LBR) and clinical pregnancy rate (CPR), in single-vitrified-blastocyst transfer MATERIALS AND METHODS: Retrospective cohort study with FET of a single-blastocyst embryos (n = 2920 cycles) thawed 2013-2018. FET protocols were natural cycles (NC-FET) (n = 147), artificial hormone replacement treatment cycles (HRT-FET) (n = 2645), and modified NC (mNC) with hCG triggering (n = 128). Primary outcome was LBR. Adjustment for age, embryo grade, year of freezing\thawing, infertility cause, and endometrial thickness was performed.

RESULTS

There were no significant differences between the groups with regard to female age, embryo grade, and endometrial thickness. LBR was higher in the mNC compared to HRT-FET cycles (38.3% vs. 20.9% P < 0.0001), and in the NC compared to HRT-FET cycles (34.7% vs. 20.9%, P = 0.0002). CPR was higher in the mNC compared to HRT-FET cycles (46.1% vs. 33.3% P = 0.0003), and in the NC compared to HRT-FET cycles (45.9% vs. 33.3%, P = 0.002). There was no significant difference in LBR or CPR between NC-FET and mNC-FET. Higher LBR with NC-FET and mNC-FET remained significant after adjusting for confounders (aOR 2.42, 95%CI 1.53-3.66, P < 0.0001).

CONCLUSION

The use of the convenient artificial HRT-FET cycles must be cautiously reconsidered in light of the potential negative effect on LBR when compared with natural cycle FET.

Ovarian Stimulation in Assisted Reproductive Technology Cycles for Varied Patient Profiles: An Indian Perspective

Controlled ovarian stimulation has been an integral part of in vitro fertilisation (IVF) treatment cycles. Availability of different gonadotropins for ovarian stimulation and gonadotropin releasing hormone (GnRH) analogues for prevention of premature rise of leutinising hormone during follicular phase offer an opportunity to utilise them for a successful outcome in women with different subsets of ovarian response. Further, use of GnRH agonist as an alternative for human chorionic gonadotropin improves safety of ovarian stimulation in hyper-responders. Mild ovarian stimulation protocols have emerged as an alternative to conventional protocols in the recent years. Individualisation plays an important role in improving safety of IVF in hyper-responders while efforts continue to improve efficacy in poor responders. Some of the follicular and peri-ovulatory phase interventions may be associated with negative impact on the luteal phase and segmentalisation of the treatment with frozen embryo transfer may be an effective strategy in such a clinical scenario. This narrative review looks at the available evidence on various aspects of ovarian stimulation strategies and their consequences. In addition, it provides a concise summary of the evidence that has emerged from India on various aspects of ovarian stimulation.

Fatty Acid Supplementation During in vitro Embryo Production Determines Cryosurvival Characteristics of Bovine Blastocysts

In vitro production (IVP) embryos have a reduced quality and poor cryotolerance in comparison to in vivo embryos. This study investigated whether free fatty acid (FFA) conditions, fatty acid free (FAF)- synthetic oviduct fluid (SOF) without or with 25 μM of saturated stearic (C_18:0) or unsaturated oleic (C_18:1) acid during the first 5 IVP days, relate to quality and cryosurvival of day 8 blastocysts. Apart from the blastocyst scores, both 1) number and size of lipid droplets of fresh blastocysts and 2) total number and apoptotic and necrotic cells, before and after freezing-thawing, were scored by confocal microscopy. Blastocyst rates were significantly lower in the FAF SOF condition in comparison to other groups. Interestingly, blastocysts originating from the C_18:1 group, with a significantly higher lipid content, and blastocysts from the FAF SOF group demonstrated a high cryosurvival rate (70.1 and 67.4%, respectively) comparable with in vivo blastocysts (68%), in contrast to the poor cryosurvival of C_18:0 exposed embryos (17.6%). In all freeze-thawed embryos the average amount of apoptotic and necrotic cells increased albeit that the C_18:0 condition rates were higher (43.2%) when compared to C_18:1 (26.0%) and FAF SOF conditions (26.5%). The current data show that FFA administered during early embryonic development significantly affect the cryotolerance of blastocysts.

Population-wide contribution of medically assisted reproductive technologies to overall births in Australia: temporal trends and parental characteristics

STUDY QUESTION

In a country with supportive funding for medically assisted reproduction (MAR) technologies, what is the proportion of MAR births over-time?

SUMMARY ANSWER

In 2017, 6.7% of births were conceived by MAR (4.8% ART and 1.9% ovulation induction (OI)/IUI) with a 55% increase in ART births and a stable contribution from OI/IUI births over the past decade.

WHAT IS KNOWN ALREADY

There is considerable global variation in utilization rates of ART despite a similar infertility prevalence worldwide. While the overall contribution of ART to national births is known in many countries because of ART registries, very little is known about the contribution of OI/IUI treatment or the socio-demographic characteristics of the parents. Australia provides supportive public funding for all forms of MAR with no restrictions based on male or female age, and thus provides a unique setting to investigate the contribution of MAR to national births as well as the socio-demographic characteristics of parents across the different types of MAR births.

STUDY DESIGN, SIZE, DURATION

This is a novel population-based birth cohort study of 898 084 births using linked ART registry data and administrative data including birth registrations, medical services, pharmaceuticals, hospital admissions and deaths. Birth (a live or still birth of at least one baby of ≥400 g birthweight or ≥20 weeks’ gestation) was the unit of analysis in this study. Multiple births were considered as one birth in our analysis.

PARTICIPANTS/MATERIALS, SETTING, METHODS

This study included a total of 898 084 births (606 488 mothers) in New South Wales and the Australian Capital Territory, Australia 2009–2017. We calculated the prevalence of all categories of MAR-conceived births over the study period. Generalized estimating equations were used to examine the association between parental characteristics (parent’s age, parity, socio-economic status, maternal country of birth, remoteness of mother’s dwelling, pre-existing medical conditions, smoking, etc.) and ART and OI/IUI births relative to naturally conceived births.

MAIN RESULTS AND THE ROLE OF CHANCE

The proportion of MAR births increased from 5.1% of all births in 2009 to 6.7% in 2017, representing a 30% increase over the decade. The proportion of OI/IUI births remained stable at around 2% of all births, representing 32% of all MAR births. Over the study period, ART births conceived by frozen embryo-transfer increased nearly 3-fold. OI/IUI births conceived using clomiphene citrate decreased by 39%, while OI/IUI births conceived using letrozole increased 56-fold. Overall, there was a 55% increase over the study period in the number of ART-conceived births, rising to 56% of births to mothers aged 40 years and older. In 2017, almost one in six births (17.6%) to mothers aged 40 years and over were conceived using ART treatment. Conversely, the proportion of OI/IUI births was similar across different mother’s age groups and remained stable over the study period. ART children, but not OI/IUI children, were more likely to have parents who were socio-economically advantaged compared to naturally conceived children. For example, compared to naturally conceived births, ART births were 16% less likely to be born to mothers who live in the disadvantaged neighbourhoods after accounting for other covariates (adjusted relative risk (aRR): 0.84 [95% CI: 0.81–0.88]). ART- or OI/IUI-conceived children were 25% less likely to be born to immigrant mothers than births after natural conception (aRR: 0.75 [0.74–0.77]).

LIMITATIONS, REASONS FOR CAUTION

The social inequalities that we observed between the parents of children born using ART and naturally conceived children may not directly reflect disparities in accessing fertility care for individuals seeking treatment.

WIDER IMPLICATIONS OF THE FINDINGS

With the ubiquitous decline in fertility rates around the world and the increasing trend to delay childbearing, this population-based study enhances our understanding of the contribution of different types of MARs to population profiles among births in high-income countries. The parental socio-demographic characteristics of MAR-conceived children differ significantly from naturally conceived children and this highlights the importance of accounting for such differences in studies investigating the health and development of MAR-conceived children.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded through Australian National Health and Medical Research Council (NHMRC) grant: APP1127437. G.M.C. is an employee of The University of New South Wales (UNSW) and Director of the National Perinatal Epidemiology and Statistics Unit (NPESU), UNSW. The NPESU manages the Australian and New Zealand Assisted Reproduction Database with funding support from the Fertility Society of Australia and New Zealand. C.V. is an employee of The University of New South Wales (UNSW), Director of Clinical Research of IVFAustralia, Member of the Board of the Fertility Society of Australia and New Zealand, and Member of Research Committee of School of Women’s and Children’s Health, UNSW. C.V. reports grants from Australian National Health and Medical Research Council (NHMRC), and Merck KGaA. C.V. reports consulting fees, and payment or honoraria for lectures, presentations, speakers, bureaus, manuscript, writing or educational events or attending meeting or travel from Merck, Merck Sparpe & Dohme, Ferring, Gedon-Richter and Besins outside this submitted work. C.V. reported stock or stock options from Virtus Health Limited outside this submitted work. R.J.N. is an employee of The University of Adelaide, and Chair DSMC for natural therapies trial of The University of Hong Kong. R.J.N. reports grants from NHMRC. R.J.N. reports lecture fees and support for attending or travelling for lecture from Merck Serono which is outside this submitted work. L.R.J. is an employee of The UNSW and Foundation Director of the Centre for Big Data Research in Health at UNSW Sydney. L.R.J. reports grants from NHMRC. The other co-authors have no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Preserving Oocytes in Oncofertility†

The prodigious rise of cancer survival rates enables many cancer survivors to live long lives. Therefore, the side effects of cancer treatments as well as the long-term quality of life after cancer have become more relevant. Ovarian toxicity is a major off-target effect of anticancer agents for childhood and young adult female cancer patients. Both chemotherapy and irradiation have been demonstrated to damage the ovary and increase the risks of premature ovarian failure (POF), early menopause, ovarian endocrine disorders, and sub- or infertility. Oncofertility is an emerging and multidisciplinary research and medical field that focuses on providing cancer patients with fertility preservation options. Oocyte quality and quantity are one of the most important factors to determine women's fertility success; therefore, preserving oocytes is paramount for maintaining the ability of young female cancer patients' reproduction after their recovery. This review summarizes peer-reviewed literature on current oocyte preservation options in oncofertility. We describe in-depth oocyte and embryo cryopreservation, ovarian suppression, ovarian tissue cryopreservation, in vitro maturation, ovarian transposition, and adjuvant therapy. Further, we discuss current guidelines and practices of female fertility preservation that cover preserving oocytes.

A comparative study of post-warming survival rates and clinical outcomes of human blastocysts vitrified/warmed by CryoTouch and Cryotop methods

OBJECTIVE

Advances in embryo culture conditions and the development of vitrification as a revolutionary cryopreservation method have allowed for routine use of blastocyst transfer in assisted reproduction technology (ART) cycles. Several vitrification/warming media and devices have been introduced for commercial use so far. The aim of this retrospective study was to compare post-warming survival rates and clinical outcomes of human blastocysts vitrified/warmed by two different commercial methods (CryoTouch and Cryotop) during ART cycles.

METHODS

This retrospective study assessed a total of 50 frozen embryo transfer (FET) cycles conducted on 56 warmed blastocysts between January 2018 and December 2020. Post-warming blastocyst survival rates and clinical outcomes including clinical pregnancy and live birth rates were calculated after single blastocyst transfer cycles.

RESULTS

The results revealed no significant differences between two groups in post-warming survival rate (p-value=0.8381), clinical pregnancy rate (p-value=0.8157) and live birth rate (p-value=0.7041).

CONCLUSIONS

Post-warming survival rates and clinical outcomes were comparable with no significant difference in blastocysts vitrified/warmed by CryoTouch and Cryotop commercial methods.

Assessing couples' preferences for fresh or frozen embryo transfer: a discrete choice experiment

STUDY QUESTION

What are couples' preferences for fresh embryo transfer versus freezing of all embryos followed by frozen embryo transfer and the associated clinical outcomes that may differentiate them?

SUMMARY ANSWER

Couples' preferences are driven by anticipated chances of live birth, miscarriage, neonatal complications, and costs but not by the differences in the treatment process (including delay of embryo transfer linked to frozen embryo transfer and risk of ovarian hyperstimulation syndrome (OHSS) associated with fresh embryo transfer).

WHAT IS KNOWN ALREADY

A policy of freezing all embryos followed by transfer of frozen embryos results in livebirth rates which are similar to or higher than those following the transfer of fresh embryos while reducing the risk of OHSS and small for gestational age babies: it can, however, increase the risk of pre-eclampsia and large for gestational age offspring. Hence, the controversy continues over whether to do fresh embryo transfer or freeze all embryos followed by frozen embryo transfer.

STUDY DESIGN, SIZE, DURATION

We used a discrete choice experiment (DCE) technique to survey infertile couples between August 2018 and January 2019.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We asked IVF naïve couples attending a tertiary referral centre to independently complete a questionnaire with nine hypothetical choice tasks between fresh and frozen embryo transfer. The alternatives varied across the choice occurrences on several attributes including efficacy (live birth rate), safety (miscarriage rate, neonatal complication rate), and cost of treatment. We assumed that a freeze-all strategy prolonged treatment but reduced the risk of OHSS. An error components mixed logit model was used to estimate the relative value (utility) that couples placed on the alternative treatment approaches and the attributes used to describe them. Willingness to pay and marginal rates of substitution between the non-cost attributes were calculated. A total of 360 individual questionnaires were given to 180 couples who fulfilled the inclusion criteria, of which 212 were completed and returned Our study population included 3 same sex couples (2 females and 1 male) and 101 heterosexual couples. Four questionnaires were filled by one partner only. The response rate was 58.8%.

MAIN RESULTS AND THE ROLE OF CHANCE

Couples preferred both fresh and frozen embryo transfer (odds ratio 27.93 and 28.06, respectively) compared with no IVF treatment, with no strong preference for fresh over frozen. Couples strongly preferred any IVF technique that offered an increase in live birth rates by 5% (P = 0.006) and 15% (P < 0.0001), reduced miscarriage by 18% (P < 0.0001) and diminished neonatal complications by 10% (P < 0.0001). Respondents were willing to pay an additional £2451 (95% CI 604 - 4299) and £761 (95% CI 5056-9265) for a 5 and 15% increase in the chance of live birth, respectively, regardless of whether this involved fresh or frozen embryos. They required compensation of £5230 (95% CI 3320 - 7141) and £13 245 (95% CI 10 110-16 380) to accept a 10 and 25% increase in the risk of neonatal complications, respectively (P < 0.001). Results indicated that couples would be willing to accept a 1.26% (95% CI 1.001 - 1.706) reduction in the live birth rate for a 1% reduction in the risk of neonatal complications per live birth. Older couples appeared to place less emphasis on the risk of neonatal complications than younger couples.

LIMITATIONS, REASONS FOR CAUTION

DCEs can elicit intentions which may not reflect actual behaviour. The external validity of this study is limited by the fact that it was conducted in a single centre with generous public funding for IVF. We cannot rule out the potential for selection or responder bias.

WIDER IMPLICATIONS OF THE FINDINGS

If a strategy of freeze all was to be implemented it would appear to be acceptable to patients, if either success rates can be improved or neonatal complications reduced. Live birth rates, neonatal complication rates, miscarriage rates, and cost are more likely to drive their preferences than a slight delay in the treatment process. The results of this study have important implications for future economic evaluations of IVF, as they suggest that the appropriate balance needs to be struck between success and safety. A holistic approach incorporating patient preferences for expected clinical outcomes and risks should be taken into consideration for individualized care.

STUDY FUNDING/COMPETING INTEREST(S)

No external funding was sought for this study. A.M. is the chief investigator of the randomized controlled trial 'Freeze all'. S.B. is an Editor in Chief of Human Reproduction Open. The other co-authors have no conflicts of interest to declare. Graham Scotland reports non-financial support from Merck KGaA, Darmstadt, Germany, outside the submitted work.

TRIAL REGISTRATION NUMBER

N/A.

Post-warming survival rates and clinical outcomes of human cleavage stage embryos vitrified/warmed using CryoTouch and Cryotop methods

Background

Vitrification has become the method of choice for cryopreservation of human embryos and gametes. There are multiple commercial media, containing different combinations and concentrations of cryoprotectants, available for vitrification and warming procedures. The aim of this retrospective study was to compare post-warming survival rate and clinical outcomes of cleavage stage embryos vitrified/warmed using two different commercial methods (CryoTouch and Cryotop) during intracytoplasmic sperm injection/frozen embryo transfer (ICSI/FET) cycles. This retrospective study evaluated a total of 173 FET cycles performed on 446 warmed cleavage stage embryos between January 2018 and December 2020. Post-warming embryo survival rate and clinical outcomes including clinical pregnancy, implantation, and live birth rates were calculated.

Results

The results showed no significant differences between two groups in terms of post-warming survival rate (p value = 0.5020), clinical pregnancy rate (p value = 0.7411), implantation rate (p value = 0.4694), and live birth rate (p value = 0.5737).

Conclusions

Collectively, high successful rates were observed in outcomes of vitrified/warmed cleavage stage embryos using both CryoTouch and Cryotop commercial methods.

A randomised, multi-center, open trial comparing a semi-automated closed vitrification system with a manual open system in women undergoing IVF

STUDY QUESTION

What are outcome and procedural differences when using the semi-automated closed Gavi® device versus the manual open Cryotop® method for vitrification of pronuclear (2PN) stage oocytes within an IVF program?

SUMMARY ANSWER

A semi-automated closed vitrification method gives similar clinical results as compared to an exclusively manual, open system but higher procedure duration and less staff convenience.

WHAT IS KNOWN ALREADY

A semi-automated closed vitrification device has been introduced to the market, however, little evaluation of its performance in a clinical setting has been conducted so far.

STUDY DESIGN, SIZE, DURATION

This prospective, randomised, open non-inferiority trial was conducted at three German IVF centers (10/2017-12/2018). Randomization was performed on day of fertilization check, stratified by center and by indication for vitrification (surplus 2PN oocytes in the context of a fresh embryo transfer (ET) cycle or 'freeze-all' of 2PN oocytes).

PARTICIPANT/MATERIAL, SETTING, METHODS

The study population included subfertile women, aged 18-40 years, undergoing IVF or ICSI treatment after ovarian stimulation, with 2PN oocytes available for vitrification. The primary outcome was survival rate of 2PN oocytes at first warming procedure in a subsequent cycle and non-inferiority of 2PN survival was to be declared if the lower bound 95% CI of the mean difference in survival rate excluded a difference larger than 9.5%; secondary, descriptive outcomes included embryo development, pregnancy and live birth rate, procedure time and staff convenience.

MAIN RESULTS AND THE ROLE OF CHANCE

The randomised patient population consisted of 149 patients, and the per-protocol population (patients with warming of 2PN oocytes for culture and planned ET) was 118 patients. The survival rate was 94.0% (±13.5) and 96.7% (±9.7) in the Gavi® and the Cryotop® group (weighted mean difference -1.6%, 95% CI -4.7 to 1.4, P = 0.28), respectively, indicating non-inferiority of the Gavi® vitrification/warming method for the primary outcome. Embryo development and the proportion of top-quality embryos was similar in the two groups, as were the pregnancy and live birth rate. Mean total procedure duration (vitrification and warming) was higher in the Gavi® group (81 ± 39 min vs 47 ± 15 min, mean difference 34 min, 95% CI 19 to 48). Staff convenience assessed by eight operators in a questionnaire was lower for the Gavi® system. The majority of respondents preferred the Cryotop® method because of practicality issues.

LIMITATIONS, REASON FOR CAUTION

The study was performed in centers with long experience of manual vitrification, and the relative performance of the Gavi® system as well as the staff convenience may be higher in settings with less experience in the manual procedure. Financial costs of the two procedures were not measured along the trial.

WIDER IMPLICATIONS OF THE FINDINGS

With increasing requirements for standardization of procedures and tissue safety, a semi-automated closed vitrification method may constitute a suitable alternative technology to the established manual open vitrification method given the equivalent clinical outcomes demonstrated herein.

STUDY FUNDING/COMPETING INTERESTS

The trial received no direct financial funding. The Gavi® instrument, Gavi® consumables and staff training were provided for free by the distributor (Merck, Darmstadt, Germany) during the study period. The manufacturer of the Gavi® instrument had no influence on study protocol, study conduct, data analysis, data interpretation or manuscript writing. J.H. has received honoraria and/or non-financial support from Ferring, Merck and Origio. G.G. has received honoraria and/or non-financial support from Abbott, Ferring, Finox, Gedeon Richter, Guerbet, Merck, MSD, ObsEva, PregLem, ReprodWissen GmbH and Theramex. The remaining authors have no competing interests.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov NCT03287479.

TRIAL REGISTRATION DATE

19 September 2017.

DATE OF FIRST PATIENT’S ENROLMENT

10 October 2017.

Factors associated with vitrification-warming survival in 6167 euploid blastocysts

PURPOSE

To understand the clinical factors associated with embryo survival after vitrification in a cohort of human blastocysts screened by preimplantation genetic testing for aneuploidy (PGT-A).

METHODS

Patient demographic, embryo, and cycle characteristics associated with failed euploid blastocyst survival were compared in a cohort of women (n = 6167) who underwent IVF-PGT-A.

RESULTS

Compared to those that survived warming, vitrified euploid embryos that failed to survive after warming came from IVF cycles with significantly higher estradiol levels at time of surge (2754.8 ± 1390.2 vs. 2523.1 ± 1190.6 pg/mL, p = 0.03), number of oocytes retrieved (19.6 ± 10.7 vs. 17.5 ± 9.8, p = 0.005), and basal antral follicle count (BAFC) (15.3 ± 8.5 vs. 13.9 ± 7.2, p = 0.05). Euploid embryos were less likely to survive warming if they came from cycles before 2015 (24.6% vs. 13.2%, p < 0.001), were cryopreserved on day 7 versus day 5 or 6 (9.1% vs. 3.0%, p < 0.001), underwent two trophectoderm biopsies (6.9% vs. 2.3%, p < 0.001), had a grade C inner cell mass (15.4% vs. 7.7%, p < 0.001), or were fully hatched (41.1% vs. 12.2%, p < 0.001). In the multivariate model, which controlled for relevant confounders, the association between decreased survival and increased BAFC, year of IVF cycle, double trophectoderm biopsy, and fully hatched blastocysts remained statistically significant.

CONCLUSION

Euploid embryos that are fully hatched at time of vitrification, come from patients with high ovarian reserve, or require repeat trophectoderm biopsy are less likely to survive vitrification-warming. Our results provide a framework for reproductive counseling and offer realistic expectations to patients about the number of embryos needed to achieve family building goals.

Vitrification improves in-vitro embryonic survival in Bos taurus embryos without increasing pregnancy rate post embryo transfer when compared to slow-freezing: A systematic meta-analysis

Objectives were to use meta-analytic approaches to compare slow-freezing (SF) and vitrification (VF) methods of cryopreservation on in-vitro (n = 12,211) and in-vivo (n = 3473) survival of Bos taurus embryos. The literature was systematically reviewed and data from 40 manuscripts including 78 experiments, and comprising 183 treatment means, were used for the analyses. The in-vitro parameters included rates of re-expansion, hatching, and survival of blastocysts either at 24 h or 72 h post-thawing/warming and total number (TN) of embryonic cells, whereas in-vivo parameters evaluated pregnancy rate between 35 and 60 d post embryo transfer (ET). Mixed models were fitted using MIXED and GLIMMIX procedures of SAS. Additionally, classical meta-analytical statistics were also fitted using METAN and METAREG procedures of STATA. The final models included the fixed effects of methods of cryopreservation and random effects of the experiment. Rates (LSM ± SEM) of re-expansion (0.36 ± 0.07 vs. 0.48 ± 0.08), hatching (0.25 ± 0.05 vs. 0.42 ± 0.07), and survival (0.57 ± 0.09 vs. 0.76 ± 0.07) at 72 h post-thawing/warming were lower (P < 0.05) in SF than VF, respectively. The TN of embryonic cells (96.89 ± 7.15 vs. 117.83 ± 7.15) remained lower (P < 0.05) in SF than VF, however, the relative risk (RR) of pregnancy rate post ET remained similar (RR = 1.0, CI = 0.8-1.2; P > 0.05) between both methods. Collectively, VF technique has a short-term protective effect against cryodamage of preimplantation embryos, however, it might be dysregulating genes involved in pregnancy success post ET in cows.

A prospective study of oral estrogen versus transdermal estrogen (gel) for hormone replacement frozen embryo transfer cycles

AIM

This study was done to compare the efficacy of transdermal estrogen (gel) to oral estradiol in hormone replacement frozen embryo transfer cycles (HR- FET).

MATERIALS AND METHODS

This was a prospective study conducted between March 2019 and December 2019. We included 294 HR FET cycles: 156 cycles using oral estrogen tablets (oral group) and 138 cycles using transdermal gel (17 beta estradiol 0.06% w/w) (gel group). Primary objective of this study was to compare endometrial thickness (ET) on the day of progesterone start between the two groups. Our secondary objective was to compare implantation rates (IR), clinical pregnancy rates (CPR), miscarriage rates (MR), duration of estrogen administration, estradiol (E2) levels before the start of progesterone, cycle cancellation rates, patient satisfaction score and undesirable side effects between both the groups.

RESULTS

There was no significant difference in the ET, IR, CPR, MR and duration of E2 administration and cycle cancellation rates between both the groups. Patient satisfaction score was significantly higher (8.02 ± 1.07 vs 6.96 ± 0.99 p < .01) and side effects were significantly lower (18.1% vs 55.1%, p≤.01), in the gel group compared to the oral group.

CONCLUSION

This study concluded that transdermal estrogen (gel) is equally efficacious as oral estrogen in HR FET cycles with transdermal gel having an added benefit of better patient comfort with less side effects and better safety profile.

Conduction Cooling and Plasmonic Heating Dramatically Increase Droplet Vitrification Volumes for Cell Cryopreservation

Droplet vitrification has emerged as a promising ice-free cryopreservation approach to provide a supply chain for off-the-shelf cell products in cell therapy and regenerative medicine applications. Translation of this approach requires the use of low concentration (i.e., low toxicity) permeable cryoprotectant agents (CPA) and high post cryopreservation viability (>90%), thereby demanding fast cooling and warming rates. Unfortunately, with traditional approaches using convective heat transfer, the droplet volumes that can be successfully vitrified and rewarmed are impractically small (i.e., 180 picoliter) for <2.5 m permeable CPA. Herein, a novel approach to achieve 90-95% viability in micro-liter size droplets with 2 m permeable CPA, is presented. Droplets with plasmonic gold nanorods (GNRs) are printed onto a cryogenic copper substrate for improved cooling rates via conduction, while plasmonic laser heating yields >400-fold improvement in warming rates over traditional convective approach. High viability cryopreservation is then demonstrated in a model cell line (human dermal fibroblasts) and an important regenerative medicine cell line (human umbilical cord blood stem cells). This approach opens a new paradigm for cryopreservation and rewarming of dramatically larger volume droplets at lower CPA concentration for cell therapy and other regenerative medicine applications.

Association between serum estradiol levels prior to progesterone administration in artificial frozen-thawed blastocyst transfer cycles and live birth rate: a retrospective study

OBJECTIVE

To study whether serum estradiol (E2) levels prior to progesterone administration in the artificial endometrial preparation (AEP) of frozen-thawed blastocyst transfer affect the live birth rate.

DESIGN

Retrospective cohort study.

SETTING

Tertiary-care academic medical centre.

POPULATION

A total of 3857 frozen-thawed blastocyst transfer cycles were divided into three groups: <200 pg/ml (n = 1676); 200-399 pg/ml (n = 1296); and ≥400 pg/ml (n = 885), based on the 25th (182.3 pg/ml) and 75th percentile (390.2 pg/ml) of serum E2 level prior to progesterone administration.

METHODS

Univariable and multivariable logistic regression analysis was performed.

MAIN OUTCOME MEASURES

The primary outcome of the study was the live birth rate and the secondary outcomes included clinical pregnancy rate, pregnancy loss rate, neonatal birthweight, Z-score, and small for gestational age (SGA).

RESULTS

Compared with the reference group, accounting for major covariates, the live birth rate significantly decreased in the '≥400 pg/ml' group (adjusted OR 0.71, 95% CI 0.59-0.85). Compared with the reference group, there was an association between the E2 level in the '≥400 pg/ml' group and a decrease in the clinical pregnancy rate (adjusted OR 0.74, 95% CI 0.61-0.89). Compared with the reference group, the pregnancy loss rate significantly increased in the '≥400 pg/ml' group (adjusted OR 1.45, 95% CI 1.08-1.93). The E2 levels did not affect neonatal birthweight, Z-score, and SGA among singletons.

CONCLUSIONS

High serum E2 levels prior to progesterone administration in AEP are associated with a decreased live birth rate after frozen-thawed blastocyst transfer.

TWEETABLE ABSTRACT

High serum E2 levels prior to progesterone administration in artificial FET are associated with a decreased live birth rate after frozen-thawed blastocyst transfer.

Comparison of the Method of Endometrial Preparation Prior to Frozen-Thawed Embryo Transfer: a Retrospective Cohort Study from 9733 Cycles

Our objective was to compare the effectiveness of natural cycles (NC), modified natural cycle (mNC), and artificial cycles (AC) in women undergoing frozen-thawed embryo transfer (FET) after in vitro fertilization (IVF). This is a retrospective cohort study analyzing 9733 women undergoing the first cycle of FET over a 3-year period (June 2014-December 2017) at Northwest Women's and Children's Hospital after IVF-ICSI cycles. The type of endometrial preparation was determined by the treating physician's preference, based on patients' characteristics. Women with regular ovulation were allocated to natural cycles (n = 1480) or modified natural cycles (n = 196) when the leading follicle was triggered with hCG, while patients who were reluctant to frequently monitoring or living far from the hospital were allocated to artificial cycles (n = 8057). A logistic regression model was used to assess the association between endometrial preparation and clinical outcomes while adjusting for potential confounders. Live birth rate was primary outcome while miscarriage rate, clinical pregnancy rate, preterm birth rate, and ectopic pregnancy rate were secondary outcomes. In the adjusted model, type of endometrial preparation did not affect live birth (OR, 0.89; 95% CI, 0.74-0.96), clinical pregnancy (OR, 0.93; 95% CI, 0.81-1.06), preterm birth (OR, 1.03; 95% CI, 0.84-1.26), and ectopic pregnancy (OR, 0.73; 95% CI, 0.33-1.59), while AC significantly increased the miscarriage rate (OR, 1.49; 95% CI, 1.17-1.89, P=0.001). In conclusions, in women undergoing FET, natural cycles and artificial cycles resulted in comparable live birth rate while miscarriage rate was higher in artificial cycles.

The effect of storage time after vitrification on pregnancy and neonatal outcomes among 24 698 patients following the first embryo transfer cycles

STUDY QUESTION

To evaluate the impact of storage time after vitrification on embryo viability, pregnancy outcomes and neonatal outcomes.

SUMMARY ANSWER

The prolonged storage time of vitrified embryos negatively affected pregnancy outcomes, including biochemical pregnancy rate, clinical pregnancy and live birth rate; but did not influence neonatal outcomes.

WHAT IS KNOWN ALREADY

Although vitrification has been the fundamental tool of ART treatments in recent years, few studies have explored the influence of storage period after vitrification on embryonic and clinical outcomes.

STUDY DESIGN, SIZE, DURATION

A retrospective study was performed among 24 698 patients with the first vitrified embryo transfer following a freeze-all strategy during the period from January 2011 to December 2017.

PARTICIPANTS/MATERIAL, SETTING, METHODS

A total of 24 698 patients met the inclusion criteria and were grouped according to the storage time (11 330 patients in Group 1 with storage time <3 months, 9614 patients in Group 2 with storage time between 3 and 6 months, 3188 patients in Group 3 with storage time between 6 and 12 months and 566 in Group 4 with storage time between 12 and 24 months). The pregnancy outcomes and neonatal outcomes were compared between different storage time groups. Multivariate logistic regression and linear regression were performed to evaluate the independent effect of storage time on clinical outcomes, adjusting for important confounders.

MAIN RESULTS AND THE ROLE OF CHANCE

After adjustment for potential confounding factors, the chance of biochemical pregnancy (Group 1 as reference; Group 2: adjusted odds ratio (aOR) = 0.92, 95% CI 0.87-0.97; Group 3: aOR = 0.83, 95% CI 0.76-0.90; Group 4: aOR = 0.68, 95% CI 0.56-0.81), clinical pregnancy (Group 2: aOR = 0.91, 95% CI 0.86-0.96; Group 3: aOR = 0.80, 95% CI 0.73-0.87; Group 4: aOR = 0.65, 95% CI 0.54-0.79) and live birth (Group 2: aOR = 0.89, 95% CI 0.85-0.95; Group 3: aOR = 0.83, 95% CI 0.76-0.91; Group 4: aOR = 0.59, 95% CI 0.48-0.72) significantly decreased with the increasing storage time, whereas the relationship between miscarriage, ectopic pregnancy and storage time did not reach statistical significance. In addition, there was no evidence of differences in adverse neonatal outcomes (preterm birth, low birthweight, high birthweight, macrosomia or birth defects) between groups.

LIMITATION, REASONS FOR CAUTION

Our study was limited by the retrospective design from a single center, the conclusion from our study needs to be verified in further studies.

WIDER IMPLICATIONS OF THE FINDINGS

This study provides new findings about the relationship between prolonged storage time of vitrified embryos and clinical outcomes and offers evidence for the safety of using long-stored embryos after vitrification.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the National Natural Science Foundation of China (grant nos. 81903324, 81771533, 81571397, 81701523), National Key Research and Development Program of China (grant no. SQ2018YFC100163). None of the authors have any conflicts of interest to declare.

Live birth and clinical outcome of vitrification-warming donor oocyte programme: an experience of a single IVF unit

Medically assisted reproductive (MAR) treatments using donated oocytes are commonly applied in several countries to treat women who cannot conceive with their own gametes. Historically, in Italy, gamete donation has been prohibited but, in 2014, the law changed and gamete donation became allowed for couples undergoing MAR treatments. Consequently, in the last decade, there has been an increase in application of the oocyte donation programme. This study reports an egg-donation programme's clinical efficacy, based on importing donated vitrified oocytes from cryo-banks located in a foreign country. For this, we conducted a retrospective analysis of data from a single reproductive unit located in Italy (Donna Salus Women's Health and Fertility, Bozen). The study group consisted of 681 vitrified oocytes, which were warmed and culture to be replaced in 100 recipients. The survival rate after warming was 79.1% (n = 539/681), whereas the fertilization and blastulation rates were 90.2% (n = 486/539) and 47.9% (n = 233/486), respectively. Positive pregnancy test, clinical pregnancy rates, and live-birth rates per embryo transfer were 37.8%, 31.1% and 28.4%, respectively. The multiple pregnancy rate was 0.7%. This study is one of the first to report on the efficacy of a donor oocyte programme in Italy using imported vitrified oocytes. The above data may reassure women who are undertaking donation programmes using vitrified oocytes imported from commercial egg banks.

Winter is coming: the future of cryopreservation

The preservative effects of low temperature on biological materials have been long recognised, and cryopreservation is now widely used in biomedicine, including in organ transplantation, regenerative medicine and drug discovery. The lack of organs for transplantation constitutes a major medical challenge, stemming largely from the inability to preserve donated organs until a suitable recipient is found. Here, we review the latest cryopreservation methods and applications. We describe the main challenges-scaling up to large volumes and complex tissues, preventing ice formation and mitigating cryoprotectant toxicity-discuss advantages and disadvantages of current methods and outline prospects for the future of the field.

Storage Time of Cryopreserved Embryos and Pregnancy Outcomes: A Dose-Response Meta-Analysis

Purpose Cryopreservation techniques have become an essential part of assisted reproduction technology. Embryos may be cryopreserved for several years before transfer, and the safety of long-term cryopreservation needs to be considered. This dose-response meta-analysis was conducted to evaluate whether there were dose-response relationships between the storage time of cryopreserved embryos and pregnancy outcomes such as survival rate, implantation rate, miscarriage rate, clinical pregnancy rate, and congenital malformation rate. Methods After searching the databases PubMed, Embase, MEDLINE, CCRT and related reviews up until June 4, 2020, seven studies were included for analysis. Two reviewers extracted the relevant information and independently assessed the study quality using the Newcastle-Ottawa scale. Potential linear or non-linear dose-response relationships were assessed with a random-effect dose-response meta-analysis. Results No dose-response association was found between duration of embryo cryostorage and survival rate, implantation rate, miscarriage rate, clinical pregnancy rate or congenital malformation rate. Conclusion The interval between the start of embryo cryopreservation and frozen/thawed embryo transfer does not influence pregnancy outcomes.

Comparative study between two techniques for artificial shrinkage of blastocysts prior to vitrification: LASER pulse versus micro-needle technique in increasing chemical, clinical pregnancy and live birth rates after ICSI, a randomized controlled trial

PURPOSE

This work investigates ICSI outcome between LASER Artificial Shrinkage (LAS) and Micro-Needle Artificial Shrinkage (MNAS) before vitrification.

PATIENTS AND METHODS

Four hundred and nine women were included in the study; which were randomly divided into two groups according to the technique used for artificial shrinkage step of the blastocyst before vitrification: in the first group, Laser beam was used while in the second group the micro-needle was used. Ovarian stimulation was done before the ICSI procedure either by long, short or antagonist protocol.

RESULTS

The statistical analysis of our study revealed that there was no statistically significant difference between the two groups regarding age, number of cases, AMH, Basal FSH, BMI, male factor, usage ovarian stimulation protocol, high quality blastocysts, the mean number of transferred embryos. While, there was a statistically significant difference between two groups after thawing with p-value < .001 in favor of the LAS method regarding the morphology of originally high quality blastocysts, blastocysts healthiness (not degenerated), pregnancy rate, the implantation rates.

CONCLUSION

LASER artificial shrinkage of human blastocysts is a promising technology that could be implemented on a wider basis to improve ART practice, as our study revealed that the usage of LASER pulse for artificial shrinkage of blastocysts before vitrification has better implantation rate as well as better chemical and clinical pregnancy rate in comparison to the usage of micro-needle artificial shrinkage of blastocysts before vitrification. There is a statistically significant difference regarding live birth rate being more in the LASER group as compared to needle group, also the number of twins ether identical or non-identical are larger in laser group than in needle group but with no statistically significant difference. Clinical trials.gov ID: NCT04125017.

Risk of neurodevelopmental disorders in children born from different ART treatments: a systematic review and meta-analysis

BACKGROUND

Various techniques in assisted reproductive technology (ART) have been developed as solutions for specific infertility problems. It is important to gain consensual conclusions on the actual risks of neurodevelopmental disorders among children who are born from ART. This study aimed to quantify the relative risks of cerebral palsy, intellectual disability, autism spectrum disorder (ASD), and behavioral problems in children from different ART methods by using systematic review and meta-analysis. Healthcare providers could use the results of this study to suggest the suitable ART technique and plan optimum postnatal care.

METHODS

Pubmed, Google Scholar, and Scopus databases were used to search for studies up to January 2020. Of the 181 screened full manuscripts, 17 studies (9.39%) fulfilled the selection criteria. Based on the Newcastle-Ottawa scale ratings, 7 studies were excluded, resulting in 10 studies that were eventually included in the meta-analyses. Mantel-Haenszel risk ratio model was used in the meta-analysis, and the results are described using forest plot with 95% confidence interval. Heterogeneity was assessed using the I² value.

RESULTS

Pooled evaluation of 10 studies showed that the risk of cerebral palsy in children from assisted reproductive technology (ART) is higher than children from natural conceptions (risk ratio [RR] 1.82, [1.41, 2.34]; P = 0.00001). Risk of intellectual disability (RR 1.46, [1.03, 2.08]; P = 0.03) and ASD (RR 1.49 [1.05, 2.11]; P = 0.03) are higher in intracytoplasmic sperm injection (ICSI) children compared to conventional in vitro fertilization (IVF) children. The differences in the risk of neurodevelopmental disorders in children born after frozen and fresh embryo transfers are not significant. Analysis on potential cofounder effects, including multiple birth, preterm birth, and low birth body weight highlight possibilities of significant correlation to the risks of neurodevelopmental disorders.

CONCLUSIONS

Pooled estimates suggest that children born after ART are at higher risk of acquiring cerebral palsy. ICSI treatment causes higher risk of intellectual disability and ASD. These findings suggest the importance of the availability of intensive care unit at the time of delivery and long-term developmental evaluation particularly in children from ICSI.

Gene expression changes in response to low temperatures in embryos of the kelp grouper, Epinephelus moara

The kelp grouper Epinephelus moara has high economic value and is popular in fisheries and aquaculture in China. In the previous study, we treated the embryos at 16-22 somite stage at 4 °C, -25.7 °C, -140 °C and -196 °C, and successfully obtained surviving embryos in each group. To better understand the molecular changes affected by the low temperatures, we conducted a comparative transcriptome analysis among embryos exposed at 4 °C for 30 min, embryos exposed at -25.7 °C for 30 min and the control group. qPCR assays were conducted for the validation. Signal transduction pathways were highly enriched for the differentially expressed genes. c-Fos, c-Jun, JunD, GADD45, involved in MAPK signaling pathway, were upregulated when embryos were treated at low temperatures. As immediate early genes, Egr-1a and b, and IER2, that respond quickly to the environment stress, their expression increased as well. Hsp70 showed similar expression pattern as immediate early genes. Meanwhile, transcription factors Sox, HES, TFIID, muscle movement and protein synthesis-related genes were downregulated. Taken together, our findings suggest that cooling disrupts gene expression patterns in E. moara embryos. The differentially expressed genes may be involved in cellular resistance against low temperatures, possibly through neural activation, apoptosis, proliferation, differentiation, cellular recovery and heat shock regulation. This study also provides transcriptome dataset of E. moara embryos exposed to cold temperatures for future studies focusing on the molecular effects of cryopreservation.

Is there an optimal number of oocytes retrieved at which live birth rates or cumulative live birth rates per aspiration are maximized after ART? A systematic review

The association between the number of oocytes retrieved and fresh live birth rate (LBR) or cumulative LBR (CLBR), and whether an optimal number of oocytes are retrieved when LBR or CLBR are maximized, are highly relevant clinical questions; however published results are conflicting. A systematic review of all eligible studies (n = 16) published until January 2020 on MEDLINE, Embase, Scopus, CINAHL and Web of Science was conducted. Five studies evaluated only LBR from fresh cycles, five studies evaluated only CLBR from stimulated cycles and six evaluated both. A marked difference was observed between the oocyte yields at which LBR and CLBR were reportedly maximized in the individual studies. On the basis of nine studies, the optimal number of oocytes at which fresh LBR seems to be maximized is proposed to be between 12 and 18 oocytes (15 oocytes was the most common suggestion). On the other hand, CLBR continues to increase with the number of oocytes retrieved. This is the first systematic review on the topic, and it suggests that the retrieval of 12-18 oocytes is associated with maximal fresh LBR, whereas a continuing positive association is present between the number of oocytes retrieved and CLBR.