Vitrification is a highly efficient method to cryopreserve human embryos in in vitro fertilization patients at high risk of developing ovarian hyperstimulation syndrome

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

STUDY QUESTION

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

SUMMARY ANSWER

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

WHAT IS KNOWN ALREADY

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

STUDY DESIGN, SIZE, DURATION

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

PARTICIPANTS/MATERIALS, SETTING, METHODS

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

MAIN RESULTS AND THE ROLE OF CHANCE

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

LIMITATIONS, REASONS FOR CAUTION

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

WIDER IMPLICATIONS OF THE FINDINGS

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

STUDY FUNDING/COMPETING INTEREST(S)

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

TRIAL REGISTRATION NUMBER

N/A.

A Personalized Management Approach of OHSS: Development of a Multiphase Prediction Model and Smartphone-Based App

OBJECTIVE

This study aimed to develop multiphase big-data-based prediction models of ovarian hyperstimulation syndrome (OHSS) and a smartphone app for risk calculation and patients' self-monitoring.

METHODS

Multiphase prediction models were developed from a retrospective cohort database of 21,566 women from January 2017 to December 2020 with controlled ovarian stimulation (COS). There were 17,445 women included in the final data analysis. Women were randomly assigned to either training cohort (n = 12,211) or validation cohort (n = 5,234). Their baseline clinical characteristics, COS-related characteristics, and embryo information were evaluated. The prediction models were divided into four phases: 1) prior to COS, 2) on the day of ovulation trigger, 3) after oocyte retrieval, and 4) prior to embryo transfer. The multiphase prediction models were built with stepwise regression and confirmed with LASSO regression. Internal validations were performed using the validation cohort and were assessed by discrimination and calibration, as well as clinical decision curves. A smartphone-based app "OHSS monitor" was constructed as part of the built-in app of the IVF-aid platform. The app had three modules, risk prediction module, symptom monitoring module, and treatment monitoring module.

RESULTS

The multiphase prediction models were developed with acceptable distinguishing ability to identify OHSS at-risk patients. The C-statistics of the first, second, third, and fourth phases in the training cohort were 0.628 (95% CI 0.598-0.658), 0.715 (95% CI 0.688-0.742), 0.792 (95% CI 0.770-0.815), and 0.814 (95% CI 0.793-0.834), respectively. The calibration plot showed the agreement of predictive and observed risks of OHSS, especially at the third- and fourth-phase prediction models in both training and validation cohorts. The net clinical benefits of the multiphase prediction models were also confirmed with a clinical decision curve. A smartphone-based app was constructed as a risk calculator based on the multiphase prediction models, and also as a self-monitoring tool for patients at risk.

CONCLUSIONS

We have built multiphase prediction models based on big data and constructed a user-friendly smartphone-based app for the personalized management of women at risk of moderate/severe OHSS. The multiphase prediction models and user-friendly app can be readily used in clinical practice for clinical decision-support and self-management of patients.

Whether Letrozole could reduce the incidence of early ovary hyperstimulation syndrome after assisted reproductive technology? A systematic review and meta-analysis

Background

Letrozole can significantly decrease the estrogen level, and has been administrated to prevent the incidence of early ovary hyperstimulation syndrome (OHSS). However, the effect of Letrozole on prevention of OHSS reached to controversial conclusions. The present meta-analysis aim to examine whether Letrozole could reduce the incidence of early OHSS after assisted reproductive technology (ART).

Methods

An exhaustive electronic literature search was conducted on MEDLINE, Google Scholar, CNKI and WANFANG MED ONLINE, from inception until May 2018. We include clinical trials that examined the effect of Letrozole on the prevention of early OHSS. The main outcome measures were the incidence of total early OHSS, mild early OHSS, moderate early OHSS, and severe early OHSS.

Results

Eight studies included in the review. Of these, five publications evaluated the effect of Letrozolel on the prevention of total, mild, moderate, and severe OHSS, respectively. The results indicated that there was a significantly decreased incidence of total OHSS with Letrozole compared with control group, and there were no significantly differences in the incidence of mild, moderate, and severe OHSS between study group with Letrozole and control group. Eight studies reported the incidence of moderate + severe OHSS. We found a significant decrease in incidence of moderate + severe OHSS in high-risk women with Letrozole.

Conclusions

Letrozole has no beneficial effect on the prevention of mild, moderate, and severe OHSS, individually; Letrozole should not be considered as the first-line treatment for prevention of OHSS. Further cohort studies are required to explore the effect of Letrozole on the prevention of OHSS.

Plain English Summary

This study aimed to examine whether Letrozole could reduce the incidence of early OHSS after assisted reproductive technology (ART). A meta-analysis including 8 studies was conducted. There were no significantly differences in the incidence of mild, moderate, and severe OHSS between study group with Letrozole and control group. Letrozole has no beneficial effect on the prevention of mild, moderate, and severe OHSS, individually.

Testing the efficacy and efficiency of a single "universal warming protocol" for vitrified human embryos: prospective randomized controlled trial and retrospective longitudinal cohort study

Purpose

To study the efficacy and efficiency of a “universal warming protocol” for vitrified human embryos, based on subsequent steps with 1 and 0.5 M concentration of extracellular cryoprotectant (ECCP).

Method

Two studies on patients undergoing fertility treatments via ICSI: a prospective randomized controlled trial (RCT) and a retrospective cohort study (CS). Setting: Private assisted reproductive (AR) center.

RCT: duration 01/03/2017–01/10/2017; 315 embryos at blastocyst stage obtained from 169 patients. Each patient’s embryos were first randomized for vitrification with two different kits: Vitrification Kit (Kitazato, Japan) and Sage Vitrification Kit (Origio, Denmark). The embryos were randomly warmed with either Kitazato (K) or Sage (S) warming kits, specifically: group A (KK), group B (KS), group C (SK), and group D (SS). Primary outcome measure: survival rate (number of embryos surviving per number of embryos warmed). Secondary: implantation rate (number of embryos implanted per number of embryos transferred).

CS: duration 01/01/2013–31/12/2015 embryos from patients’ own oocytes; 10/04/2015–31/07/2017 embryos from donors’ oocytes. A total of 1055 embryos vitrified at cleavage stage obtained from 631 warming cycles: 847 of these obtained from patients’ own oocytes, 208 egg-donation-derived embryos. Each patient’s embryos were vitrified and warmed in various combinations of three different vitrification/warming kits: Kitazato (K), Sage (S), or made in-house in our laboratory (H). Vitrification/warming kits from different manufacturers are routinely used in our AR center, and the warming procedures are randomly performed with any available kit on a “first-in-first-out” basis, irrespective of the kit used for vitrification. Group names: KK, KS, SK, SS, SH, HK, HS, HH (embryos from patients’ own oocytes); eKK, eKS, eSK, eSS (egg-donation-derived embryos).

Results

Cryo-survival rates were comparable in all study groups.

RCT. Group A 99.0% (96/97), group B 98.8% (83/84), group C 98.4% (61/62), and group D 98.6% (71/72).

CS. Embryos from patients’ own oocytes: KK 96.4% (54/56), KS 100.0% (13/13), SK 98.8% (80/81), SS 97.2% (174/179), SH 97.6% (40/41), HK 95.2% (20/21), HS 99.5% (187/188), and HH 97.4% (261/268). Egg-donation-derived embryos: eKK 100.0% (91/91), eKS 98.4% (60/61), eSK 100.0% (26/26), and eSS 96.7 (29/30).

Implantation was generally comparable in all study groups—exceptions were in CS: KS vs. SK (P = 0.049), SS (P = 0.012), HS (P = 0.010), HH (P = 0.025); and SH vs. SS (P = 0.042), HS (P = 0.035).

Conclusion

Worldwide, millions of embryos have been cryopreserved using different vitrification kits; these studies establish that it is possible to combine different kits for vitrification and warming using a universal warming protocol. This can optimize costs, simplify lab routines, and favor embryo exchange between IVF centers.

RCT registration number

ISRCTN12342851.

Cryopreserved embryo transfer: adjacent or non-adjacent to failed fresh long GnRH-agonist protocol IVF cycle

The optimal time to perform cryopreserved embryo transfer (CET) after a failed oocyte retrieval-embryo transfer (OR-ET) cycle is unknown. Similar clinical pregnancy rates were recently reported in immediate and delayed CET, performed after failed fresh OR-ET, in cycles with the gonadotrophin-releasing hormone (GnRH) antagonist protocol. This study compared outcomes of CET performed adjacently (<50 days, n = 67) and non-adjacently (≥50 to 120 days, n = 62) to the last OR-day of cycles with the GnRH agonist down-regulation protocol. Additional inclusion criteria were patients' age 20-38 years, the transfer of only 1-2 cryopreserved embryos, one treatment cycle per patient and artificial preparation for CET. Significantly higher implantation, clinical pregnancy and live birth rates were found in the non-adjacent group than in the adjacent group: 30.5% versus 11.3% (P = 0.001), 41.9% versus 17.9% (P = 0.003) and 32.3% versus 13.4% (P = 0.01), respectively. These results support the postponement of CET after a failed OR-ET for at least one menstrual cycle, when a preceding long GnRH-agonist protocol is used.

Shortened equilibration time can compromise clinical outcomes in human embryo vitrification

Vitrification is an important way to cryopreserve human embryos and the recommended time of embryo exposure to the vitrification solution is 1 min. However, practically speaking, the duration of embryos exposure to equilibration solution can vary from 5 to 15 min. The purpose of this study was to investigate the effect of different equilibration times on the outcomes of frozen-thawed embryo transfer cycles. The data were collected from our medical records from January 2012 to June 2013 and a total of 517 cycles were included. These cycles were divided into four groups according to the equilibration time: (i) 5-6 min; (ii) 7-8 min; (iii) 9-10 min and (iv) 11-12 min. The results show that there were no differences in terms of survival rate and fully intact embryo rate among the four groups. However, lower clinical pregnancy, embryo implantation and live birth rates were observed in the 5-6 min exposure group (54.6%, 31.9% and 48.2%, respectively) compared with the three other groups. The corresponding rates in the 9-10 min group (73.5%, 47.6% and 64.7%) were the highest. This study indicated that different equilibration times influenced the clinical outcomes of human embryo vitrification and vitrification with shortened equilibration time compromised the clinical outcomes. Appropriate prolongation of the equilibrium time would probably improve the clinical outcomes.

Vitrification in human and domestic animal embryology: work in progress

According to the analysis of papers published in major international journals, rapidly increasing application of vitrification is one of the greatest achievements in domestic animal and especially human embryology during the first decade of our century. This review highlights factors supporting or hampering this progress, summarises results achieved with vitrification and outlines future tasks to fully exploit the benefits of this amazing approach that has changed or will change many aspects of laboratory (and also clinical) embryology. Supporting factors include the simplicity, cost efficiency and convincing success of vitrification compared with other approaches in all species and developmental stages in mammalian embryology, while causes that slow down the progress are mostly of human origin: inadequate tools and solutions, superficial teaching, improper application and unjustified concerns resulting in legal restrictions. Elimination of these hindrances seems to be a slower process and more demanding task than meeting the biological challenge. A key element of future progress will be to pass the pioneer age, establish a consensus regarding biosafety requirements, outline the indispensable features of a standard approach and design fully-automated vitrification machines executing all phases of the procedure, including equilibration, cooling, warming and dilution steps.

Predicting and preventing ovarian hyperstimulation syndrome (OHSS): the need for individualized not standardized treatment

Ovarian hyperstimulation syndrome (OHSS) is the most serious complication of controlled ovarian stimulation (COS) as part of assisted reproductive technologies (ART). While the safety and efficacy of ART is well established, physicians should always be aware of the risk of OHSS in patients undergoing COS, as it can be fatal. This article will briefly present the pathophysiology of OHSS, including the key role of vascular endothelial growth factor (VEGF), to provide the foundation for an overview of current techniques for the prevention of OHSS. Risk factors and predictive factors for OHSS will be presented, as recognizing these risk factors and individualizing the COS protocol appropriately is the key to the primary prevention of OHSS, as the benefits and risks of each COS strategy vary among individuals. Individualized COS (iCOS) could effectively eradicate OHSS, and the identification of hormonal, functional and genetic markers of ovarian response will facilitate iCOS. However, if iCOS is not properly applied, various preventive measures can be instituted once COS has begun, including cancelling the cycle, coasting, individualizing the human chorionic gonadotropin trigger dose or using a gonadotropin-releasing hormone (GnRH) agonist (for those using a GnRH antagonist protocol), the use of intravenous fluids at the time of oocyte retrieval, and cryopreserving/vitrifying all embryos for subsequent transfer in an unstimulated cycle. Some of these techniques have been widely adopted, despite the scarcity of data from randomized clinical trials to support their use.

A comparison of live birth rates and cumulative ongoing pregnancy rates between Europe and North America after ovarian stimulation with corifollitropin alfa or recombinant follicle-stimulating hormone

OBJECTIVE

To compare live birth rates after fresh embryo transfer (ET) and cumulative ongoing pregnancy rates after fresh ET and frozen-thawed (ET) between continents and overall after one treatment cycle with corifollitropin alfa or recombinant FSH.

DESIGN

Double-blind, multicenter, randomized controlled trial.

SETTING

Fourteen centers in North America (NA); 20 in Europe (EU).

PATIENT(S)

804 NA patients and 702 EU patients.

INTERVENTION(S)

Patients >60 kg received a single dose of corifollitropin alfa or daily rFSH for the first 7 days of controlled ovarian stimulation.

MAIN OUTCOME MEASURE(S)

Live birth rates.

RESULT(S)

Within each continent no differences were noted between the two treatment groups; however, between continents, the cumulative ongoing pregnancy rate and live birth rate were considerably higher in NA than in EU. The live birth rate in NA was 39.2% in both treatment groups compared with 31.5% and 28.8% in EU after corifollitropin alfa and rFSH treatment, respectively. Considering the number of embryos transferred, the live birth rate per ET was still higher in NA than in EU (42.7% v.s 36.8% with corifollitropin alfa and 41.6% vs. 30.9% with rFSH). Overall live birth rates after fresh ET were 35.6% and 34.4% (estimated difference 1.1% [95% confidence interval -3.7-5.8]), and the estimated cumulative live birth rates were 43.4% and 41.3% with corifollitropin alfa and rFSH, respectively.

CONCLUSION(S)

Live birth rates and cumulative pregnancy rates were higher in NA than in EU after treatment with either corifollitropin alfa or daily rFSH; both treatment protocols provided equal success rates. CLINICALTRIALS.GOV IDENTIFIERS: NCT00703014 and NCT00702273.

Successful in vitro culture of pre-antral follicles derived from vitrified murine ovarian tissue: oocyte maturation, fertilization, and live births

Cryopreservation of ovarian tissue is an important option for preserving the fertility of cancer patients undergoing chemotherapy and radiotherapy. In this study, we examined the viability and function of oocytes derived in vitro from pre-antral follicles as an alternative method for restoring fertility. Pre-antral follicles (specified as secondary follicle with a diameter around 100-130 μm) were mechanically isolated from vitrified-warmed and fresh adult mouse ovarian tissues and cultured for 12 days followed by an ovulation induction protocol at the end of this period to initiate oocyte maturation. Oocytes were then released from these follicles, fertilized in vitro, and cultured to the blastocyst stage and vitrified. After storage in liquid nitrogen for 2 weeks, groups of vitrified blastocysts were warmed and transferred into pseudo-pregnant recipient females. Although most of the isolated mouse pre-antral follicles from fresh (79.4%) and vitrified (75.0%) ovarian tissues survived the 12-day in vitro culture period, significantly fewer mature oocytes developed from vitrified-warmed pre-antral follicles than from the fresh controls (62.2 vs 86.4%, P<0.05). No difference was observed in embryo cleavage rates between these two groups, but the proportion of embryos that developed into blastocysts in the vitrification group was only half that of the controls (24.2 vs 47.2%, P<0.05). Nevertheless, live births of healthy normal pups were achieved after transfer of vitrified blastocysts derived from both experimental groups. This study shows that successful production of healthy offspring using an in vitro follicle culture system is feasible, and suggests that this procedure could be used in cancer patients who wish to preserve their fertility using ovarian tissue cryopreservation.

Human cleavage-stage embryo vitrification is comparable to slow-rate cryopreservation in cycles of assisted reproduction

OBJECTIVES

To compare embryo survival, pregnancy and implantation rates after cryopreservation of human cleavage-stage embryos with slow-rate cryopreservation or vitrification.

STUDY DESIGN

262 patients, attending for assisted reproduction, were prepared for oocyte retrieval using standard controlled ovarian hyperstimulation protocols. Excess embryos were cryopreserved on day 3 either by vitrification, or slow-rate cryopreservation in a programmable freezer. Cycles of thawing were monitored for thaw efficiency, pregnancy and implantation rates.

RESULTS

Clinical pregnancy and implantation rates were highly comparable between cycles in which day 3 embryos were thawed either after slow-rate cryopreservation or vitrification.

CONCLUSIONS

These data suggest that vitrification of human embryos during assisted reproduction cycles achieves comparable success rates to fresh cycles and therefore can be applied in the laboratory of assisted reproduction.