P-212 Impact of post-thaw blastocyst culture time prior to transfer on live birth rate in frozen-thawed embryo transfer cycles: a retrospective observational study

Study question

Does post-thaw blastocyst culture time prior to transfer influence the live birth rate in frozen-thawed embryo transfer cycles?

Summary answer

Our study revealed that different culture times of frozen-thawed blastocysts prior to transfer does not influence live birth rate.

What is known already

Several studies demonstrated a significantly increased clinical pregnancy rate after a frozen-thawed embryo transfer (FET) compared to a fresh embryo transfer (ET). FET reduces the risk of ovarian hyperstimulation syndrome without facing adverse effects of supraphysiological hormonal levels over endometrial receptivity. However, little is known on the effect of post-thaw embryo culture duration prior to transfer on live birth rate in FET cycles. Recent findings described an improved blastocyst morphological grade after a 20-22h post-thaw culture. Of note, the overnight culture of non-ideal morphology thawed blastocysts prior to transfer resulted in an enhanced live birth rate.

Study design, size, duration

We compared the live birth rate of patients undergoing FET after a short blastocyst culture time (2-4h) prior to transfer to that of patients in whom thawed blastocysts were transferred after a long embryo culture time (20-22h). Frozen-thawed transfers of blastocysts vitrified at Day 5 and subsequently thawed were evaluated. Only transfers of single blastocyst were included.

Participants/materials, setting, methods

The study was conducted at the Infertility Center – Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan. We included couples with indications for IVF cycles who underwent frozen-thawed blastocyst transfer procedure on the following natural cycles for freeze-all strategy or to transfer supernumerary embryos from 2014-2021. Data were analyzed using SPSS Statistics software. We evaluated statistically significant differences using various tests including Fisher's test, chi-squared test and Wilcoxon's test.

Main results and the role of chance

A total of 2012 frozen-thawed cycles were included in the analysis; in 977 of them, blastocysts were transferred after a 2-4h post-thaw period and in 1035, blastocysts were transferred after a 20-22h post thaw culture period. The age of the women was comparable (35.4 ± 4.2 and 35.3 ± 4.1; p = 0.5, respectively in the short and long culture period). According to statistical analysis, no significant difference in pregnancy outcomes was found between the two groups. Live birth rate was respectively 40% and 42% ( p = 0.2) in the short and long post-thaw blastocyst culture period prior to transfer.

Limitations, reasons for caution

Our study was limited by the retrospective nature and was performed in a single fertility center. Moreover, only blastocysts vitrified on day 5 were evaluated and findings might not be generalized to day 6 and 7 blastocysts.

Wider implications of the findings

These findings might be useful in the context of the organization of the laboratory workflow. Indeed, the possibility to thaw blastocysts on the day before transfer may represent an advantage in order to avoid an overload of the laboratory procedures during very busy days.

Trial registration number

28_2022

O-222 Surveillance of scientific research integrity in medically assisted reproduction: a systematic review of the retracted literature

Study question

How many retracted papers are there in the medically assisted reproduction (MAR) literature and, more importantly, what are their particulars?

Summary answer

Article retraction within MAR literature is increasing and the most common reasons for retraction are errors in data and duplicate publications.

What is known already

Article retraction accounts for one of the most serious consequences of research misconduct. Articles may be subject to retraction whenever the findings are found to be unreliable, redundant, plagiarised or the authors are found to have performed unethical research or hidden

Trial registration number

N/A

P-760 Monozygotic twin rate among IVF centers: A multicenter analysis of data from 18 Italian units

Study question

Could factors inherent to individual centers, related to local clinical or laboratory variables, play a role in the increased incidence of monozygotic twins in IVF?

Summary answer

The rate of MZT did not significantly vary among IVF centers

What is known already

The risk of monozygotic twins (MZT) is increased in couples undergoing in vitro fertilization (IVF). Several systematic reviews have investigated the possible determinants linked to IVF, but results obtained have been inconclusive. Associations have been identified with the prolonged culture at blastocyst stage and young female age. Conventional IVF compared to ICSI, and assisted hatching emerged as possible additional risk factors, but evidence is controversial. Meta-analyses, however, cannot provide robust evidence because of the difficulty in performing multivariate analyses. Moreover, available investigations were retrospective and involved relatively small sample sizes hampering the quality of the collected data.

Study design, size, duration

This is a multicenter retrospective cohort study using the Italian ART National Registry database and involving the Centers reporting data from individual IVF cycles from 2015 to 2019. Eighteen IVF centers were included with a total of 87,076 IVF cycles reported during the study period. The primary aim of the study was to investigate whether the incidence of MZT differed among centers.

Participants/materials, setting, methods

Only single embryo transfer cycles were considered. Women who had sex-discordant twin deliveries were excluded. MZT rate was calculated as the number of multiple pregnancies out of the total number of clinical pregnancies. A binomial distribution model was used to determine the 95% CI of the frequency of MZT. The rates among centers were deemed heterogeneous if the 95% CI in at least one center did not include the mean MZT rate.

Main results and the role of chance

Ten centers reported data from 2015 to 2019, eight from 2017 to 2019. An analysis of the main characteristics of the centers revealed considerable variability. The total number of clinical pregnancies fulfilling our inclusion criteria were 10,440. Of these, 7 were found to be twin pregnancies with discordant gender and were excluded, leaving 10,433 for data analyses. The number of cases included per center varied between 11 and 2,823. Overall, 162 pregnancies were found to be multiple: 48 ended in a miscarriage, 28 spontaneously reduced to singletons and 86 women delivered two or more newborns. The vast majority were twins (n = 160), one was triplet, and one was quadruplet. Considering the denominator of 10,433 pregnancies, the rate of MZT was thus 1.5% (95%CI: 1.3 - 1.8%). The MZT rate among centers varied between 0% (95%CI: 0.0 - 25.9%) and 3.2% (95%CI: 1.3 - 8.1%). All the 95%CIs of the rates of MZT include the 1.5% common rate, thus rejecting the hypothesis that this incidence significantly differed among centers. Spearman correlations between the rate of MZT and variables associated with individual center policies could not identify any significant association. Even when restricting the analyses only to the largest centers, no association emerged.

Limitations, reasons for caution

Our study was limited by its retrospective nature. Furthermore, some centers provided less than 100 cases for data analysis and were therefore poorly informative. External confirmation from larger registries is therefore required.

Wider implications of the findings

This study provides evidences that the rate of MZT did not differ among IVF centers. Furthermore, no clinical and laboratory variables inherent to individual centers were identified in the determinism of IVF-associated MZT. Further studies are needed to identify the causes of increased risk of MZT in IVF practice.

Trial registration number

not applicable

Age-related miRNome landscape of cumulus oophorus cells during controlled ovarian stimulation protocols in IVF cycles

STUDY QUESTION

Is the microRNA (miRNA) expression pattern of cumulus oophorus cells (COCs) in women undergoing medically assisted reproduction (MAR) procedures differentially modulated according to patient age and gonadotropin treatment strategy?

SUMMARY ANSWER

Maternal age is an independent factor impacting miRNA expression in COCs while gonadotropin treatment may affect follicular miRNA expression and IVF efficacy.

WHAT IS KNOWN ALREADY

Epigenetic mechanisms in female infertility are complex and poorly studied. DNA methylation, histone modifications, miRNAs and nucleosome positioning influence cellular machinery through positive and negative feedback mechanisms either alone or interactively. miRNAs are important regulators during oogenesis, spermatogenesis and early embryogenesis, and are reported to play a role in regulating crosstalk between the oocyte and COCs. Although miRNome analysis has been performed in female human reproductive tissues (endometrium, myometrium, cervix and ovaries), epigenetic modifications in women with infertility have not been explored in detail. In addition, the impact of gonadotropin treatments during MAR on miRNA expression in COCs has not been fully investigated.

STUDY DESIGN, SIZE, DURATION

This study was carried out in 53 COC samples obtained from mature metaphase II (MII) oocytes in 53 women undergoing MAR treatment. A total of 38 samples for assay development were pooled by maternal age and gonadotropin treatment into four predetermined subgroups: ≥36 years and recombinant human FSH (r-hFSH), n = 10; ≥36 years and r-hFSH+ recombinant human-luteinizing hormone (r-hLH), n = 10; ≤35 years and r-hFSH, n = 9; ≤35 years and r-hFSH+r-hLH, n = 9. miRNome profiles were determined and compared between subgroups. Expression of defined miRNAs was validated in the remaining fifteen samples, representative of each subgroup, by quantitative polymerase chain reaction (PCR).

PARTICIPANTS/MATERIALS, SETTING, METHODS

COCs were processed for miRNA-enriched total RNA extraction and pooled in homogeneous subgroups to obtain a sufficient amount and quality of starting material to perform the analysis. Each pooled sample underwent miRNA profiling using PCR assay system to examine expression of 752 human miRNAs without pre-amplification. Data were analyzed using the delta-delta Ct method for relative quantitation and prediction of target genes (with at least four algorithms predicting the same miRNA-gene interaction pair (HIT)>4). The miRSystem database provided functional annotation enrichment (raw P-value <0.05) of co-expressed miRNAs.

MAIN RESULTS AND THE ROLE OF CHANCE

We found distinctive miRNA expression profiles in each subgroup correlating with age and MAR stimulation. In addition, a number of selective and co-expressed miRNAs were revealed by comparative analysis. A cluster of 37 miRNAs were commonly but differentially expressed in all four pools. Significant differences were observed in expression regulation of 37 miRNAs between age groups (≤35 or ≥36) in women receiving r-hFSH+r-hLH compared to those receiving r-hFSH alone. Higher concentrations and increased numbers of miRNAs were recorded in younger than in older patients, regardless of treatment. Functional and expression studies performed to retrieve common miRNome profiles revealed an enrichment of biological functions in oocyte growth and maturation, embryo development, steroidogenesis, ovarian hyperstimulation, apoptosis and cell survival, glucagon and lipid metabolism, and cell trafficking. The highest scored pathways of target genes of the 37 common miRNAs were associated with mitogen-activated protein kinase (MAPK) signaling pathways, G alpha signaling, transcription regulation, tight junctions, RNA polymerase I and III, and mitochondrial transcription. We identified a potential age- and MAR stimulation-dependent signature in the miRNA landscape of COCs.

LIMITATIONS, REASONS FOR CAUTION

We cannot rule out the possibility that other unknown individual genetic or clinical factors may have interfered with the reported results. Since miRNA profiling was conducted with a predefined array of target probes, other miRNA molecules, potentially modulated by age and hormonal stimulation, may have been missed in this study.

WIDER IMPLICATIONS OF THE FINDINGS

miRNA expression in COCs is modulated by gonadotropin treatment and correlates strongly with age. A better understanding of the expression patterns and functions of miRNAs may lead to the development of novel therapeutics to treat ovarian dysfunction and improve fertility in older women.

STUDY FUNDING/COMPETING INTEREST

This study was funded by Merck KGaA, Darmstadt, Germany. All authors declared no competing interest, except SL and TD who are fully employed by Merck KGaA.

TRIAL REGISTRATION NUMBER

N/A