Antifreeze Protein Supplementation During the Warming of Vitrified Bovine Ovarian Tissue Can Improve the Ovarian Tissue Quality After Xenotransplantation

The occurrence of ice crystallization during ovarian tissue (OT) cryopreservation causes unavoidable cryodamage, and ice recrystallization during the warming is more detrimental than ice crystallization. Here, we investigated that antifreeze protein (AFP) treatment during the warming procedure can improve the bovine OT quality after xenotransplantation (XT). Bovine OTs (n=120) were evenly assigned to four groups: fresh, vitrified-warmed, vitrified-warmed with 10 mg/mL Leucosporidium ice-binding protein (LeIBP, a type of AFP) (LeIBP-10), and vitrified-warmed with 20 mg/mL LeIBP (LeiBP-20). LeIBPs were added to the first warming solution. Twenty pieces of OTs were assigned to each category. The remaining 10 OTs from each category were assigned to the XT-Fresh control, XT-Vitrified-warmed control, XT-LeIBP-10, and XT-LeIBP-20 groups, respectively, and xenotransplanted to 9-week-old ovariectomized nude mice for one week. LeIBP treatment during the warming step increased morphological follicle normality and decreased apoptotic follicle ratios after vitrification-warming and XT. The XT-vitrified-warmed control group showed significantly reduced microvessel density and increased fibrosis when compared to that of the XT-fresh group. Microvessel density and fibrosis were recovered in both LeIBP treated groups. There was no significant difference between the LeIBP-10 and LeIBP-20 groups in all outcomes. AFP treatment during the warming procedure can prevent OT damage, and improve ovarian follicle morphology and apoptosis in both the vitrified-warmed bovine OT and its graft. After confirmation in a human study, AFPs can potentially be applied to human OT cryopreservation to reduce cryodamage and improve the OT quality.

Successful pregnancy following transmyometrial embryo transfer after robot-assisted radical trachelectomy

Radical trachelectomy is a fertility-preserving alternative to radical hysterectomy in carefully selected young women with early-stage cervical cancer. However, in cases with subsequent severe cervical stenosis, assisted reproductive techniques can be difficult. This is a case report of a 34-year-old patient who underwent robot-assisted radical trachelectomy and cerclage for early-stage (IB2) adenosquamous carcinoma. Three months after surgery, the patient underwent ovarian stimulation using a gonadotropin-releasing hormone antagonist protocol. As it was impossible to perform transcervical embryo transfer due to the almost complete absence of the cervical opening, transmyometrial embryo transfer under ultrasound guidance was performed. This resulted in a successful singleton pregnancy. This is the first case of successful pregnancy conceived by in vitro fertilization with transmyometrial embryo transfer in a patient who had previously undergone robot-assisted radical trachelectomy.

The Largest Uterine Leiomyoma Removed by Robotic-Assisted Laparoscopy in the Late Reproductive Age: A Case Report

Uterine leiomyoma is a very common gynecological tumor in the reproductive years. Recent studies have shown that surgical treatment of uterine leiomyoma using robotic-assisted laparoscopic myomectomy (RALM) is associated with significantly fewer complications, lower estimated blood loss, fewer conversions, and less bleeding than conventional laparoscopic myomectomy. This study reports the case of a giant uterine leiomyoma treated using RALM. A 50-year-old woman was referred to our outpatient clinic with progressive abdominal distension. Ultrasonography and magnetic resonance imaging were performed and showed a markedly enlarged uterus containing a 28-cm uterine myoma. RALM confirmed the 28-cm subserosal myoma on the posterior wall of the uterus. The myoma was enucleated, and the myometrial and serosal defect was repaired with a continuous suture using barbed suture materials. The entire myoma was removed using an electric morcellator. The operation lasted for 190 minutes. The total weight of the removed myoma was 3,262 g, and uterine leiomyoma was pathologically diagnosed. There were no postoperative complications. Although the treatment of huge myomas using RALM is controversial and technically demanding, we successfully performed RALM in a patient with a large myoma. This case confirms the efficiency, reliability, and safety of a robotic-assisted laparoscopic approach for removing a huge myoma. In a well-selected case, RALM can be performed by experienced surgeons regardless of the size of fibroids.

Molecular basis of ice-binding and cryopreservation activities of type III antifreeze proteins

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The QAE2ACT and SP ACT mutants showed full TH and IRI activities.

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Active AFPs effectively preserved intact follicle and prevented DSB damage.

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Active AFPs exhibited unique structural feature in the first 3₁₀ helix of the IBS.

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Unique structure of the IBS determines TH, IRI, and cryopreservation activities.

Antifreeze proteins (AFPs) can inhibit the freezing of body fluid at subzero temperatures to promote the survival of various organisms living in polar regions. Type III AFPs are categorized into three subgroups, QAE1, QAE2, and SP isoforms, based on differences in their isoelectric points. We determined the thermal hysteresis (TH), ice recrystallization inhibition (IRI), and cryopreservation activity of three isoforms of the notched-fin eelpout AFP and their mutant constructs and characterized their structural and dynamic features using NMR. The QAE1 isoform is the most active among the three classes of III AFP isoforms, and the mutants of inactive QAE2 and SP isoforms, QAE2^ACT and SP^ACT, displayed the full TH and IRI activities with resepect to QAE1 isoform. Cryopreservation studies using mouse ovarian tissue revealed that the QAE1 isoform and the active mutants, QAE2^ACT and SP^ACT, more effectively preserved intact follicle morphology and prevented DNA double-strand break damage more efficiently than the inactive isoforms. It was also found that all active AFPs, QAE1, QAE2^ACT, and SP^ACT, formed unique H-bonds with the first 3₁₀ helix, an interaction that plays an important role in the formation of anchored clathrate water networks for efficient binding to the primary prism and pyramidal planes of ice crystals, which was disrupted in the inactive isoforms. Our studies provide valuable insights into the molecular mechanism of the TH and IRI activity, as well as the cryopreservation efficiency, of type III AFPs.

A View from the past into our collective future: the oncofertility consortium vision statement

Purpose

Today, male and female adult and pediatric cancer patients, individuals transitioning between gender identities, and other individuals facing health extending but fertility limiting treatments can look forward to a fertile future. This is, in part, due to the work of members associated with the Oncofertility Consortium.

Methods

The Oncofertility Consortium is an international, interdisciplinary initiative originally designed to explore the urgent unmet need associated with the reproductive future of cancer survivors. As the strategies for fertility management were invented, developed or applied, the individuals for who the program offered hope, similarly expanded. As a community of practice, Consortium participants share information in an open and rapid manner to addresses the complex health care and quality-of-life issues of cancer, transgender and other patients. To ensure that the organization remains contemporary to the needs of the community, the field designed a fully inclusive mechanism for strategic planning and here present the findings of this process.

Results

This interprofessional network of medical specialists, scientists, and scholars in the law, medical ethics, religious studies and other disciplines associated with human interventions, explore the relationships between health, disease, survivorship, treatment, gender and reproductive longevity.

Conclusion

The goals are to continually integrate the best science in the service of the needs of patients and build a community of care that is ready for the challenges of the field in the future.

The Significance of Planned Fertility Preservation for Women With Endometrioma Before an Expected Ovarian Cystectomy

Endometrioma is known to reduce the ovarian reserve and the extent of the decrease is more severe when ovarian surgery is performed. Therefore, to prevent this decline in fertility, patients with endometrioma are considered candidates for preoperative fertility preservation (FP). In this study, we evaluate the efficacy of FP in women with endometrioma before planned ovarian surgery. A total of 95 cycles in 62 patients with endometrioma, undergoing controlled ovarian stimulation (COS) for FP using a gonadotropin-releasing hormone (GnRH) antagonist protocol before an expected ovarian surgery, were enrolled retrospectively. COS outcomes were compared according to endometrioma laterality. Additionally, first COS cycle outcomes in patients with endometrioma were compared with those in infertile patients, or in patients with a benign ovarian cyst using propensity score matching. When multiple COS cycles were performed, the results of cumulative cycles were analyzed. Embryo quality was worse in the bilateral endometrioma group. Compared with the infertile patient group, the patients with endometrioma had significantly lower Anti-Müllerian Hormone (AMH) and fewer numbers of oocytes retrieved (median, 3.3 vs. 1.2, p<0.001; 7.0 vs. 4.0, p=0.009, respectively). Compared with mature oocytes in infertile patients or patients with a benign cyst, mature oocytes were fewer in patients with endometrioma, but this was not statistically significant (median, 4.0 vs. 3.0, p=0.085; 5.5 vs. 3.0, p=0.052, respectively). The median value of the cumulative number of cryopreserved oocytes or embryos was 14.5 up to the fourth cycle compared to 3 up to the first cycle, with cumulative effect. Women with endometrioma should be counseled for FP before planned ovarian cystectomy. The number of cryopreserved oocytes or embryos can be increased by repeated cycles.

SARS-CoV-2 and Assisted Reproductive Technology Practice: An Asia Pacific Initiative on Reproduction (ASPIRE) Position Paper

Background: Asia Pacific Initiative on Reproduction (ASPIRE) aims to improve knowledge and awareness of Assisted Reproductive Technology (ART) and infertility-related services, with the aim of improving the quality of patient care.

Methods: A survey was developed and responded by a group of 10 ASPIRE board members to gather in-depth information about current practices, recommendations, and perceptions about SARS-CoV-2 and ART. The collected data were summarized and individual responses pooled among questions requiring voting. The overall rates were computed by response category. The group discussed the summary evidence, until a consensus was reached concerning a series of recommendation on how to make decisions concerning ART service provision during the current (and any future) pandemic. A two-tier recommendation was developed based on agreement rate and implementation priority. Tier 1 comprises recommendations in which the rate of “absolutely agree” responses were [Formula: see text]60%, whereas tier 2 refers to recommendations in which the rate of “absolutely agree” plus “agree” was >60%, but the rate of “absolutely agree” was [Formula: see text]50%.

Results: The survey was responded by all participants between July 24 and July 30, 2020. Nine tier 1 and five tier 2 recommendations are provided concerning prevention, testing, personal protective equipment, informed consent, and quality management. The former indicates the situations in which most individuals should receive the intervention/procedure, whereas the latter relates to those that may be suitable for individual clinics and patients.

Conclusions: This document provides the ASPIRE viewpoint on better managing infertile patients seeking ART during the COVID-19 pandemic. This expert opinion guide aims to help both competent authorities and healthcare providers to deliver quality and safe ART.

Efficacy of dual progesterone administration (intramuscular and vaginal) for luteal support in fresh day 3 or day 4 embryo transfer cycles

Objective

The aim of this study was to compare in vitro fertilization outcomes between fresh day 3 or day 4 embryo transfer cycles with dual progesterone (P) administration (intramuscular and vaginal) and cycles with single intramuscular P administration for luteal support.

Methods

We selected 124 cycles from 100 women (under age 40 years) who underwent oocyte pick-up (number of trials ≤ 3, 4–14 oocytes obtained) and transfer of two or three day 3 or day 4 embryos at two infertility centers from January 2014 to June 2019. Dual P (intramuscular P [50 mg] daily+vaginal P) was used in 52 cycles and a single intramuscular administration of P (50 mg daily) was used in 72 cycles.

Results

Women’s age, infertility factors, number of oocytes retrieved, number of transferred embryos, and mean embryo score were similar between the dual P group and the single P group. Although the number of trial cycles was significantly higher (1.9 vs. 1.5), and the mean endometrial thickness on the trigger day (10.0 mm vs. 11.0 mm) was significantly lower in the dual P group, the implantation rate, clinical pregnancy rate, ongoing pregnancy rate, and miscarriage rate for both day 3 and day 4 transfers were similar between the two groups.

Conclusion

In fresh day 3 or day 4 embryo transfer cycles, dual P administration did not demonstrate any clinical advantages. Intramuscular P alone appears to be sufficient for luteal support.

Association between Platelet-Specific Collagen Receptor Glycoprotein 6 Gene Variants, Selected Biomarkers, and Recurrent Pregnancy Loss in Korean Women

This paper investigates whether glycoprotein 6 (GP6) gene polymorphisms are a risk factor for recurrent pregnancy loss (RPL) in Korean women. Genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism and real-time polymerase chain reaction amplification. We identified five polymorphisms in the GP6 gene: rs1654410 T>C, rs1671153 T>G, rs1654419 G>A, rs12610286 A>G, and rs1654431 G>A. GP6 rs1654410 CC was associated with decreased RPL risk (adjusted odds ratio = 0.292, 95% confidence interval = 0.105–0.815, p = 0.019), and recessive genotypes were also significantly associated with decreased RPL risk (adjusted odds ratio = 0.348, 95% confidence interval = 0.128−0.944, p = 0.038). GP6 rs1654419 GA was associated with decreased RPL risk (adjusted odds ratio = 0.607, 95% confidence interval = 0.375-0.982, p = 0.042), and dominant genotypes were significantly associated with decreased RPL risk (adjusted odds ratio = 0.563, 95% confidence interval = 0.358−0.885, p = 0.013). Altogether, the genotype frequencies of GP6 rs1654410 T>C and GP6 rs1654419 G>A were significantly different between RPL patients and control participants. Therefore, although GP6 polymorphisms may be useful as biomarkers of RPL, additional studies with heterogeneous cohorts are required to better understand the influence of GP6 and assess its performance as a biomarker.

Erratum: Correction of Author ORCID in the Article: Efficacy of Random-start Controlled Ovarian Stimulation in Cancer Patients

This corrects the article on p. 290 in vol. 30, PMID: 25729252.

Effect of luteal phase support with vaginal progesterone on pregnancy outcomes in natural frozen embryo transfer cycles: A meta-analysis

OBJECTIVE

The purpose of this study was to determine the effect of vaginal progesterone for luteal phase support (LPS) on the clinical pregnancy rate (CPR) in natural frozen embryo transfer (FET) cycles via a meta-analysis.

METHODS

We performed a meta-analysis of randomized controlled trials (RCTs) and retrospective studies that met our selection criteria. Four online databases (PubMed, Embase, Medline, and the Cochrane Library) were searched between January 2017 and May 2017. Studies were selected according to predefined inclusion criteria and meta-analyzed using R software version 2.14.2. The main outcome measure was CPR.

RESULTS

A total of 18 studies were reviewed and assessed for eligibility. One RCT (n=435) and three retrospective studies (n=3,033) met the selection criteria. In a meta-analysis of the selected studies, we found no significant difference in the CPR (odds ratio [OR], 0.96; 95% confidence interval [CI], 0.60-1.55) between the vaginal progesterone and control groups. An analysis of the two retrospective cohort studies that reported the live birth rate (LBR) following FET showed a significantly higher LBR in the vaginal progesterone group (OR, 1.72; 95% CI, 1.21-2.46). A subgroup meta-analysis of FET conducted 5 days after injection of human chorionic gonadotropin showed no significant differences between the two groups with regard to the CPR (OR, 1.18; 95% CI, 0.90-1.55) or miscarriage rate (OR, 0.73; 95% CI, 0.36-1.47).

CONCLUSION

The results of this meta-analysis of the currently available literature suggest that LPS with vaginal progesterone in natural FET cycles does not improve the CPR.

Survey of Fertility Preservation Options Available to Patients With Cancer Around the Globe

Oncofertility focuses on providing fertility and endocrine-sparing options to patients who undergo life-preserving but gonadotoxic cancer treatment. The resources needed to meet patient demand often are fragmented along disciplinary lines. We quantify assets and gaps in oncofertility care on a global scale.

Survey of Third-Party Parenting Options Associated With Fertility Preservation Available to Patients With Cancer Around the Globe

In the accompanying article, “Survey of Fertility Preservation Options Available to Patients With Cancer Around the Globe,” we showed that specific fertility preservation services may not be offered at various sites around the world because of cultural and legal barriers. We assessed global and regional experiences as well as the legal status of third-party reproduction and adoption to serve as a comprehensive international data set and resource for groups that wish to begin oncofertility interventions.

The effects of letrozole on women with endometriosis undergoing ovarian stimulation for in vitro fertilization

This study aimed to analyze the effects of a new protocol with letrozole on the outcomes of in vitro fertilization (IVF) cycles in women with endometriosis. This retrospective cohort study was conducted for women diagnosed with endometriosis undergoing IVF from an infertility clinic. A new protocol, combination therapy with letrozole and gonadotropin, was used from August 2016 to January 2018 ('protocol 1', n = 38). From March 2014 to July 2016, conventional IVF with gonadotropin was administered ('protocol 2', n = 26). Age and ovarian reserve were comparable between the two groups. The patients who received protocol 1 resulted in a significantly lower peak estradiol level in IVF compared with those received protocol 2 (722 ± 1076 pg/mL versus 2168 ± 1521 pg/mL, p < .001). The length of stimulation, the total dose of gonadotropin, number of oocytes retrieved, fertilization rates, and number of embryos obtained were similar between the two groups. The mean percentage of mature oocytes was lower (69.9 ± 23.7% versus 80.2 ± 21.0%, p = .029) in patients with protocol 1. While maintaining low estrogen levels, the combination therapy with letrozole and gonadotropin produce similar oocyte and embryo yield to the conventional IVF protocol in women with endometriosis.

Management of endometriosis-related infertility: Considerations and treatment options

Endometriosis is a common inflammatory disease in women of reproductive age and is one of the major causes of infertility. Endometriosis causes a sustained reduction of ovarian reserve through both physical mechanisms and inflammatory reactions, which result in the production of reactive oxygen species and tissue fibrosis. The severity of endometriosis is related to ovarian reserve. With regard to infertility treatment, medical therapy as a neoadjuvant or adjuvant to surgical therapy has no definite beneficial effect. Surgical treatment of endometriosis can lead to ovarian injury during the resection of endometriotic tissue, which leads to the deterioration of ovarian reserve. To overcome this disadvantage, a multistep technique has been proposed to minimize the reduction of ovarian reserve. When considering surgical treatment of endometriosis in patients experiencing infertility, it should be kept in mind that ovarian reserve can be reduced both due to endometriosis itself and by the process of removing endometriosis. In cases of mild- to moderate-stage endometriosis, intrauterine insemination with ovarian stimulation after surgical treatment may increase the likelihood of pregnancy. In cases of severe endometriosis, the characteristics of the patient should be considered in a multidisciplinary manner to determine the prioritization of treatment modalities, including surgical treatment and assisted reproduction methods such as in vitro fertilization. The risk of cancer, complications after pregnancy, and infection during oocyte retrieval should also be considered when making treatment decisions.

Association of miR-27aA>G, miR-423C>a, miR-449bA>G, and miR-604A>G Polymorphisms with Risk of Recurrent Implantation Failure

Recurrent implantation failure (RIF) is defined when pregnancy failure occurs after two consecutive in vitro fertilization-embryo transfers to the endometrium using at least four high-quality embryos in women. MicroRNAs are well-known function modulators and are involved in many diseases. Recently, studies on microRNA and recurrent pregnancy loss (RPL) have been actively carried out; however, single nucleotide polymorphisms of miRNA in RPL are not well known. Therefore, we set the aim of this study to identify whether polymorphisms in miRNAs that miR-27aA>G, miR-423C>A, miR-449bA>G, and miR-604A>G are risk factors for idiopathic recurrent implantation failure (RIF) in Korean women. Genotyping was assessed with a polymerase chain reaction-restriction fragment length polymorphism assay. We examined polymorphisms in four miRNA genes: miR-27aA>G, miR-423C>A, miR-449bA>G, and miR-604A>G. We found that the miR-27aA>G, miR-449bA>G, and miR-604A>G polymorphisms were significantly associated with a risk of RIF. In addition, the miR-27aA>G and miR-449bA>G polymorphisms were associated with the frequency of implantation failures. Specifically, the miR-449bAG+GG genotype was associated with RIF prevalence (total RIF: adjusted odd ratio [AOR] = 1.584, 95% CI = 1.008-2.490, P = 0.046; IF ≥ 3 group: AOR = 1.747, 95% CI = 1.088-2.803, P = 0.021; IF ≥ 4: AOR = 1.932, 95% CI = 1.122-3.327, P = 0.018). Based on these results, the miR-449b A>G may be a predisposing factor to RIF susceptibility. However, the mechanism underlying the function of miR-449b A>G in RIF remains to be determined and further studies are needed to improve understanding of the roles of miR-449b A>G, using a larger and more heterogeneous cohort.

Oocyte cryopreservation for fertility preservation in women with ovarian endometriosis

RESEARCH-QUESTION

What is the clinical usefulness of oocyte cryopreservation for fertility preservation in women with ovarian endometriosis?

DESIGN

Clinical characteristics were retrospectively analysed in 34 women with endometrioma before a planned ovarian cystectomy. Ovarian stimulation outcomes were compared according to laterality. A one-to-one propensity score-matched analysis was conducted to compare ovarian stimulation outcomes of the first cycle in patients with endometrioma undergoing fertility preservation with those in infertile patients without endometrioma who underwent IVF treatment. The number of oocytes cryopreserved in repeated ovarian stimulation cycles was analysed.

RESULTS

The mean endometrioma size at diagnosis was 6.0 ± 2.5 cm. The mean age, serum anti-Mullerian hormone levels and number of oocytes cryopreserved were 30.7 ± 5.9 years, 1.85 ± 1.14 ng/ml, and 4.8 ± 3.2, respectively. The number of oocytes cryopreserved in bilateral endometrioma compared with unilateral endometrioma patients was 4.1 ± 2.9 versus 5.7 ± 3.4 (P = 0.600). In the propensity score-matched cohort (n = 22 per group), the number of oocytes retrieved was significantly lower in the patients with endometrioma undergoing fertility preservation compared with that in infertile patients without endometrioma (5.4 ± 3.8 versus 8.1 ± 4.8; P = 0.045). A total of 13 (38.2%) patients with endometrioma underwent repeated stimulation. The median (interquartile range) number of cryopreserved oocytes at the first and the second cycle were 3.0 (2.5-6.0) and 5.0 (2.5-7.5), respectively.

CONCLUSIONS

Women with endometrioma should be counselled about oocyte cryopreservation for fertility preservation before surgery. The number of cryopreserved oocytes can be increased by repeated oocyte retrieval.

Effects of cyclic adenosine monophosphate modulators on maturation and quality of vitrified-warmed germinal vesicle stage mouse oocytes

BACKGROUND

It is still one of the unresolved issues if germinal vesicle stage (GV) oocytes can be successfully cryopreserved for fertility preservation and matured in vitro without damage after warming. Several studies have reported that the addition of cyclic adenosine monophosphate (cAMP) modulators to in vitro maturation (IVM) media improved the developmental potency of mature oocytes though vitrification itself provokes cAMP depletion. We evaluated whether the addition of cAMP modulators after GV oocytes retrieval before vitrification enhances maturation and developmental capability after warming of GV oocytes.

METHODS

Retrieved GV oocytes of mice were divided into cumulus-oocyte complexes (COCs) and denuded oocytes (DOs). Then, GV oocytes were cultured with or without dibutyryl-cAMP (dbcAMP, cAMP analog) and 3-isobutyl-l-methylxanthine (phosphodiesterase inhibitor) during the pre-vitrification period for 30 min.

RESULTS

One hour after warming, the ratio of oocytes that stayed in the intact GV stage was significantly higher in groups treated with cAMP modulators. After 18 h of IVM, the percentage of maturation was significantly higher in the COC group treated with dbcAMP. The expression of F-actin, which is involved in meiotic spindle migration and chromosomal translocation, is likewise increased in this group. However, there was no difference in chromosome and spindle organization integrity or developmental competence between the MII oocytes of all groups.

CONCLUSIONS

Increasing the intracellular cAMP level before vitrification of the GV oocytes maintained the cell cycle arrest, and this process may facilitate oocyte maturation after IVM by preventing cryodamage and synchronizing maturation between nuclear and cytoplasmic components. The role of cumulus cells seems to be essential for this mechanism.

Corrigendum: Fertility Preservation for Child and Adolescent Cancer Patients in Asian Countries

[This corrects the article DOI: 10.3389/fendo.2019.00655.].

Predictors of blastocyst formation rate in elective day 5 transfer cycle

This study aimed to investigate the factors affecting blastocyst formation rate. One hundred and seven fresh in vitro fertilisation (IVF) and elective day 5 blastocyst transfer cycles were selected. Univariate and multivariate analyses revealed that intracytoplasmic sperm injection (ICSI) (r = -.236, p = .014 vs. p = .005) was advantageous for blastocyst formation. In addition, the number of mature oocytes (r = -.274, p = .004 vs. p = .002) was a significant factor associated with blastocyst and good-quality blastocyst formation rates (p = .021, r = -.389). Both blastocyst and good-quality blastocyst formation rates were significantly higher with ICSI than with conventional insemination (65.0 ± 24.5% vs. 50.0 ± 21.2%, p = .012; 43.1 ± 22.8% vs. 30.9 ± 19.8%, p = .038, respectively). The number of mature oocytes appears to be the most important predictor of blastocyst formation rate. Additionally, ICSI fertilisation is superior to conventional insemination in terms of blastocyst formation rate.IMPACT STATEMENTWhat is already known on this subject? There are many advantages of blastocyst transfer cycle over cleavage transfer cycle, but there are no known routine selection criteria for the timing of embryo transfer. To date, the number of blastomeres, number of retrieved oocytes, quality of embryos and fertilisation method have been suggested as the important factors involved in blastocyst formation. However, the number of studies on this issue is limited, and some studies have shown conflicting results.What do the results of this study add? This study showed that the number of mature oocytes and ICSI fertilisation are the significant factors associated with blastocyst formation rate in elective day 5 transfer cycle.What are the implications of these findings for clinical practice and/or further research? This paper demonstrated that the number of mature oocytes and the fertilisation method should be considered before embryo transfer. Consideration of these factors would be meaningful in selecting patients who will be suitable for extended culture up to day 5.