Outcomes and cost analysis of single-embryo transfer versus double-embryo transfer.

BACKGROUND: Studies had compared single-embryo transfer to double-embryo transfer with cleavage stage embryos and found that while single-embryo transfer was less costly, it was also associated with a lower live birth rate than double-embryo transfer. A single blastocyst transfer has been shown to improve the live birth rate per cycle compared to single-embryo transfer at cleavage stage. OBJECTIVES: To compare live birth rates and real costs of elective single-embryo transfer to double-embryo transfer and to determine the incremental cost-effectiveness ratio of these two strategies in an unselected pool of women in a single center. DESIGN: Retrospective study. METHODS: We analyzed data of 4232 women who underwent their first fresh in vitro fertilization/intra-cytoplasmic sperm injection cycles with at least two embryos available for transfer in KK Women's and Children's Hospital from 2010 to 2017. RESULTS: Five hundred and sixty-four women underwent elective single-embryo transfer and 3668 women underwent double-embryo transfer. One hundred and fifty-six women who failed to achieve a live birth in their fresh elective single-embryo transfer cycle underwent a sequential thaw single-embryo transfer cycle. Live birth rate of fresh elective single-embryo transfer was significantly higher at 41.3% than that of double-embryo transfer at 32.6%. Cumulative live birth rate for sequential elective single-embryo transfer (fresh elective single-embryo transfer + thaw single-embryo transfer) was 47.9%. After accounting for variables which may affect live birth rates such as age and stage of embryo transfer, the odds of achieving a live birth from double-embryo transfer was 24% lower than that from sequential single-embryo transfer, although not statistically significant. For every live birth gained from an elective single-embryo transfer compared to double-embryo transfer, cost savings were S$20,172 per woman. If a woman had to have a sequential single-embryo transfer after a failed single-embryo transfer in her fresh cycle, cost savings were reduced to S$1476 per woman. CONCLUSION: Single-embryo transfer is a dominant strategy in an unselected population and adopting it in assisted reproductive treatments (ART) can produce cost savings without compromising on live birth rates.

Cohort profile: Singapore Preconception Study of Long-Term Maternal and Child Outcomes (S-PRESTO).

The Singapore Preconception Study of Long-Term Maternal and Child Outcomes (S-PRESTO) is a preconception, longitudinal cohort study that aims to study the effects of nutrition, lifestyle, and maternal mood prior to and during pregnancy on the epigenome of the offspring and clinically important outcomes including duration of gestation, fetal growth, metabolic and neural phenotypes in the offspring. Between February 2015 and October 2017, the S-PRESTO study recruited 1039 Chinese, Malay or Indian (or any combinations thereof) women aged 18-45 years and who intended to get pregnant and deliver in Singapore, resulting in 1032 unique participants and 373 children born in the cohort. The participants were followed up for 3 visits during the preconception phase and censored at 12 months of follow up if pregnancy was not achieved (N = 557 censored). Women who successfully conceived (N = 475) were characterised at gestational weeks 6-8, 11-13, 18-21, 24-26, 27-28 and 34-36. Follow up of their index offspring (N = 373 singletons) is on-going at birth, 1, 3 and 6 weeks, 3, 6, 12, 18, 24 and 36 months and beyond. Women are also being followed up post-delivery. Data is collected via interviewer-administered questionnaires, metabolic imaging (magnetic resonance imaging), standardized anthropometric measurements and collection of diverse specimens, i.e. blood, urine, buccal smear, stool, skin tapes, epithelial swabs at numerous timepoints. S-PRESTO has extensive repeated data collected which include genetic and epigenetic sampling from preconception which is unique in mother-offspring epidemiological cohorts. This enables prospective assessment of a wide array of potential determinants of future health outcomes in women from preconception to post-delivery and in their offspring across the earliest development from embryonic stages into early childhood. In addition, the S-PRESTO study draws from the three major Asian ethnic groups that represent 50% of the global population, increasing the relevance of its findings to global efforts to address non-communicable diseases.

Ovarian biomarkers predict controlled ovarian stimulation for in vitro fertilisation treatment in Singapore.

INTRODUCTION: Ovarian biomarkers have been shown to predict responses to controlled ovarian hyperstimulation (COH) during in vitro fertilisation (IVF) in predominantly Caucasian populations, with limited studies performed in Southeast Asian women in Singapore. METHODS: We evaluated the performance of serum anti-Müllerian hormone (AMH), follicle-stimulating hormone and oestradiol levels, antral follicle count (AFC), body mass index, ovarian volume, and age to establish thresholds for the prediction of poor (< 4 oocytes retrieved) and excessive responses (> 19 oocytes retrieved) in 263 women undergoing COH. Univariate and multivariate logistic regression analysis and receiver operating characteristic curves were used to calculate probabilities for poor and excessive responders to COH. RESULTS: 36 (13.7%) and 50 (19.0%) women had poor and excessive response to COH, respectively. An AMH value of 0.69 ng/mL predicted poor ovarian response with positive likelihood ratio (LR) of 2.94, compared to an AFC of ≤ 5 when the positive LR is 2.36. Conversely, an AMH value of ≥ 3.06 ng/mL predicted excessive ovarian response with positive LR of 2.24, compared to an AFC cut-off of ≥ 12 with positive LR of 1.93. CONCLUSION: AMH levels and AFC are equivalent in the prediction of both poor and excessive ovarian response in women undergoing IVF. Our study highlights the importance of establishing population-specific cut-off biomarker values so that protocols can be tailored to optimise IVF treatment.

Author Correction: Anthropometric measures and HbA1c to detect dysglycemia in young Asian women planning conception: The S-PRESTO cohort.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Anthropometric measures and HbA1c to detect dysglycemia in young Asian women planning conception: The S-PRESTO cohort.

We investigated whether adding anthropometric measures to HbA1c would have stronger discriminative ability over HbA1c alone in detecting dysglycemia (diabetes and prediabetes) among Asian women trying to conceive. Among 971 Singaporean women, multiple regression models and area under receiver-operating characteristic (AUROC) curves were used to analyze associations of anthropometric (weight, height, waist/hip circumferences, 4-site skinfold thicknesses) and HbA1c z-scores with dysglycemia (fasting glucose ≥6.1 mmol/L with 2-hour glucose ≥7.8 mmol/l). The prevalence of dysglycemia was 10.9%. After adjusting for sociodemographic/medical history, BMI (Odds Ratio [OR] = 1.62 [95%CI 1.32-1.99]), waist-to-height ratio (OR = 1.74 [1.39-2.17]) and total skinfolds (OR = 2.02 [1.60-2.55]) showed the strongest associations with dysglycemia but none outperformed HbA1c (OR = 4.09 [2.81-5.94]). After adjustment for history, adding BMI, waist-to-height ratio and total skinfolds (anthropometry trio) as continuous variables to HbA1c (AUROC = 0.80 [95%CI 0.75-0.85]) performed similarly to HbA1c alone (AUROC = 0.79 [0.74-0.84]). However, using clinically-defined thresholds without considering history, as in common clinical practice, BMI ≥ 23 kg/m2 + HbA1c ≥ 5.7% (AUROC = 0.70 [0.64-0.75]) and anthropometry trio + HbA1c ≥ 5.7% (AUROC = 0.71 [0.65-0.76]) both outperformed HbA1c ≥ 5.7% alone (AUROC = 0.61 [0.57-0.65]). In a two-stage strategy, incorporating BMI ≥ 23 kg/m2 alongside HbA1c ≥ 5.7% into first-stage screening to identify high risk women for subsequent oral glucose tolerance testing improves dysglycemia detection in Asian women preconception.

Peritoneal Fluid Cytokines Reveal New Insights of Endometriosis Subphenotypes.

Endometriosis is a common inflammatory gynecological disorder which causes pelvic scarring, pain, and infertility, characterized by the implantation of endometrial-like lesions outside the uterus. The peritoneum, ovaries, and deep soft tissues are the commonly involved sites, and endometriotic lesions can be classified into three subphenotypes: superficial peritoneal endometriosis (PE), ovarian endometrioma (OE), and deep infiltrating endometriosis (DIE). In 132 women diagnosed laparoscopically with and without endometriosis (n = 73, 59 respectively), and stratified into PE, OE, and DIE, peritoneal fluids (PF) were characterized for 48 cytokines by using multiplex immunoassays. Partial-least-squares-regression analysis revealed distinct subphenotype cytokine signatures-a six-cytokine signature distinguishing PE from OE, a seven-cytokine signature distinguishing OE from DIE, and a six-cytokine-signature distinguishing PE from DIE-each associated with different patterns of biological processes, signaling events, and immunology. These signatures describe endometriosis better than disease stages (p < 0.0001). Pathway analysis revealed the association of ERK1 and 2, AKT, MAPK, and STAT4 linked to angiogenesis, cell proliferation, migration, and inflammation in the subphenotypes. These data shed new insights on the pathophysiology of endometriosis subphenotypes, with the potential to exploit the cytokine signatures to stratify endometriosis patients for targeted therapies and biomarker discovery.

Laparoscopic Tubal Re-anastomosis or In Vitro Fertilisation in Previously Ligated Patients: A Comparison of Fertility Outcomes and Survey of Patient Attitudes

INTRODUCTION: We aim to compare live birth rates, cost analysis and a survey of patient attitudes between laparosopic tubal re-anastomosis and in vitro fertilisation (IVF). MATERIALS AND METHODS: A retrospective study was done in a single reproductive medicine and IVF unit in Singapore from January 2011 to December 2016. Previously ligated patients underwent either laparoscopic tubal re-anastomosis or IVF. The primary outcome was first live birth after treatment. Interval to first pregnancy, miscarriage and ectopic pregnancies were also reported. Patients attending the subfertility clinic completed a questionnaire on IVF and tubal re-anastomosis on preferred choice of treatment, before and after reading an information sheet. RESULTS: Twelve patients underwent tubal re-anastomosis while 31 patients underwent IVF treatment. Pregnancy (75.0% vs 35.5%) and live birth (58.3% vs 25.8%) were significantly higher in the tubal surgery group (P <0.05%) after transferring all available embryos in one stimulated IVF cycle. Cost per live birth was lower in the tubal surgery group (SGD27,109 vs SGD52,438). One hundred patients participated in the survey. A majority of patients preferred tubal surgery to IVF (68.2% vs 31.8%) before given information on the procedures, but indicated a preference for IVF (54.6%) to surgery (45.4%) after receiving information on the procedures. CONCLUSIONS: For women less than 40 years of age, desiring fertility after tubal ligation, laparoscopic tubal re-anastomosis offers better live birth rates and cost-effectiveness. Patients in Singapore are equivocal as to their preference after education regarding the choices. Thus, laparoscopic tubal re-anastomosis remains a viable alternative to IVF treatment.

One Hospital Department with Three Affiliated Medical Schools - Yea or Nay? A Cross-sectional Survey of Students and Tutors.

This article was migrated. The article was marked as recommended. Background The experience of teaching students from multiple medical schools with separate curriculums and learning ethos within a single healthcare institution is not well-documented in literature. Objective We aimed to identify the benefits and challenges of having students from three medical schools train within one department from the clinical tutors' and medical students' viewpoint. Methods This was a cross-sectional study at KK Women's and Children's Hospital (KKH). A survey was conducted on clinical tutors and students from three medical schools for their viewpoints on a 5-point Likert scale. Results 91 of 100 (91%) students and 51 of 60 (85%) tutors returned the survey. 95.6% of students and 94.1% of tutors agreed that it was important for KKH to be involved in the teaching of all three medical schools. 83.5% of students and 76.5% of tutors believed they would benefit from shared teaching and learning materials. 84.3% of tutors and 83.6% of students agreed that they could be exposed to new teaching methods while 84.7% of students and 72.5% of tutors believed that opportunities to collaborate between schools would arise. However, 25 (49%) tutors and 58 (63.7%) students believed that there may be limited supervision. Students (60.4%) and tutors (56.9%) alike felt that there would be a lack of learning space. Conclusion Both students and tutors believed that it was important for medical students for the department in KKH to be involved in the teaching of all three medical schools. Benefits perceived included shared teaching and learning resources, exposure to new teaching methods and opportunity for collaboration across medical schools. Through careful planning of rotations and supportive leadership, hospitals can optimise teaching capabilities allowing students and tutors to benefit from advantages of teaching of students from multiple medical schools.

Comparison between Single and Double Cleavage-Stage Embryo Transfers, Single and Double Blastocyst Transfers in a South East Asian In Vitro Fertilisation Centre.

INTRODUCTION: This study investigated the differences in clinical pregnancy rate (CPR), live birth rate (LBR) and multiple pregnancy rate (MPR) between double cleavage-stage embryo transfers compared to single and double blastocysts stage embryo transfers in a single academic medical centre. MATERIALS AND METHODS: This was a retrospective cohort study performed at the KK Women's and Children's Hospital In Vitro Fertilisation (KKIVF) Centre of all women who underwent fresh-cycle in vitro fertilisation/intracytoplasmic sperm injection (IVF/ICSI) cycles over a 5-year period. The outcome measures were CPR, LBR and MPR. The study included 5294 cycles, of which 539 patients underwent single embryo transfer (SET); 4533 patients underwent double embryo transfer (DET); 84 patients underwent double blastocyst embryo transfer (DBT); and 65 patients underwent single blastocyst embryo transfer (SBT). RESULTS: The mean age of patients undergoing single blastocysts stage embryo transfer was lower than the other 2 groups. The DET, single and double blastocysts stage embryo transfer groups achieved similar LBR (33.9%, 38.7%, 35.4%, P >0.05) and CPR (42.4%, 46.2%, 46.9%). CONCLUSION: We found that single blastocysts stage embryo transfer is associated with similar LBR and CPR compared to double blastocysts stage embryo transfer and DET, with lower MPRs, and should be offered as standard practice, where possible.

Elevated peritoneal fluid ceramides in human endometriosis-associated infertility and their effects on mouse oocyte maturation.

OBJECTIVE: To characterize the peritoneal fluid (PF) sphingolipid profile in endometriosis-associated infertility (EAI), and to assess the plausible functional role(s) of ceramides in oocyte maturation potential. DESIGN: Retrospective case-control study and in vitro mouse oocyte study. SETTING: University-affiliated hospital and university laboratory. SUBJECTS: Twenty-seven infertile patients diagnosed with endometriosis and 20 infertile patients who did not have endometriosis; BALB/c female mice. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): PF sphingolipid concentrations. Number of metaphase II (MII) mouse oocytes. RESULT(S): Liquid chromatography-tandem mass spectrometry revealed 11 significantly elevated PF sphingolipids in infertile women with severe endometriosis compared with infertile women without endometriosis (change >50%, false discovery rate ≤10%). Logistic regression analysis identified three very-long-chain ceramides potentially associated with EAI. Functional studies revealed that very-long-chain ceramides may compromise or induce murine MII oocyte maturation. The oocyte maturation effects induced by the very long-chain ceramides were triggered by alterations in mitochondrial superoxide production in a concentration-dependent manner. Scavenging of mitochondrial superoxide reversed the maturation effects of C24:0 ceramide. CONCLUSION(S): EAI is associated with accumulation of PF very-long-chain ceramides. Mouse studies demonstrated how ceramides affect MII oocyte maturation, mediating through mitochondrial superoxide. These results provide an opportunity for direct functional readout of pathophysiology in EAI, and future therapies targeted at this sphingolipid metabolism may be harnessed for improved oocyte maturation.

Age-related nomograms for antral follicle count and anti-Mullerian hormone for subfertile Chinese women in Singapore.

BACKGROUND: Antral follicle count (AFC) and anti-Mullerian hormone (AMH) are known as the most reliable markers of a woman's ovarian reserve and are related to age. There is currently no specific local age-related centile charts for AFC and AMH. Therefore, we aim to examine the relationship between AFC and AMH with age and construct age-related nomograms among a subfertile Asian population. METHODS: This is a study involving Chinese women who had their AFC and AMH measured as part of their subfertility screening from December 2010 until November 2014 in KK Women's and Children's Hospital, Singapore. Ordinary least squares regression analysis was used to estimate the relationship of AFC and AMH with age, while age-related AFC and AMH nomograms for the 3rd, 10th, 25th, 50th, 75th, 90th and 97th percentiles were produced using the lambda-mu-sigma method. RESULTS: A total of 1,009 women, aged 26 to 44 year-old, were included. On average, the AFC and AMH decreased respectively by 0.79 follicle (95% confidence interval -0.93, -0.64) and 0.38 ng/mL (95% confidence interval -0.43, -0.32) per year of age. The age-related nomograms of AFC showed an approximately linear pattern, inversely correlated with age, regardless of the percentile. For AMH, the pattern is linear for the 75th percentile and below but shows a slightly accelerating decline for the 90th and 97th percentile. Overall, there were large inter-individual variations in AFC and AMH up to about 40 year-old. CONCLUSION: The declines of AFC and AMH over age are mostly linear among subfertile Chinese women in Singapore. The age-related AFC and AMH nomograms could be used as a reference chart by fertility practitioners. However, future validation with longitudinal data is required.

Limited value of pro-inflammatory oxylipins and cytokines as circulating biomarkers in endometriosis - a targeted 'omics study.

Endometriosis is a common, complex gynecologic disorder characterized by the presence of endometrial-like tissues at extrauterine sites. Elevation in protein and lipid mediators of inflammation including oxylipins and cytokines within the peritoneum characterize the inflamed pelvic region and may contribute to the survival and growth of displaced endometrial tissues. The presence of a clinically silent but molecularly detectable systemic inflammation in endometriosis has been proposed. Thus, we examined serum oxylipin and immunomodulatory protein levels in 103 women undergoing laparoscopy to evaluate systematically any involvement in systemic pathophysiological inflammation in endometriosis. Oxylipin levels were similar between women with and without endometriosis. Stratification by menstrual phase or severity did not offer any difference. Women with ovarian endometriosis had significantly lower 12-HETE relative to peritoneal endometriosis (-50.7%). Serum oxylipin levels were not associated with pre-operative pain symptoms. Changes to immunomodulatory proteins were minimal, with IL-12(p70), IL-13 and VEGF significantly lower in mild endometriotic women compared to non-endometriotic women (-39%, -54% and -76% respectively). Verification using C-reactive protein as a non-specific marker of inflammation further showed similar levels between groups. The implications of our work suggest pro-inflammatory mediators in the classes studied may have potentially limited value as circulating biomarkers for endometriosis, suggesting of potentially tenuous systemic inflammation in endometriosis.

Estimating cumulative live-birth rates after IVF treatment with Kaplan-Meier and competing risk methods.

OBJECTIVE(S): To explore the use of competing risk (CR) as compared to the commonly used Kaplan-Meier (KM) methodology in estimating the cumulative live-birth rate (CLBR) after IVF Treatment in a context of high dropout rates and informative censoring. STUDY DESIGN: We compare the KM and CR methodologies for estimating 2-year CLBR in a retrospective cohort of 2779 patients undergoing 5002 embryo transfers over a period of 9 years, from 2000 to 2008, at KKIVF Centre. RESULTS: We observed a total of 1105 LB (39.8%), and a dropout rate of 44.2% (1228 patients). The overall CLBR is lower with CR compared with KM method (39% vs 52%) after up to nine embryo-transfer cycles over a period of two years. The highest CLBR was achieved for ovulation disorders (57% vs 49%, KM vs CR) followed by male factors (54% vs 43%, KM vs CR), with poorer outcomes from patients with decreased ovarian reserve (37% vs 16%, KM vs CR) and endometriosis (36% vs 25%, KM vs CR). As dropouts in our cohort are generally older and more likely to have poorer ovarian reserves, the CR method, which accounted for these dropouts, is likely to give more meaningful estimation of IVF success rates. CONCLUSION(S): The CR method should be considered as a useful alternative in deriving CLBR for IVF treatment where dropout rates are high and when informative censoring is involved.

GnRH antagonist pre-treatment: one centre's experience for IVF-ICSI cycle scheduling.

Scheduling gonadotrophin-releasing hormone antagonist (GnRH-ant) cycles for IVF intracytoplasmic sperm injection in patients is a challenge because of unpredictable ovum retrieval procedures on weekends, when less manpower is available. Recently, the use of GnRH-ant pre-treatment to delay an IVF and intracytoplasmic sperm injection (ICSI) cycle showed no negative effect on clinical pregnancy rates. An age-matched, case-control study was conducted to evaluate the effectiveness of such pre-treatment for scheduling purposes. Patients (n = 140) undergoing their first ovarian stimulation for IVF-ICSI were included. Patients starting their stimulation on Tuesdays or Wednesdays were most likely to have their ovum retrieval procedure on Saturdays. Seventy patients received a 3-day course of GnRH-ant before starting stimulation, and were compared with 70 age-matched controls not receiving pre-treatment. The main outcomes were the proportion of ovum retrieval procedures occurring on Saturdays, clinical pregnancy rate and live birth rates. A five-fold reduction in the number of ovum retrievals occurred on Saturdays compared with controls (7.1% versus 34.3%; OR 0.15; 95% CI 0.05 to 0.42; P < 0.001), with no significant differences in clinical pregnancy rate (40.9% versus 37.5%) and live birth rate (27.3% versus 31.3%). GnRH-ant pre-treatment is an effective tool for scheduling of GnRH-ant cycles.

GnRH agonist trigger and ovarian hyperstimulation syndrome: relook at 'freeze-all strategy'.

A case is reported of early onset ovarian hyperstimulation syndrome (OHSS) after gonadotrophin-releasing hormone agonist (GnRHa) trigger for final oocyte maturation in a GnRH antagonist protocol. The use of GnRHa in place of HCG as a trigger for final oocyte maturation in an antagonist IVF cycle has been proposed as a method for preventing OHSS in predicted high-responders. This approach, however, did not prevent the occurrence of OHSS in our case despite a freeze-all strategy. To the best of our knowledge, this is a possible index case of severe OHSS with GnRHa trigger for oocyte maturation without any luteal HCG rescue for a high responder, despite IVF cycle segmentation.

CD26/DPPIV down-regulation in endometrial stromal cell migration in endometriosis.

OBJECTIVE: To test the hypothesis that endometrial stromal cells (ESCs) in endometriosis exhibit increased cell motility under hypoxia. DESIGN: Prospective case-control study. SETTING: University research laboratory. PATIENT(S): Women with endometriosis (n = 18) or benign gynecological disease (n=19). INTERVENTION(S): Eutopic ESCs were cultured under normoxia (20% O2) or hypoxia (6.5% O2), and migration and invasion capacity assayed, with pathway-focused polymerase chain reaction (PCR) array and ELISAs performed. CD26/dipeptidyl peptidase IV (DPPIV) expression was determined by flow cytometric analysis and enzymatic activity assay. The ESCs supplemented with Diprotin A (CD26 inhibitor), stromal cell-derived factor-1α, or AMD3100 (C-X-C motif receptor 4; CXCR4 blocker) were assayed for their migratory potential. MAIN OUTCOME MEASURE(S): Endometrial stromal cell migration and invasion under hypoxia. RESULT(S): Endometriotic ESCs showed significantly higher migration and invasion through collagen gels under hypoxia compared with nonendometriotic ESCs. The PCR array revealed down-regulation of the migration inhibitor CD26/DPPIV and up-regulation of angiogenic factors (vascular endothelial growth factor A, C-X-C motif Ligand 6; CXCL6) in endometriotic ESCs under hypoxia. The CD26/DPPIV surface expression and activity as well as angiogenic protein secretions suggested that the molecular mechanisms underlying aberrant migratory and angiogenic behavior in endometriotic ESCs. A combinatorial treatment with diprotin A and stromal cell-derived factor-1α effectively enhanced migration and invasion preferentially in endometriotic ESCs cultured hypoxically. CONCLUSION(S): Loss of CD26/DPPIV under hypoxia and the subsequent increase in migratory and angiogenic factors may favor conditions for lesion development in endometriosis.

Human embryo cryopreservation: one-step slow freezing does it all?

PURPOSE: Previous studies have shown that a modified one-step slow freezing method with higher sucrose concentration (0.2 M) can achieve higher embryo and blastomere survival rates that are comparable to vitrification. However, no study has evaluated the efficacy of a one-step method using commercial slow freezing kit without altering its composition. This retrospective study examines the effects of using 1.5 M PROH with 0.1 M sucrose (F2 medium) alone in a one-step slow freezing method compared to the conventional two-step method. METHODS: Cleavage stage embryos from 526 thaw cycles previously cryopreserved by either the conventional two-step slow freezing method or the modified one-step method were studied. The embryo and blastomere survival rates, cleavage rate, clinical pregnancy rate and live birth rate were compared between the two groups. RESULTS: The results showed that the embryo survival rate was significantly higher in the modified one-step method compared to the conventional two-step method (86.9 % and 83.1 %, respectively; p = 0.04). Total blastomere survival rate was also significantly increased as a result of the modification (81.0 % versus 76.5 %; p < 0.001). However, there was no statistical difference in the cleavage rates, clinical pregnancy rates (CPR/ET) and live birth rates between the two methods. CONCLUSIONS: Slow freezing using the one-step method is superior to the conventional two-step method in terms of embryo and blastomere survival rates without affecting cleavage rate and clinical outcomes. It can be routinely applied to cleavage stage embryo cryopreservation in IVF centres for greater workflow efficiency.