Individual participant data meta-analysis of trials comparing frozen versus fresh embryo transfer strategy (INFORM): a protocol.

INTRODUCTION: Existing randomised controlled trials (RCTs) comparing a freeze-all embryo transfer strategy and a fresh embryo transfer strategy have shown conflicting results. A freeze-all or a fresh transfer policy may be preferable for some couples undergoing in-vitro fertilisation (IVF), but it is unclear which couples would benefit most from each policy, how and under which protocols. Therefore, we plan a systematic review and individual participant data meta-analysis of RCTs comparing a freeze-all and a fresh transfer policy. METHODS AND ANALYSIS: We will search electronic databases (Medline, Embase, PsycINFO and CENTRAL) and trial registries (ClinicalTrials.gov and the International Clinical Trials Registry Platform) from their inception to present to identify eligible RCTs. We will also check reference lists of relevant papers. The search was performed on 23 September 2020 and will be updated. We will include RCTs comparing a freeze-all embryo transfer strategy and a fresh embryo transfer strategy in couples undergoing IVF. The primary outcome will be live birth resulting from the first embryo transfer. All outcomes listed in the core outcome set for infertility research will be reported. We will invite the lead investigators of eligible trials to join the Individual participant data meta-analysis of trials comparing frozen versus fresh embryo transfer strategy (INFORM) collaboration and share the deidentified individual participant data (IPD) of their trials. We will harmonise the IPD and perform a two-stage meta-analysis and examine treatment-covariate interactions for important baseline characteristics. ETHICS AND DISSEMINATION: The study ethics have been granted by the Monash University Human Research Ethics Committee (Project ID: 30391). The findings will be disseminated via presentations at international conferences and publication in peer-reviewed journals. PROSPERO REGISTRATION NUMBER: CRD42021296566.

The effect of ovarian follicle size on oocyte and embryology outcomes.

OBJECTIVE: To identify relationships between the size of punctured ovarian follicles and subsequent embryology outcomes. DESIGN: Prospective observational cohort study. SETTING: Private fertility center. PATIENTS: One hundred fifty-seven oocyte retrievals performed during the study period. INTERVENTIONS: The diameter of punctured follicles was ultrasonically measured during routine oocyte collection. The resulting embryos were group-cultured to the blastocyst stage and classified into 8 groups according to follicle size (≤9.5, 10-12.5, 13-15.5, 16-18.5, 19-21.5, 22-24.5, 25-27.5, and ≥28 mm). MAIN OUTCOME MEASURE: Rate of good-quality blastocysts per follicle puncture. RESULTS: This study included 4,539 follicle punctures, 2,348 oocytes, 1,772 mature oocytes, 1,258 bipronuclear (2pn) oocytes, and 571 good-quality blastocysts derived from 157 oocyte retrievals. The per-puncture yields of oocytes, mature oocytes, 2pn oocytes, and good-quality blastocysts were associated with the size of the punctured follicle. The rates of good-quality blastocysts per punctured follicle were 2.2% (≤9.5 mm), 6.2% (10-12.5 mm), 11.9% (13-15.5 mm), 14.5% (16-18.5 mm), 18.9% (19-21.5 mm), 17.5% (22-24.5 mm), 15.9% (25-27.5 mm), and 16.0% (≥28 mm). When compared with the overall average, punctures of follicles in groups ≤12.5 mm in diameter had significantly inferior yields of good-quality blastocysts, whereas punctures of follicles in groups 19-24.5 mm in diameter were associated with significantly greater than average yields of good-quality blastocysts. Other groups did not differ significantly from average. No correlation was observed between follicle diameter and ploidy of biopsied blastocysts. CONCLUSIONS: Punctures of follicles ≤12.5 mm in diameter rarely result in good-quality blastocysts. The yield of good-quality blastocysts progressively increases with follicle size up to approximately 19 mm in diameter, with no substantial decline above that size. The ploidy of the blastocysts that form appears to be unaffected by follicle size.

The change in endometrial thickness following progesterone exposure correlates with in vitro fertilization outcome after transfer of vitrified-warmed blastocysts.

PURPOSE: To determine if the change in endometrial thickness following exogenous progesterone (P) initiation correlates with outcome following autologous transfer of a single thawed blastocyst. METHODS: The study is a retrospective observational cohort study conducted at a private fertility center. Patients scheduled for thawed blastocyst transfer received artificial endometrial preparation (artificial cycle FET) and underwent serial ultrasonography. The main outcomes were the rate of ongoing pregnancy (fetal heart motion at 12 weeks of gestation) and early pregnancy loss. Logistic regression was used to test for correlations between these outcomes and the change in endometrial thickness while adjusting for potential confounders (patient age, embryo quality, and the use of genetic testing). RESULTS: There were 232 qualifying autologous single-blastocyst transfers in the 20-month study period ending 31 December 2019. Mean endometrial thicknesses were 3.8 mm, 10.0 mm, and 11.2 mm at baseline, P initiation, and at transfer, respectively. The change in endometrial thickness after exogenous P exposure ranged from - 5 to + 9 mm and negatively correlated with ongoing pregnancy in logistic regression analyses. Specifically, ongoing pregnancy rates per transfer were 63.2% in 19 cases where endometria compacted by 10% or more, 64.2% in 95 cases where there was unchanged endometrial thickness, and 52.5% in 118 cases where endometria expanded. CONCLUSIONS: The change in endometrial thickness after P initiation was associated with the probability of ongoing pregnancy but not with early pregnancy loss. Ongoing pregnancy rates were greater in endometria with negative growth (compaction) when compared to endometria that grew (expanded) after P exposure.

Comparison of birth weights in patients randomly assigned to fresh or frozen-thawed embryo transfer.

OBJECTIVE: To estimate birth weight differences between patients randomized to fresh or thawed ET. DESIGN: Post hoc analysis of results from two similar randomized trials. SETTING: Private fertility center. PATIENT(S): One hundred thirty-four first-time IVF patients, ages 18-40 years at oocyte retrieval, who had live birth. INTERVENTION(S): Patients were randomly assigned to have either fresh blastocyst transfer or all bipronuclear oocytes frozen followed by thaw, extended culture, and blastocyst transfer in a subsequent cycle. Preimplantation genetic screening was not allowed. MAIN OUTCOME MEASURE(S): Mean birth weight. RESULT(S): After allowing for the contributions of multiple significant variables (gestational age at birth, the presence of a vanished twin, number of infants delivered) in multiple linear regression, the adjusted mean birth weight was 166 g (95% confidence interval, 43-290 g) lower after fresh blastocyst transfer when compared with transfer of blastocysts derived from thawed bipronuclear oocytes. CONCLUSION(S): Birth weights are lower in cycles with fresh blastocyst transfer after controlled ovarian stimulation than in transfers of frozen-thawed embryos in the absence of ovarian stimulation. This finding confirms similar results reported in many retrospective studies. CLINICAL TRIAL REGISTRATION NUMBERS: NCT00963625 and NCT00963079.

The risk of embryo-endometrium asynchrony increases with maternal age after ovarian stimulation and IVF.

This retrospective cohort analysis examined the effects of maternal age on the incidence of factors associated with embryo-endometrium asynchrony in fresh autologous blastocyst transfer. The study included 1169 routine fresh autologous blastocyst transfers. The main outcome measure was asynchronous transfer defined by delayed (day 6) blastocyst transfer or elevated pre-ovulatory serum progesterone level. Compared with patients younger than 35 years, patients 35 years or older had increased risk of having at least one risk factor for asynchronous transfer, including premature progesterone elevation or delayed blastocyst transfer (RR 1.36; 95% CI 1.24 to 1.50). The older group had increased risk of simultaneously having both risk factors (RR 1.61, 95% CI 1.17 to 2.21) compared with the younger group. In patients younger than 35 years, live birth rate per transfer was 62.9% with day 5 transfer and low progesterone, declining to 27.9% for day 6 transfer combined with elevated progesterone. In patients 35 years or older, live birth rate per transfer was 38.0% with day 5 transfer and low progesterone, declining to 18.1% for day 6 transfer combined with elevated progesterone. Indicators of embryo-endometrium asynchrony increase in prevalence as women age and asynchrony disproportionately decreases birth rates in older patients.

Freeze-all at the blastocyst or bipronuclear stage: a randomized clinical trial.

OBJECTIVE: To compare outcomes for patients randomized to have all embryos cryopreserved at the blastocyst stage or at the bipronuclear stage with subsequent post-thaw culture to the blastocyst stage. DESIGN: Randomized controlled trial. SETTING: Private fertility center. PATIENT(S): This study included 140 women, age 18-40 years, with at least eight antral follicles, and day 3 FSH <10 IU/L undergoing IVF. INTERVENTION(S): After oocyte retrieval, subjects were randomized to have entire embryo cohorts cryopreserved at either the bipronuclear stage (2PN Cryo group) or at the blastocyst stage (Blast Cryo group). MAIN OUTCOME MEASURE(S): Ongoing pregnancy (viable fetal heart motion at 10 weeks' gestation) per oocyte retrieval through the first transfer attempt. RESULT(S): No significant differences were observed between the two study groups in age at retrieval, body mass index, antral follicle count, day 3 FSH level, or IVF cycle parameters. No significant differences were observed in ongoing pregnancy rate per retrieval (62.0%; 95% confidence interval [CI], 50.3%-72.4%) in the 2PN Cryo group; and 55.1%; 95% CI, 42.6%-67.1% in the Blast Cryo group), implantation rate (60.0% vs. 62.7%), ongoing pregnancy rate per thaw (62.0% vs. 59.4%), ongoing pregnancy rate per transfer (67.7% vs. 69.1%), and the cumulative ongoing pregnancy rate per retrieval from all thaws to date of embryos derived from the study retrieval cycle (64.8% vs. 60.9%). CONCLUSION(S): Freeze-all at the blastocyst stage or at the bipronuclear stage has similar efficacy and IVF outcomes. The choice between them may depend primarily on logistical factors. CLINICAL TRIAL REGISTRATION NUMBER: NCT01247987.

Freeze-all can be a superior therapy to another fresh cycle in patients with prior fresh blastocyst implantation failure.

Implantation failure has various causes, including impaired uterine receptivity following ovarian stimulation. This retrospective cohort study compared outcomes in patients with prior implantation failure who elected to undergo another fresh cycle versus those who opted for embryo cohort cryopreservation (freeze-all) and subsequent thaw. There were 269 patients with implantation failure following fresh autologous blastocyst transfer opting to undergo a subsequent cycle, with 163 choosing another fresh cycle and 106 electing freeze-all and subsequent thaw. Multiple logistic regression analysis indicated that cohort cryopreservation was associated with greater chance of live birth when compared with another fresh cycle (P < 0.0001). The odds ratio for live birth with freeze-all relative to a fresh cycle was 3.8 (95% CI 2.1-7.2). A second analysis was then performed using cumulative live birth rate as the outcome measure. Multiple logistic regression indicated freeze-all was associated with greater cumulative live birth rate than was a fresh cycle (OR 1.9, 95% CI 1.1-3.3, P = 0.0287). These findings suggest that, following implantation failure with fresh blastocysts, patients have a significantly greater chance of live birth with freeze-all and subsequent thaw than with another fresh cycle.

Clinical rationale for cryopreservation of entire embryo cohorts in lieu of fresh transfer.

Recent dramatic increases in success rates with frozen-thawed embryo transfer (FET) are encouraging, as are numerous findings of several reduced risks with FET when compared with fresh transfer. These reduced risks include low birth weight and prematurity, among others. However, FET is also associated with increased risks of macrosomia and large for gestational age. There have been reports of greater implantation and pregnancy rates with FET than with fresh autologous embryo transfer, suggesting superior endometrial receptivity in the absence of ovarian stimulation. As cryo-technology evolves, there is potential for further increase in FET success rates, but for now it may be best to follow an individualized approach, balancing fresh transfer and embryo cohort cryopreservation options while considering patient characteristics, cycle parameters, and clinic success rates.

Matched-cohort comparison of single-embryo transfers in fresh and frozen-thawed embryo transfer cycles.

OBJECTIVE: To discern the potential effect of ovarian stimulation on implantation potential by comparing ongoing pregnancy rates from matched blastocysts in fresh and frozen-thawed single-embryo-transfer cycles. DESIGN: Matched cohort study. SETTING: Private fertility center. PATIENT(S): Ninety-three matched pairs of single-blastocyst transfer. INTERVENTION(S): Fresh and frozen-thawed embryo transfers were matched on embryo parameters and patient age. MAIN OUTCOME MEASURE(S): Ongoing pregnancy at 10 weeks' gestation. RESULT(S): The fresh and frozen-thawed groups did not differ significantly in blastocyst diameter, inner cell mass size, trophectoderm cell count, patient age, use of genetic screening, or presence of supernumerary embryos. The ongoing pregnancy rate was significantly greater in the frozen-thawed group than in the fresh group for transfers of day 6 blastocysts (54.3% vs. 17.1%, respectively), but not for day 5 blastocysts (60.9% vs. 56.5%, respectively). This resulted in the overall ongoing pregnancy rate to be significantly greater in the frozen-thawed group than in the fresh group (55.9% vs. 26.9%, respectively). CONCLUSION(S): Autologous day 6 blastocysts transferred in frozen-thawed cycles have significantly greater chance of viable implantation than morphologically equivalent embryos transferred in fresh cycles. This advantage appears to result from impaired implantation of day 6 blastocysts in fresh transfers after ovarian stimulation, suggesting that embryo-endometrium asynchrony is a major cause of impaired endometrial receptivity after ovarian stimulation.

Frozen-thawed embryo transfer is associated with a significantly reduced incidence of ectopic pregnancy.

OBJECTIVE: To compare the incidence of ectopic pregnancy (EP) after fresh ET and thawed ET. DESIGN: Retrospective cohort study. SETTING: Private fertility center. PATIENT(S): This retrospective study included 2,150 blastocyst transfers, including all 1,460 fresh autologous blastocyst transfers and all 690 transfers of autologous blastocysts derived from post-thaw extended culture of thawed bipronuclear oocytes in the 8-year study period 2004-2011. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Visualized EP and treated persistent pregnancy of unknown location. RESULT(S): The rate of visualized EP was 1.5% in pregnancies in fresh autologous cycles, which was significantly more than the rate of 0 with autologous post-thaw extended culture. The rates of treated persistent pregnancy of unknown location were 2.5% and 0.3% in these two groups, respectively, a difference that was also statistically significant (relative risk 7.3, 95% confidence interval 1.7-31.0). CONCLUSION(S): Relative to fresh transfer, thawed ET was associated with significantly reduced incidence of EP. These findings are consistent with ovarian stimulation increasing the risk of EP.

Serum HCG measured in the peri-implantation period predicts IVF cycle outcomes.

The current study assessed the relationship between serum concentrations of human chorionic gonadotrophin (HCG) measured in the peri-implantation period and various outcome measures following blastocyst transfer in IVF cycles. The study group included 767 autologous IVF cycles, each with the transfer of two fresh blastocysts in a 6-year study period, ending 31 December 2009. Outcome measures were ectopic pregnancy, biochemical pregnancy loss, ongoing pregnancy, spontaneous abortion and multiple pregnancy. Peri-implantation serum HCG concentration measured 5 days after blastocyst transfer was highly predictive of these outcome measures. These findings suggest embryonic implantation and developmental fate are largely determined by 5 days after blastocyst transfer and that very early serum HCG measurements may be useful markers of IVF outcome.

Evidence of impaired endometrial receptivity after ovarian stimulation for in vitro fertilization: a prospective randomized trial comparing fresh and frozen-thawed embryo transfers in high responders.

Clinical pregnancy rates of 80% and 65% were observed in cycles using thawed and fresh embryos, respectively, although embryo quality indicators revealed morphologically and numerically inferior embryo cohorts after cryopreservation. Subsequent logistic regression analysis controlled for differences in embryo quality and revealed significantly greater probability of clinical pregnancy with thawed embryos when compared with fresh, suggesting a negative effect of ovarian stimulation on endometrial receptivity.

Evidence of impaired endometrial receptivity after ovarian stimulation for in vitro fertilization: a prospective randomized trial comparing fresh and frozen-thawed embryo transfer in normal responders.

OBJECTIVE: To compare success rates between fresh ETs after ovarian stimulation and frozen-thawed ETs (FET) after artificial endometrial preparation, to compare endometrial receptivity. DESIGN: Randomized, controlled trial. SETTING: Private fertility center. PATIENT(S): There were 53 patients completing fresh blastocyst transfer (fresh group) and 50 patients completing FET (cryopreservation group). All were first-time IVF patients aged <41 years, with cycle day 3 FSH <10 mIU/mL and 8-15 antral follicles. INTERVENTION(S): Randomized to fresh or thawed ET. MAIN OUTCOME MEASURE(S): Clinical pregnancy rate per transfer. RESULT(S): The clinical pregnancy rate per transfer was 84.0% in the cryopreservation group and 54.7% in the fresh group. The implantation rates were 70.8% and 38.9%, respectively. The ongoing pregnancy rates per transfer (at 10 weeks' gestation) were 78.0% and 50.9%, respectively. The attributable risk percentage of implantation failure due to reduced endometrial receptivity in the fresh group was 64.7%. CONCLUSION(S): The clinical pregnancy rate per transfer was significantly greater in the cryopreservation group than in the fresh group. These results strongly suggest impaired endometrial receptivity in fresh ET cycles after ovarian stimulation, when compared with FET cycles with artificial endometrial preparation. Impaired endometrial receptivity apparently accounted for most implantation failures in the fresh group. ClinicalTrials.gov Identifier: NCT00963625.

Comparison of "triggers" using leuprolide acetate alone or in combination with low-dose human chorionic gonadotropin.

This retrospective study of fresh autologous blastocyst transfers in high responders compared ongoing pregnancy rates in cycles that followed trigger with GnRH agonist (GnRHa) alone with standard luteal support, GnRHa alone with enhanced luteal support, or GnRHa with concomitant low-dose hCG (dual trigger). Ongoing pregnancy rates were significantly increased with the dual trigger or with enhanced luteal support, whereas the incidence of clinically significant ovarian hyperstimulation syndrome was 0.0% in the groups receiving only GnRHa and 0.5% (1 of 182) in patients receiving GnRHa with concomitant low-dose hCG.

Efficacy of induced luteinizing hormone surge after "trigger" with gonadotropin-releasing hormone agonist.

The magnitude of the LH surge after GnRH agonist "trigger" was correlated with oocyte yield and maturity and was suboptimal in approximately half of the cycles. A modest reduction in oocyte yield and maturity was observed when the serum level of LH 12 hours after GnRH agonist trigger was less than the median value (52 IU/L), and a dramatic reduction in yield and maturity was observed when that level was less than 12 IU/L.

Embryo cryopreservation rescues cycles with premature luteinization.

OBJECTIVE: To determine whether embryo cryopreservation in cycles with elevated preovulatory P followed by thaw, extended culture, and transfer results in greater ongoing pregnancy rates than fresh blastocyst transfer. DESIGN: Retrospective matched cohort study. SETTING: Private fertility center. PATIENT(S): The study group consisted of 118 consecutive thaws of bipronucleate (2PN) oocytes derived from autologous cycles with elevated preovulatory P, resulting in 95 blastocyst transfers. The control group was selected by matching on the number of 2PN oocytes and patient age and consisted of 118 fresh cycles with elevated preovulatory P, including 108 fresh autologous blastocyst transfers. All patients were <41 years old at the time of stimulation. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Implantation and ongoing pregnancy rates. RESULT(S): The study group had significantly fewer blastocysts per 2PN oocyte than the control group (19.7% vs. 36.8%, respectively) and a significantly greater cancellation rate (19.5% vs. 8.5%, respectively). However, the ongoing pregnancy rate per cycle was significantly higher in the study group than in the control group (56.8% vs. 32.2%, respectively), resulting from greater rates of implantation (56.8% vs. 26.9%, respectively) and of ongoing pregnancy per transfer (70.5% vs. 35.2%, respectively). CONCLUSION(S): In cycles with elevated preovulatory P, the probabilities of implantation and ongoing pregnancy are increased if all 2PN oocytes are cryopreserved and subsequently thawed and cultured to the blastocyst stage before transfer.

Similar ongoing pregnancy rates after blastocyst transfer in fresh donor cycles and autologous cycles using cryopreserved bipronuclear oocytes suggest similar viability of transferred blastocysts.

This retrospective cohort study compared blastocyst transfers in 136 fresh oocyte donor cycles and 69 autologous cycles using blastocysts derived from culture of thawed bipronuclear oocytes, all with oocytes derived from patients or donors less than 35 years old. The autologous cycles and oocyte donor cycles had similar rates of implantation (65.9% vs. 62.1%, respectively) and ongoing pregnancy (79.7% vs. 75.0%, respectively), suggesting that autologous blastocysts transferred after post-thaw extended culture have viability and implantation potential that are comparable with those of blastocysts transferred in fresh oocyte donor cycles.