Higher clinical pregnancy rates from frozen-thawed blastocyst transfers compared to fresh blastocyst transfers: a retrospective matched-cohort study

Vitrification of human blastocysts for couples undergoing assisted reproduction: an updated review

Over the past 40 years there has been a worldwide critical change in the field of assisted reproduction technology (ART), leading to the increased application of single blastocyst transfer, which is extremely important to avoid the risks of multiple pregnancy and associated complications for both mother and babies. Indeed, advancements in ART over the last few decades have been obtained thanks to several improvements, including ovarian stimulation, embryo culture conditions and, of course, progress in cryopreservation methods, especially with the application of vitrification. The ability to cryopreserve human embryos has improved significantly with vitrification compared to the initially adopted slow-freezing procedures. Since the introduction of vitrification, it has become the gold standard method to effectively cryopreserve human blastocysts. However, some new protocols are now being explored, such as the short warming procedure and even shorter exposure to the equilibration solution before vitrification, which seem to provide optimal results. Therefore, the main aim of the current narrative review, will be to illustrate the benefit of vitrification as an effective method to cryopreserve the human blastocyst and to illustrate new protocols and variations which in future may increase the performance of vitrification protocols.

Age-related increase in live-birth rates of first frozen thaw embryo versus first fresh transfer in initial assisted reproductive technology cycles without PGT

BACKGROUND

The landscape of assisted reproductive technology (ART) has seen a significant shift towards frozen-thawed embryo transfers (FET) over fresh transfers, driven by technological advancements and clinical considerations. This study aimed to compare live birth outcomes between primary FET and fresh transfers, focusing on cycles without preimplantation genetic testing (PGT), using United States national data from the SART CORS database spanning from 2014 to 2020.

METHODS

We performed a retrospective cohort study of autologous first ART cycles without PGT comparing primary embryo transfer (frozen thaw vs. fresh) success rates from the 2014-2020 SARTCORS database. Live-birth rates (LBR) and cumulative live-birth rates (CLBR) were compared between first FET versus first fresh embryo transfer from an index retrieval. Multivariate logistic regression (MLR) determined association between live birth outcomes and method of transfer. In a subsequent sub-analysis, we compared these two embryo transfer methods among patients with either diminished ovarian reserve (DOR) or male factor infertility.

RESULTS

228,171 first ART cycles resulted in primary embryo transfer. 62,100 initial FETs and 166,071 fresh transfers were compared. Initial FETs demonstrated higher LBR and CLBR compared to fresh transfers (LBR 48.3% vs. 39.8%, p < 0.001; CLBR 74.0% vs. 60.0%, p < 0.0001). MLR indicated greater chances of live birth with FET across all age groups, with adjusted odds ratio (aOR) of live-birth incrementally increasing with advancing age groups. For DOR cycles, LBR and CLBR were significantly higher for FET compared to fresh (33.9% vs. 26.0%, p < 0.001, 44.5% vs. 37.6%, p < 0.0001), respectively. MF cycles also demonstrated higher LBR and CLBR with FET (52.3% vs. 44.2%, p < 0.001, 81.2% vs. 68.9%, p < 0.0001), respectively. MLR demonstrated that in DOR cycles, initial FET was associated with greater chance of live birth in age groups ≥ 35yo (p < 0.01), with aOR of live birth increasingly considerably for those > 42yo (aOR 2.63, p < 0.0001).

CONCLUSIONS

Overall LBR and CLBR were greater for first FET than fresh transfers with incremental increases in odds of live birth with advancing age, suggesting the presence of a more favorable age-related change in endometrial receptivity present in frozen-thawed cycles. For both DOR and MF cycles, LBR and CLBR after primary transfer were greater for first FET than fresh. However, this was particularly evident in older ages for DOR cycles. This suggests that supraphysiologic stimulation in older DOR cycles may be detrimental to endometrial receptivity, which is in part corrected for in FET cycles.

Pregnancy Outcomes for Day 5 Versus Day 6 Single Frozen-thawed Blastocyst Transfer with Different Qualities of Embryos: A Large Matched-cohort Study

OBJECTIVE

This study aimed to determine whether the day of blastocyst expansion affects pregnancy outcomes in frozen-thawed blastocyst transfer (FBT) cycles.

METHODS

A retrospective match-cohort study was conducted. Patients who underwent blastocyst transfer in frozen-thawed cycles at day 5 or 6 were matched for potential confounding factors. A total of 2207 matched pairs of FBT cycles were included from January 2016 to December 2019 in our Reproductive Medicine Center.

RESULTS

The clinical pregnancy rate (CPR) and live birth rate (LBR) were significantly increased in day 5 blastocyst transfers when compared to day 6 blastocyst transfers, in terms of the same embryo quality. For FBT cycles with good-quality embryo, the CPR at day 5 and 6 was 61.30% and 57.56%, respectively (P=0.045), and the LBR was 44.79% and 36.16%, respectively (P<0.001). For FBT cycles with poor-quality embryo, the CPR at day 5 and 6 was 48.61% and 40.89%, respectively (P=0.006), and the LBR was 31.71% and 25.74%, respectively (P=0.019). The CPR for FBT cycles with good-quality embryo was statistically higher at day 6 than that at day 5 with poor-quality embryo transferred (57.56% vs. 48.61%, P=0.001). Maternal age, anti-Müllerian hormone (AMH), endometrial thickness, embryo quality, and the day of blastocyst expansion were independently correlated with the CPR and LBR. The FBT cycles at day 5 had significantly higher CPR (adjusted odds ratio [OR]=1.246, 95% confidence intervals [CI]: 1.097-1.415, P=0.001) and LBR (adjusted OR=1.435, 95% CI: 1.258-1.637, P<0.001) than those at day 6.

CONCLUSION

The embryo quality is the primary indicator for FBT cycles. Day 5 blastocysts should be preferred when the quality of embryo at day 5 is the same as that at day 6.

Prolonging the time of progesterone supplementation to improve the pregnancy outcomes of single day 6 blastocyst transfer in frozen-thawed cycles: study protocol for a randomized controlled trial

BACKGROUND

Infertility is one of the most important and underappreciated reproductive health problems in developing countries. Currently, in vitro fertilization and embryo transfer is the most effective treatment strategy for infertility. In a frozen-thawed cycle, single-blastocyst transfer can not only ensure relatively higher pregnancy and live birth rates but also effectively reduce the risk of maternal and neonatal complications. In frozen-thawed cycles, progesterone is initiated to promote the final phase of endometrial preparation prior to embryo transfer. However, the optimal duration of exposure to progesterone has remained inconclusive. Therefore, we designed a randomized controlled trial (RCT) to compare the effects of different prolonged progesterone transformation times (P+6 and P+7) on the pregnancy outcomes of D6 single blastocyst transfer in a frozen-thawed cycle.

METHODS

This is a single-center, prospective, randomized controlled clinical trial involving 900 patients with single blastocyst transfer in the frozen-thawed cycle, aged from 20 to 38 years, with less than three transfers, and with HRT-cycle single D6 blastocyst transfer in the current cycle. Participants will be randomly assigned (1:1) into two parallel groups: the transfer of day 6 blastocysts on the 7th day of progesterone supplementation and the transfer of day 6 blastocysts on the 6th day of progesterone supplementation. The primary outcome measure is the clinical pregnancy rate. Secondary outcome measures include the miscarriage rate and live birth rate.

DISCUSSION

This is the first randomized controlled trial to compare the transfer of day 6 blastocysts on the 6th and 7th day of progesterone supplementation. The results of this study will provide evidence for whether to prolong the duration of exposure to progesterone prior to embryo transfer.

TRIAL REGISTRATION

ClinicalTrials.gov, ID: NCT04938011. Registered on 19 June 2021.

Thawing day 3 embryos and culturing to day 5 may be a better method for frozen embryo transfer

PURPOSE

Does thawing cleavage embryos and culturing them for transfer as blastocysts improve pregnancy and perinatal outcomes compared to transferring thawed blastocysts?

METHODS

Retrospective, observational cohort study performed at two assisted reproductive technology centers, 2014 to 2020. A total of 450 patients with 463 thawed embryo transfer cycles were divided into 2 groups according to the embryonic developmental stage at cryopreservation and transfer: 231 thawed blastocysts (day 5 group) and 232 thawed cleavage embryos that were cultured for 2 days and transferred as blastocysts (day 3-5 group). The two groups were compared for demographics, routine parameters of IVF treatment, pregnancy rates, and perinatal outcomes.

RESULTS

Multivariable logistic regression analysis for ongoing pregnancy and delivery demonstrated that the day 3-5 group had a greater likelihood of achieving ongoing pregnancy and delivery compared to the day 5 group (OR 1.58, 95%CI 1.062-2.361, p = 0.024). Perinatal outcomes were comparable between the three groups.

CONCLUSION

Our results support culturing post-thaw cleavage embryos for 2 days and transferring them as blastocysts to increase chances of ongoing pregnancy and delivery.

Effects of immediate versus delayed frozen embryo transfer in high responder patients undergoing freeze-all cycles

Background

Frozen embryo transfer (FET) can greatly improve the pregnancy outcomes for high responder patients. However, it is not known whether the timing of FET is a risk factor on pregnancy outcomes in high responder patients undergoing freeze-all cycles.

Methods

A retrospective cohort study to compare the pregnancy outcomes of the immediate and delayed FET groups in high responder patients undergoing freeze-all cycles. The two groups were defined as that FET took place either within the first menstrual cycle following oocyte retrieval or afterwards. Propensity score matching was used to make the potential risk factors of the two groups comparable. Multivariable regression analysis was used to study the effect of the timing of FET on pregnancy outcomes in the entire cohort and propensity score-matched cohort, even in different controlled ovarian hyperstimulation protocol cohorts as subgroup analysis.

Results

We obtained 1130 patients in immediate FET group and 998 patients in delayed FET group, and the average age of the two groups were 30.30 and 30.63. We showed that the immediate FET group were equivalent to delayed FET group in the entire cohort [clinical pregnancy rate (CPR), 61.0% versus 63.4%, adjusted odd ratio (OR), 0.939, 95% confidence interval (CI), 0.781–1.129; spontaneous abortion rate (SAR), 10.1% versus 12.6%, adjusted OR, 0.831, 95% Cl (0.628–1.098); live birth rate (LBR), 49.9% versus 49.2%, adjusted OR, 1.056, 95% Cl (0.883–1.263)]. The same results were obtained by χ² test in the propensity score-matched cohort (CPR, 60.5% versus 63.5%; SAR, 11.6% versus 12.3%; LBR, 48% versus 49.3%) (P > 0.05). Subgroup analysis indicated that pregnancy outcomes of immediate FET were no difference to delayed FET in gonadotropin-releasing hormone agonist (GnRH-a) protocol (P > 0.05). The SAR of the immediate FET group were lower than that of the delayed FET group in GnRH antagonist protocol (adjusted OR, 0.645, 95% CI, 0.430–0.966) (P < 0.05), no differences were observed in CPR and LBR (P > 0.05).

Conclusions

The pregnancy outcomes of immediate FET were no difference to delayed FET in high responder population undergoing freeze-all cycles.

Vitrification of the human embryo: a more efficient and safer in vitro fertilization treatment

Cryopreservation has become a central pillar in assisted reproduction, reflected in the exponential increase of "freeze all" cycles in the past few years. Vitrification makes it possible to cool and warm human eggs and embryos with far less cryo-damage than 'slow-freeze' and allows nearly intact survival of embryos with very high survival rates for eggs as well. This has resulted in a complete transformation how we manage treatment for in vitro fertilization patients. Fresh transfers can be avoided without compromising outcomes, and in fact, cumulative pregnancy/delivery rates may be improved by performing sequential elective "frozen" single embryo transfers. Some recent evidence suggests that previously vitrified embryos give better perinatal outcomes than fresh embryo transfers. Frozen embryo transfer, especially when coupled with preimplantation genetic testing allows for highly efficient single embryo transfers that translate to more singleton and therefore safer pregnancies, as well as healthier babies. Additionally, vitrification has also opened new options for patients, most notably fertility preservation (through oocyte cryopreservation), and donor egg banking.

The indicator of clinical outcomes for patients with heterotopic pregnancy following in-vitro fertilization with embryo transfer

OBJECTIVE

To explore the early predictors for pregnancy outcomes in patients with heterotopic pregnancy (HP) following in-vitro fertilization with embryo transfer (IVF-ET).

MATERIAL AND METHODS

This retrospective study reviewed 81 patients with HP following IVF-ET in our institution between January 2003 and September 2017. The relationships between clinical outcomes and general characteristics, sonographic features and different management options were analyzed by logistic regression analysis.

RESULTS

The gestational age at the time of diagnosis was 50.9 ± 12.3 days. Among these cases, 76 were accurately diagnosed by TVS, 1 was misdiagnosed as adnexal torsion by TVS, and 4 were confirmed to have IUPs after the surgical treatment. Hence, the sensitivity of TVS for detecting HP was 93.8% (76/81). However, forty-seven patients (58.0%) had suspected HP when they underwent the initial TVS. Among these patients, live births occurred for 60 patients, 11 of whom delivered preterm. The miscarriage rate was 58.3% (14/24) for patients without IUP cardiac activity at HP diagnosis, and 12.3% (7/57) for patients with IUP cardiac activity; a significant correlation was identified (χ² = 18.651, P < 0.001). Additionally, the abortion rate of patients following fresh non-donor embryo was higher than patients after frozen-thawed embryo (χ² = 10.437, P = 0.001). Further by logistic regression analysis, patients following frozen-thawed embryo and an IUP with cardiac activity at HP diagnosis were identified as two independent factors of pregnancy outcome. (OR = 0.060, 95%CI = 0.008-0.471, P = 0.007; OR = 0.010, 95%CI = 0.001-0.124, P<0.001).

CONCLUSIONS

Patients following frozen-thawed embryo and an IUP with cardiac activity at HP diagnosis could be the independent predictors for a favorable prognosis.

Frozen blastocyst embryo transfer vs. frozen cleavage-stage embryo transfer in couples with recurrent implantation failure: a cohort study

The objective of this prospective cohort study was to investigate whether cryopreservation of cleavage or blastocyst stage embryos improves in vitro fertilization outcomes in recurrent implantation failure (RIF) patients. The study comprised 575 patients who were allocated to receive either single frozen/thawed blastocyst-stage transfer (SBT) or frozen/thawed double-cleavage-stage embryo transfer (DET). The clinical pregnancy rate, implantation rate, and ongoing pregnancy rate were higher in the SBT group compared with the DET group (41.15% vs. 27.11%, p < 0.001; 41.15% vs. 19.28%, p < 0.001; 40.03% vs. 25.9%, p < 0.001), but the miscarriage rate did not differ between the two groups. It was concluded that frozen/thawed SBT could be a preferred strategy for RIF patients.

Frozen blastocyst transfer reduces incidence of ectopic pregnancy compared with fresh blastocyst transfer: a meta-analysis

BACKGROUND

Ectopic pregnancy (EP) is the main cause of maternal death during early pregnancy. Blastocyst transfer (BT) reduces EP rates compared with cleavage stage embryo transfer (ET), and frozen ET reduces EP rates compared with fresh ET. However, data comparing the EP rate of fresh BT and frozen BT are limited. The objective of this meta-analysis was to determine whether frozen BT decreases the EP rate compared with fresh BT.

MATERIALS AND METHODS

PUBMED, EMBASE, and Cochrane Library databases were searched for papers with no limitation on language and publication year. A systemic literature search identified 14 studies which met the inclusion criteria for further analysis. EP rate is our only outcome measure. All statistical analyses were carried out using RevMan software [version 5.3]. Random effects models were chosen to calculate the odds ratio (OR).

RESULTS

Fourteen retrospective studies (n = 251,762 cycles) were finally analyzed, including 154,214 and 97,548 cycles undergoing fresh and frozen BT, respectively. Compared with fresh BT, the frozen BT was associated with an decrease in EP rate [OR = 1.79; 95% confidence interval (CI) = 1.37-2.34, heterogeneity was 71%], the EP rate was 1.74% (2683/154,214 pregnancies) for fresh BT and 0.97% (949/97,548 pregnancies) for frozen BT. The number of embryos transferred in subgroup analysis found that the incidence of EP in frozen BT is lower than fresh BT (OR = 1.62; 95% CI = 1.38-1.91), the EP rate was 1.2% (206/16,610 pregnancies) for one fresh BT and 0.8% (153/19,569 pregnancies) for one frozen BT, also the EP rate was 1.9% (78/4043 pregnancies) for two fresh BT and 1.1% (19/1790 pregnancies) for two frozen BT.

CONCLUSIONS

Our meta-analysis found that frozen BT was associated with an decrease in EP rate compared with fresh BT in IVF/ICSI patients. We also found that a single frozen BT is the better choice as a method to reduce the incidence of EP.

Single best euploid versus single best unknown-ploidy blastocyst frozen embryo transfers: a randomized controlled trial

PURPOSE

This paper aims to investigate the efficacy of IVF with preimplantation genetic testing for aneuploidy (PGT-A), using only best-scoring blastocysts from young (≤ 35 years) infertile patients undergoing single blastocyst frozen embryo transfers (FET).

METHOD

In this randomized controlled trial (RCT) registered 29 March 2017, 302 infertile patient-couples eligible to participate underwent autologous ICSI blastocyst freeze-all cycles. Two-hundred and twenty patient-couples satisfied the inclusion criteria (i.e., female age ≤ 35 years, two-day 5 ≥ 2BB blastocysts) and were randomized to either the PGT-A (PGT-A group, n = 109) selection arm or morphology score (morphology group, n = 111) selection arm. In both arms, the highest ranking (by morphological score) blastocysts were selected for FET.

RESULTS

Of the 109 best-scoring blastocysts that underwent PGT-A, 80 were predicted to be euploid (73.4%) and were transferred in FET (euploid subgroup). There was no statistical difference in LB rate between the euploid subgroup and morphology group (56.3% vs 58.6%, odds ratio 0.91 (95% CI 0.51-1.63), p = 0.750). In a multiple logistic regression, the transfer of euploid blastocysts was not found to be a significant predictor of LB when adjusting for female age, infertility duration, antral follicle count, and blastocyst quality, with the independent odds expressed as 0.91 (95% CI 0.50-1.66, p = 0.760).

CONCLUSION

In young (≤ 35 years) infertile patients with at least two ≥ 2BB blastocysts, PGT-A blastocyst selection does not result in an enhanced LB rate, with the evidence suggesting that the effectivity of PGT-A may be limited by the effectivity of TE biopsy.

TRIAL REGISTRATION

ClinicalTrials.gov ID: NCT03095053.

Effect of next-generation sequencing in preimplantation genetic testing on live birth ratio

The present study analysed live birth ratios in frozen embryo transfer (FET) cycles where embryo ploidy status was determined with preimplantation genetic testing (PGT) using next-generation sequencing (NGS). PGT was performed on trophectoderm cells biopsied at the blastocyst stage. The present prospective cohort study included 112 women undergoing frozen embryo transfer, with NGS PGT. The control group consisted of 85 patients who underwent the IVF procedure with FET planned for a subsequent cycle. The live birth rate per cycle was higher by ~18.5 percentage points in the investigated compared with control group (42.0% vs 23.5% respectively; P = 0.012). The differences between the study and control groups were also significant for clinical pregnancy (42.0% vs 23.5% respectively; P = 0.012), implantation (41.2% vs 22.2% respectively; P = 0.001) and pregnancy loss rates (9.6% vs 28.6% respectively; P = 0.027). The results show that PGT NGS is a useful method for embryo selection and it may be implemented in routine clinical practice with propitious results.

Artificial cryopreserved embryo transfer cycle success depends on blastocyst developmental rate and progesterone timing

This retrospective cohort analysis compared the developmental competence of cryopreserved day-4 and 5 blastocysts, and investigated the effect of progesterone administration duration on the success of artificial frozen embryo transfers. Between October 2015 and March 2016, 868 intracytoplasmic sperm injection blastocyst cryo-all cycles were carried out, with 586 subsequently undergoing frozen embryo transfer. Of these, 243 were day-5 single blastocyst transfers (SBT) and 152 were day-4 SBT. Day-4 blastocysts were transferred on day-5 progesterone (day-4 group) and day-5 blastocysts were transferred on day-5 (short-protocol day-5 sub-group, n = 104) or day-6 (standard-protocol day-5 sub-group, n = 139) progesterone. Although more blastocysts were transferred in the standard-protocol day-5 sub-group (P = 0.009), pregnancy, clinical pregnancy and live birth rates were similar to those of the day-4 group, but were significantly lower in the short-protocol day-5 sub-group (P = 0.004, P = 0.008 and P = 0.02 respectively). For optimal outcomes, day-4 blastulating embryos should be prioritized for transfer on day 5 of progesterone and for day-5 blastocysts, transfer should be delayed by 1 day. The retrospective analysis and lack of adjustment for all known confounding variables limit the study.

Vitrified-warmed blastocyst transfer on the 5th or 7th day of progesterone supplementation in an artificial cycle: a randomised controlled trial

Prospective studies comparing different durations of progesterone supplementation before transfer of vitrified-warmed blastocysts in an artificial cycle are lacking. However, in oocyte donation programmes, the sporadic available evidence demonstrates considerable differences in clinical pregnancy rates according to the duration of progesterone administration. This randomised controlled trial (RCT), included 303 patients undergoing a frozen-thawed embryo transfer (FET) of one or two vitrified-warmed blastocyst(s) in an artificial cycle. Randomisation was performed when the endometrial thickness reached ≥7 mm after oestrogen supplementation. One hundred and fifty two patients in group A received 7 d of vaginal micronised progesterone tablets and 151 patients in group B received 5 d of micronised vaginal progesterone before FET. No differences were seen in clinical pregnancy rate between both groups: 42/152 (27.6%) in group A versus 49/151 (32.5%) in group B. Although no statistically significant difference was observed in clinical pregnancy rates, our study was powered to detect an absolute difference of 16%. In this regard, we cannot exclude that smaller, clinically relevant differences might exist and our study did not have the power to detect this. Patients were also not blinded for the intervention, causing a potential bias.

Frozen embryo transfer can be performed in the cycle immediately following the freeze-all cycle

PURPOSE

In this study, we investigated whether the time interval between oocyte retrieval and frozen embryo transfer (FET) affected the live birth (LB) rates of human segmented-IVF cycles.

METHOD

A total of 1338 ICSI freeze-all cycles were performed between February 2015 and January 2016, with 1121 FET cycles being retrospectively analyzed. All vitrified-warmed blastocyst transfers were performed in artificial FET cycles, using gonadotropin-releasing hormone (GnRH) agonist downregulation and oral estrogen endometrial preparation. The primary outcome measure was LB. Cycles were investigated in oocyte retrieval-to-FET interval groups of 32-46, 47-61, 62-76, 77-91, and ≥ 92 days, with the 47-61-day group used as the reference group.

RESULTS

There were no significant differences in LB rates between the groups in the overall analysis, as well as, in sub-analyses investigating LB in terms of single blastocyst transfer (SBT), trigger type (GnRH agonist, triggers including hCG), oocyte number (≤ 5 and ≥ 15), and maternal age (> 35 years).

CONCLUSION

The present study showed that it is feasible to perform transfers 36 days after oocyte retrieval and that delaying FET in freeze-all beyond the cycle immediately following oocyte retrieval does not increase LB rates.

The effect of frozen-thawed embryo transfer performed concurrently with hysteroscopy on the reproductive outcomes during assisted reproductive treatments

The uterine environment is vital to the successful conception; recently, hysteroscopy was used to remove uterine anomalies in patients undergoing assisted reproductive treatments in combination with a “freeze-all” strategy. However, the rapid recurrence of uterine anomalies impose a negative impact on pregnancy. A possible way to avoid this issue is to implement frozen-thawed embryo transfer (FET) as soon as possible. Thus, we sought to investigate the impact of performing FET concurrently with hysteroscopy in the same mense on the pregnancy outcome. Patients enrolled were divided into two groups: group 1 (n = 272, FET in this mense) and group 2 (n = 251, FET in the next mense). There were no differences in the clinical pregnancy rate (55.15% vs. 53.78%), implantation rate (39.32% vs. 37.2%), spontaneous miscarriage rate (10% vs. 8.89%), or live birth rate (45.96% vs. 45.02%) when comparing the two groups. Binary logistic regression indicated maternal age was negatively associated with the live birth rate, while FET following hysteroscopy in the same mense had no adverse effects on the live birth rate. Our data indicate performing FET concurrently with hysteroscopy in the same menstrual cycle does not impair the pregnancy outcomes, but additional studies with larger populations are needed to confirm these results.

Deferred Frozen Embryo Transfer: What Benefits can be Expected from this Strategy in Patients with and without Endometriosis?

Progress with cryopreservation techniques have enabled development of the deferred frozen-thawed embryo transfer (DET) strategy as an alternative to relying on fresh embryo transfers.

With DET, the entire embryo cohort is cryopreserved, and embryo transfer is then performed in a subsequent cycle that takes place separately from the controlled ovarian stimulation (COS).

Initially developed to limit the risk of ovarian hyperstimulation syndrome that occurs with high responders, this strategy has been applied extensively with other populations in an effort to improve implantation rates. The assumption is that COS, which is essential for in vitro fertilization/intra cytoplasmic sperm injection (IVF/ICSI) procedures to obtain a multi-follicular development, could have a detrimental impact on the endometrium as a result of greatly elevated levels of steroids. It is currently not clear whether the DET strategy can be generally applied to all women requiring an IVF/ICSI procedure.

The objectives of this literature review regarding DET, were hence: (i) to present the scientific background that contributed to extensive adoption of this technique, (ii) to detail the pregnancy outcomes and potential obstetric and neonatal consequences, (iii) to report on its ability to prevent risks induced by COS, and (iv) to propose indications for the DET strategy in clinical practice.

GnRH agonist administration prior to embryo transfer in freeze-all cycles of patients with endometriosis or aberrant endometrial integrin expression

Prolonged gonadotrophin-releasing hormone agonist (GnRHa) administration before IVF with fresh embryo transfer to patients with endometriosis or aberrant endometrial integrin expression (-integrin) improves outcomes but may suppress ovarian response and prevents elective cryopreservation of all embryos. This retrospective cohort pilot study evaluates freeze-all cycles with subsequent prolonged GnRHa before embryo transfer in these populations. Patients from 2010 to 2015 who met inclusion criteria and received a long-acting GnRHa every 28 days twice before FET were evaluated. A subset underwent comprehensive chromosomal screening (CCS) after trophectoderm biopsy. Three groups were identified: Group 1: + CCS, +endometriosis (20 patients, 20 transfers); Group 2: +CCS, -integrin (12 patients, 13 transfers); Group 3: no CCS, +endometriosis or -integrin (10 patients, 12 transfers); Group 4: all transfers after CCS for descriptive comparison only (n = 2809). Baseline characteristics were similar among Groups 1-3 except that the mean surgery to oocyte aspiration interval was longer for Group 1 than Group 3. Implantation and ongoing pregnancy rates were statistically similar among the three groups and compared favourably to Group 4. A non-significant trend towards improved outcomes was noted in Group 1. Prolonged GnRHa after freeze-all in these patients avoids excessive ovarian suppression and results in excellent outcomes.

Embryo stage of development is not decisive for reproductive outcomes in frozen-thawed embryo transfer cycles

Objective

To evaluate if the outcomes of IVF/ICSI in frozen-thawed embryo transfer and fresh embryo transfer cycles differ in relation to cleavage and blastocyst stages.

Methods

Retrospective cohort study to compare IVF/ICSI outcomes between fresh embryo transfer and frozen-thawed embryo transfer cycles, according to the stage of embryo development. Analysis was carried out on 443 consecutive embryo transfer cycles performed between January 1st and December 31st, 2014. Women aged up to 38 and submitted to embryo transfer cycles with fresh (n = 309) or frozen-thawed (n = 134) embryos at a private center for assistance in human reproduction were considered for analysis. Results in each group were stratified according to the stage of embryo development: cleavage stage and blastocyst stage. Main outcome measures were implantation rate, clinical pregnancy rate, ongoing pregnancy rate and live birth rate per cycle.

Results

In the fresh embryo transfer group, for cleavage stage versus blastocyst stage, respectively, implantation rates were 22% and 47% (p = 0.0005); clinical pregnancy rates were 34% and 64% (p = 0.0057); the ongoing pregnancy rates were 30% and 61% (p = 0.0046) and live birth rates were 28% and 55% (p = 0.0148). There were no significant differences in the rates between cleavage and blastocyst stages in the frozen-thawed group, neither between fresh and frozen-thawed cleavage embryo transfers nor between fresh and frozen-thawed blastocyst transfers.

Conclusion

Our results confirm that blastocyst transfer is better than cleavage stage in fresh embryo transfer cycles. In frozen-thawed cycles, cleavage or blastocyst stages seem to offer similar reproductive outcomes.

Optimal embryo transfer strategy in poor response may include freeze-all

PURPOSE

In this retrospective cohort study, we investigated the best embryo transfer strategy in ICSI cycles with ≤4 oocytes collected at oocyte retrieval.

METHODS

Women who underwent antagonist co-treatment COS for ICSI treatment between January 2010 and December 2015 at a private ART clinic (N = 2263). Eight hundred seventy-nine women (group 1) had ≤4 oocytes collected at oocyte retrieval, of whom 645 (group A) had cleavage stage embryo transfer (ET), and 234 (group B) had blastocyst ET. One thousand three hundred eighty-four women (group 2) had 10-15 oocytes collected at oocyte retrieval, of whom 676 (group C) had cleavage stage ET, and 708 women (group D) had blastocyst ET. Blastocyst vitrification was performed using the Cryotop method and FET using artificial cycles.

RESULTS

In group 1, the cancellation rate was significantly lower in group A (25.2 vs 38 %). The pregnancy rate (PR), clinical PR, implantation rate (IR), and live birth rate (LBR) per ET and per oocyte retrieval were all lower in group A. The clinical PR, IR, and LBR per ET of vitrified-warmed blastocyst ET were significantly the highest. In group 2, the cycle cancellation rate was significantly lower in group C (3.5 vs 13.4 %). The PR, clinical PR, and IR per ET and per oocyte retrieval were all lower in group C. The LBR per ET was significantly lower, but the LBR per oocyte retrieval was not significantly lower in group C. Again, the PR, clinical PR, and IR per ET of vitrified-warmed blastocyst ET were significantly the highest.

CONCLUSIONS

Day 5 ET strategy has been reserved for normal or high responders. The improved pregnancy outcomes from blastocyst culture and cryopreservation may challenge ART to extend this benefit to poor responders.

Outcomes of elective cryopreserved single or double embryo transfers following failure to conceive after fresh single embryo transfer

The main adverse effect of IVF is the high multiple pregnancy rate resulting from the transfer of two or more embryos. The objective was to evaluate pregnancy rates in infertile women with a good prognosis who failed to conceive in a fresh elective single embryo transfer (eSET) and had a second cycle with elective double vitrified-warmed embryo transfer (eDFET) compared with elective single vitrified-warmed embryo transfer (eSFET). A total of 142 intracytoplasmic sperm injection cycles using a conventional protocol were evaluated. Good-prognosis patients underwent eSET in a fresh cycle, and those who failed to conceive underwent a second vitrified-warmed embryo transfer: eDFET (n = 102) or eSFET (n = 40). Embryos were transferred and vitrified on day 5 of development. Patients who received eDFET had fewer implantations (30.9%) than eSFET (52.5%; P = 0.004); pregnancy rates were similar (eDFET: 35.3%, eSFET: 42.5%). Patients with the eSFET had one monozygotic twin (5.9%), and 22.2% of eDFET patients had multiple pregnancies. Patients with a good prognosis who failed to conceive in the first fresh eSET did not have an advantage when receiving eDFET in the second cycle, as pregnancy rates were similar; 22.2% of patients in the eDFET group had multiple pregnancies.

Concurrent oocyte retrieval and hysteroscopy: a novel approach in assisted reproduction freeze-all cycles

In this matched-controlled study (n = 300), the effect of hysteroscopic surgery performed concurrently with oocyte retrieval on the reproductive outcomes of intracytoplasmic sperm injection (ICSI) freeze-all cycles was investigated in patients screened for intrauterine anomalies. Conventionally, hysterscopic surgery is performed in a different cycle from IVF, delaying treatment completion and increasing patient anxiety. One hundred and fifty patients who had hysteroscopic surgery concurrently with oocyte retrieval (hysteroscopy group) in ICSI freeze-all cycles were matched according to age and oocyte number with 150 ICSI freeze-all cycles, in which the patients required no hysteroscopy (control group). In the hysteroscopy group, hysteroscopy was performed for diagnostic (n = 5) and therapeutic (n = 145) purposes. Blastocyst culture and Cryotop vitrification was performed in both groups. Frozen embryo transfer (FET) was successfully performed in the hysteroscopy group from 35 days after oocyte retrieval. No significant differences were observed for implantation, pregnancy, clinical pregnancy and early pregnancy loss rates in the hysteroscopy and control groups (48.9%, 72.0%, 61.3% and 14.8% versus 48.3%, 75.3%, 64.7% and 14.3%, respectively). Performing hysteroscopic surgery concurrently with oocyte retrieval in a segmented-IVF programme has no negative impact on reproductive outcomes, increases efficiency, and provides patients with low-risk treatment.