Day 3 compared with day 2 cryopreservation does not affect embryo survival but improves the outcome of frozen-thawed embryo transfers

The effect of fresh IVF cycle characteristics on frozen embryo transfer (FET) outcomes

Objective

To determine the effect of fresh IVF/ICSI cycles on FET cycle embryo and pregnancy outcomes.

Methods

This retrospective cohort study included data from the medical records of 104 FET cycles performed from January 2014 to December 2016. Embryos were previously vitrified and then thawed for embryo transfer. Statistical significance was established at p<0.05. The main endpoints were FET cycle survival and pregnancy rates.

Results

A total of 104 FET cycles were analyzed for survival; 94 showed good progression and 84 achieved embryo transfers. Patients with secondary infertility achieved significantly higher pregnancy rates - 6/38 (15.8%) vs. 18/46 (39.1%) (p<0.018). Stimulation with FSH/LH resulted in more significant embryo progression, 38/48 (79.2%) vs. 28/46 (60.9%) in the FSH group (p=0.01). Patients who got pregnant from fresh cycles had the highest pregnancy rates in FET cycles (p<0.0001). Lower numbers of frozen embryos correlated with higher pregnancy rates (p=0.048). Embryos frozen on day 2 or 3 had the most significant progression (p<0.0001). Freeze-thaw intervals >12 months yielded higher pregnancy rates, 13/30 (43%), vs. 11/54 (20.4%) (p=0.025).

Conclusion

Patient pregnancy in fresh cycles is a good prognostic factor for FET cycle success. Delaying FET by more than 12 months might result in higher pregnancy rates.

Comparison between two protocols for thawed embryo transfer: natural cycle versus exogenous hormone replacement

INTRODUCTION

There are two most popular protocols for Frozen Embryo Transfer: the natural and the E2&P4 replacement cycles. There is still a controversy whether one is superior over the other.

PURPOSE

To compare the outcome in patient groups undergoing FET following these protocols.

METHODS

About 1235 FET cycles were retrospectively analyzed during a period of 12 years. In 798 cycles (group A), the natural cycle protocol was used, and in 437 cycles (group B), the exogenous E2&P4 administration protocol was used.

RESULTS

The average patient age was 32.11 ± 0.27 years in group A and 32.94 ± 0.19 years in group B (p<0.05). The endometrial thickness was 9.54 ± 0.11 mm and 8.95 ± 0.13 mm in groups A and B, respectively (p<0.001). The peak serum E2 level was 162.51 ± 8.97 pg/mL and 250.78 ± 33.67 pg/mL in groups A and B, respectively (p<0.001). The implantation, clinical pregnancy, and ongoing pregnancy rates in groups A and B were 6.47%, 12.91%, and 10.4% versus 4.26%, 8.47%, and 5.95%, respectively (p<0.05).

CONCLUSIONS

Natural endometrial preparation yields better outcome in compare with exogenous E2&P4 in FET cycles with higher endometrial thickness, implantation, and clinical pregnancy rates.

The outcome of different post-thawed culture period in frozen-thawed embryo transfer cycle

PURPOSE

To study the influence of post-thawed culture (2-4 h and 20-24 h) on the outcome of frozen-thawed embryo transfer (FET) cycle.

METHODS

In this retrospective study, a total of 1,353 patients were undergoing the FET treatment at the reproductive medical center between June 2010 and July 2012. 3,398 frozen-thawed embryos were divided in two study groups, depending on their post-thawed culture period: short culture (2-4 h) group and long culture (20-24 h) group. Groups were compared including clinical pregnancy rate, implantation rate, spontaneous abortion rate, ectopic pregnancy rate, multiple pregnancy rate, live birth rate and birth weight.

RESULTS

When embryos including at least one grade I embryo after thawed transferred, the clinical pregnancy rate, implantation rate, multiple pregnancy rate, abortion rate, ectopic pregnancy rate, live birth rate and birth weight were similar in the short culture group compared with these in the long culture group.

CONCLUSIONS

The outcomes of the two approaches (short culture and long culture) are no different in FET cycles.

Vitrification of day 3 cleavage-stage embryos yields better clinical outcome in comparison with vitrification of day 2 cleavage-stage embryos

The objective of this retrospective study was to determine an optimal time point for vitrification of cleavage-stage human embryos. This study included patients who were undergoing day 2 or day 3 vitrified–warmed cleavage-stage embryo transfer at the In Vitro Fertilization (IVF) Programme of the Shanghai First Maternity and Infant Hospital, China, affiliated to the Tongji University School of Medicine, from April 2010 to March 2012. Intervention was made for the entire cohort of vitrified embryos for poor responder patients so as to avoid severe ovarian hyperstimulation syndrome. Embryo survival rate (SR) after vitrification–warming, implantation rate (IR), and clinical pregnancy rate (CPR) were the main outcome measurements. In total, 380 vitrified–warmed cleavage-stage embryo transfer (VWT) cycles were included. We found that the SR after vitrification and warming for day 2 embryos and day 3 embryos were 92.7% and 92.8%, respectively. For poor ovarian responders, the IR of day 2 and day 3 vitrified–warmed embryos was 6.4% and 13.2%, respectively (P = 0.186). The CPR for day 3 vitrified–warmed embryos was significantly higher than that of day 2 vitrified–warmed embryos (17.6 vs. 4.0 % per transfer cycle, P = 0.036). For patients who had their entire cohort of embryos vitrified to prevent severe ovarian hyperstimulation syndrome (OHSS), the IR and CPR were not significantly different for day 2 and day 3 vitrified–warmed embryo transfer. In conclusion, for vitrified–warmed embryo transfer, cryopreservation of the entire cohort of embryos on day 3 resulted in better clinical outcomes compared with cryopreservation on day 2. Therefore, it is highly recommended that cleavage-stage embryos should be vitrified on day 3, but not on day 2, particularly for poor ovarian responder patients.

Evaluation of embryo transfer time (day 2 vs day 3) after imposed single embryo transfer legislation: when to transfer?

To determine whether the timing of embryo transfer (day 2 or day 3) affects pregnancy outcome in IVF patients, receiving single or double embryo transfer, 380 patients were included in this retrospective study. All patients underwent GnRH antagonist protocol. When stratified by number of transferred embryos, single embryo transfer (SET) patients undergoing a day 2 embryo transfer (ET) had similar biochemical pregnancy (25% vs 20.4%; p > 0.05) and clinical pregnancy (16.6% vs 14.6%; p > 0.05) rates to SET patients that were undergoing a day 3 ET. A similar observation was again noted in double embryo transfer (DET) patients undergoing a day 2 ET, with similar biochemical pregnancy (35% vs 29.8%; p > 0.05) and clinical pregnancy (25% vs 15.5%; p > 0.05) rates to DET patients undergoing a day 3 ET. Women, despite age, number of transferred embryos and ET timing, have similar reproductive outcomes. Shortening or lengthening the duration of in vitro culture provides no obvious benefit.

Influence of post-thaw culture on the developmental potential of human frozen embryos

PURPOSE

Apart from freezing/thawing related cryodamage, several additional factors have been identified as major players in the reduction of success rates after frozen embryo transfers. The post-thaw culture is particularly relevant as it may amplify environmental influences over a stressed embryo. In the present study the influence of the post-thaw culture duration on the implantation and developmental potential of cleavage stage embryos was evaluated.

METHODS

In this retrospective evaluation, that spanned an 8-year period, 631 frozen-thawed embryos were allocated to one of two study groups, depending on their post-thaw culture period: 1) the long (18-24 h), or 2) the short (2-5 h) culture group. Groups were compared regarding implantation rate and live birth rate per embryo transferred. This comparison was corrected for the most common confounding factors such as maternal age at oocyte pick-up, number of transferred embryos, developmental day at freezing, blastomere survival after thawing, catheter used for transfer and year of procedure.

RESULTS

Implantation and live birth rate per embryo transferred were inversely related to the duration of the post-thaw culture, as diminishing this period significantly increased both rates. Moreover, no advantage could be found for a long post-thaw culture period, even for embryos with observed mitotic activity.

CONCLUSION

This retrospective analysis indicates that a short post-thaw culture period is associated with higher implantation and live birth rates per embryo. This study supports selection of frozen-thawed embryos strictly based on blastomere cryosurvival and raises the hypothesis that environmental factors may have an important role on embryo implantation and developmental potential during post-thaw culture.

Correlation between embryological factors and pregnancy rate: development of an embryo score in a cryopreservation programme

PURPOSE

To establish which embryo parameters, in frozen thawed embryo transfers, have the highest prognosis value in the establishment of pregnancy. The relative importance of different embryo parameters is used to develop an embryo score.

METHODS

Retrospective analysis of the implantation rate in 356 frozen/thawed single embryo transfers. A logistic regression model is used to establish an embryo score.

RESULTS

A direct correlation is established between the implantation rate and fresh embryo development (number of blastomeres and their symmetry), survival rate after thawing and mitosis resumption after overnight culture.

CONCLUSIONS

An embryo score is developed to determine the implantation potential of frozen/thawed embryos.

[Views of each member of an Assisted Reproductive Technologies centre on the embryo transfer procedure]

The embryo transfer (ET) is probably the key step of Assisted Reproductive Technologies (ART), end point of the collaboration of a multidisciplinary clinical team and an infertile couple. Thus, a perfect knowledge of available data regarding ET is required to optimize the results of ART. Indeed, numerous published studies demonstrate the impact of defined parameters onto the effectiveness of ET procedure. The aim of this study is to provide views of physicians dealing with ART, i.e. endocrinologist, ultrasound scan specialist, surgeon and biologist to put in perspective questions and answers about ET.