Outcome Analysis of Day-3 Frozen Embryo Transfer v/s Fresh Embryo Transfer in Infertility: A Prospective Therapeutic Study in Indian Scenario

Fresh versus frozen embryo transfers in assisted reproduction

BACKGROUND

In vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI) treatments conventionally consist of a fresh embryo transfer, possibly followed by one or more cryopreserved embryo transfers in subsequent cycles. An alternative option is to freeze all suitable embryos and transfer cryopreserved embryos in subsequent cycles only, which is known as the 'freeze all' strategy. This is the first update of the Cochrane Review on this comparison.

OBJECTIVES

To evaluate the effectiveness and safety of the freeze all strategy compared to the conventional IVF/ICSI strategy in women undergoing assisted reproductive technology.

SEARCH METHODS

We searched the Cochrane Gynaecology and Fertility Group Trials Register, CENTRAL, MEDLINE, Embase, PsycINFO, CINAHL, and two registers of ongoing trials from inception until 23 September 2020 for relevant studies, checked references of publications found, and contacted study authors to obtain additional data.

SELECTION CRITERIA

Two review authors (TZ and MZ) independently selected studies for inclusion, assessed risk of bias, and extracted study data. We included randomised controlled trials comparing a 'freeze all' strategy with a conventional IVF/ICSI strategy including a fresh embryo transfer in women undergoing IVF or ICSI treatment.

DATA COLLECTION AND ANALYSIS

The primary outcomes were cumulative live birth rate and ovarian hyperstimulation syndrome (OHSS). Secondary outcomes included effectiveness outcomes (including ongoing pregnancy rate and clinical pregnancy rate), time to pregnancy and obstetric, perinatal and neonatal outcomes.

MAIN RESULTS

We included 15 studies in the systematic review and eight studies with a total of 4712 women in the meta-analysis. The overall evidence was of moderate to low quality. We graded all the outcomes and downgraded due to serious risk of bias, serious imprecision and serious unexplained heterogeneity. Risk of bias was associated with unclear blinding of investigators for preliminary outcomes of the study during the interim analysis, unit of analysis error, and absence of adequate study termination rules. There was an absence of high-quality evidence according to GRADE assessments for our primary outcomes, which is reflected in the cautious language below. There is probably little or no difference in cumulative live birth rate between the 'freeze all' strategy and the conventional IVF/ICSI strategy (odds ratio (OR) 1.08, 95% CI 0.95 to 1.22; I2 = 0%; 8 RCTs, 4712 women; moderate-quality evidence). This suggests that for a cumulative live birth rate of 58% following the conventional strategy, the cumulative live birth rate following the 'freeze all' strategy would be between 57% and 63%. Women might develop less OHSS after the 'freeze all' strategy compared to the conventional IVF/ICSI strategy (OR 0.26, 95% CI 0.17 to 0.39; I2 = 0%; 6 RCTs, 4478 women; low-quality evidence). These data suggest that for an OHSS rate of 3% following the conventional strategy, the rate following the 'freeze all' strategy would be 1%. There is probably little or no difference between the two strategies in the cumulative ongoing pregnancy rate (OR 0.95, 95% CI 0.75 to 1.19; I2 = 31%; 4 RCTs, 1245 women; moderate-quality evidence).  We could not analyse time to pregnancy; by design, time to pregnancy is shorter in the conventional strategy than in the 'freeze all' strategy when the cumulative live birth rate is comparable, as embryo transfer is delayed in a 'freeze all' strategy. We are uncertain whether the two strategies differ in cumulative miscarriage rate because the evidence is very low quality (Peto OR 1.06, 95% CI 0.72 to 1.55; I2 = 55%; 2 RCTs, 986 women; very low-quality evidence) and cumulative multiple-pregnancy rate (Peto OR 0.88, 95% CI 0.61 to 1.25; I2 = 63%; 2 RCTs, 986 women; very low-quality evidence). The risk of hypertensive disorders of pregnancy (Peto OR 2.15, 95% CI 1.42 to 3.25; I2 = 29%; 3 RCTs, 3940 women; low-quality evidence), having a large-for-gestational-age baby (Peto OR 1.96, 95% CI 1.51 to 2.55; I2 = 0%; 3 RCTs, 3940 women; low-quality evidence) and a higher birth weight of the children born (mean difference (MD) 127 g, 95% CI 77.1 to 177.8; I2 = 0%; 5 RCTs, 1607 singletons; moderate-quality evidence) may be increased following the 'freeze all' strategy. We are uncertain whether the two strategies differ in the risk of having a small-for-gestational-age baby because the evidence is low quality (Peto OR 0.82, 95% CI 0.65 to 1.05; I2 = 64%; 3 RCTs, 3940 women; low-quality evidence).

AUTHORS' CONCLUSIONS

We found moderate-quality evidence showing that one strategy is probably not superior to the other in terms of cumulative live birth rate and ongoing pregnancy rate. The risk of OHSS may be decreased in the 'freeze all' strategy. Based on the results of the included studies, we could not analyse time to pregnancy. It is likely to be shorter using a conventional IVF/ICSI strategy with fresh embryo transfer in the case of similar cumulative live birth rate, as embryo transfer is delayed in a 'freeze all' strategy. The risk of maternal hypertensive disorders of pregnancy, of having a large-for-gestational-age baby and a higher birth weight of the children born may be increased following the 'freeze all' strategy. We are uncertain if 'freeze all' strategy reduces the risk of miscarriage, multiple pregnancy rate or having a small-for-gestational-age baby compared to conventional IVF/ICSI.

Improving the clinical outcomes by extended culture of day 3 embryos with low blastomere number to blastocyst stage following frozen-thawed embryo transfer

Purpose

This study aimed to investigate whether the extended culture of day 3 (D3) embryos with low blastomere number to blastocyst following frozen–thawed embryo transfer improved the clinical outcomes.

Methods

This was a retrospective study of clinical data of women undergoing in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) cycles in the Tangdu Hospital. The patients were divided into groups with 4–5, 6, 7–9 and > 9 cells based on the blastomere number of D3 embryos. The clinical outcomes were compared.

Results

In fresh transfer cycles, the implantation and clinical pregnancy rates significantly decreased, while the abortion rate significantly increased in the groups with 4–5 and 6 cells compared with those with 7–9 and > 9 cells. In frozen–thawed transfer cycles, the clinical pregnancy and implantation rates for a single blastocyst transfer cycle showed no significant differences in the groups with 4–5 and 6 cells compared with those with 7–9 and > 9 cells. However, the abortion rate was significantly higher in the group with 4–5 cells than in that with 7–9 and > 9 cells. In the double blastocyst transfer cycle, the clinical pregnancy rate showed no significant differences among the groups with 4–5, 6, and 7–9 cells.

Conclusion

The implantation and clinical pregnancy rates of D3 embryos with 6 cells significantly decreased; these embryos were not considered as high-quality embryos. Extended culture of D3 embryos with ≤ 6 blastomeres to blastocysts, particularly 6-cell embryos, resulted in a similar clinical pregnancy rate as that of blastocysts derived from D3 embryos with ≥ 7 blastomeres.

Higher probability of live-birth in high, but not normal, responders after first frozen-embryo transfer in a freeze-only cycle strategy compared to fresh-embryo transfer: a meta-analysis

STUDY QUESTION

Does the outcome of the comparison of live birth rates between the first frozen embryo transfer (ET) (in a freeze-only cycles strategy, i.e. frozen ET group) and a fresh embryo transfer (fresh ET group) differ considering the type of ovarian response?

SUMMARY ANSWER

Α significantly higher probability of live birth is present in high, but not normal, responders, after the first frozen ET in a freeze-only cycle strategy as compared to a fresh ET.

WHAT IS KNOWN ALREADY

It has been hypothesised that freezing all good embryos in a fresh in-vitro fertilisation (IVF) cycle and deferring embryo transfer in subsequent cycles may provide a more physiological endometrial environment for embryo implantation when compared to a fresh ET. However, currently, three relevant meta-analyses have been published with conflicting results, while none of them has taken into consideration the type of ovarian response. Recently, the publication of additional, large relevant randomised controlled trials (RCTs) in patients with different types of ovarian response makes possible the comparative evaluation of the first frozen ET (in a freeze-only cycle strategy) versus fresh ET, considering the type of ovarian response.

STUDY DESIGN, SIZE, DURATION

A systematic review and meta-analysis was performed aiming to identify RCTs comparing the first frozen ET (in a freeze-only cycle strategy) to a fresh ET. The main outcome was live birth, while secondary outcomes included ongoing pregnancy, clinical pregnancy, moderate/severe ovarian hyperstimulation syndrome (OHSS) and miscarriage.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We identified eight eligible RCTs, including 5265 patients, which evaluated the first frozen ET in a freeze-only cycle strategy versus a fresh ET either in high responders (n = 4) or in normal responders (n = 4). No relevant RCTs were present in poor responders. Meta-analysis of weighted data using fixed and random effects model was performed. Results are reported as relative risk (RR) with 95% confidence interval (CI).

MAIN RESULTS AND THE ROLE OF CHANCE

Eligible RCTs were published between 2011 and 2018. Four RCTs (n = 3255 patients) compared the first frozen ET (in a freeze-only cycle strategy) to a fresh ET in normal responders and four RCTs (n = 2010 patients) did the comparison in high responders. In high responders, a significantly higher probability of live birth was observed in the frozen ET group when compared with the fresh ET group (RR: 1.18, 95% CI: 1.06-1.31; fixed effects model; heterogeneity: I2 = 0%; three studies; n = 3398 patients). However the probability of live birth was not significantly different between the frozen ET group and the fresh ET group in normal responders (RR: 1.13, 95% CI: 0.90-1.41; random effects model; heterogeneity: I2 = 77%; three studies; n = 1608 patients). The risk of moderate/severe OHSS was significantly lower in the frozen ET group when compared with the fresh ET group both in high (RR: 0.19, 95% CI: 0.10-0.37; fixed effects model; heterogeneity: not applicable; a single study; n = 1508 patients) and normal responders (RR: 0.39, 95% CI: 0.19-0.80; fixed effects model; heterogeneity: I2 = 0%; two studies; n = 2939 patients).

LIMITATIONS, REASONS FOR CAUTION

Considerable heterogeneity was present among the studies, regarding ovarian stimulation protocols and the triggering signal used for inducing final oocyte maturation as well as the cryopreservation methods, while the quality of evidence was poor for the live birth rate in high responders. Moreover, the analysis did not apply a standard for determining 'high' or 'normal' responders since the type of ovarian response followed the characterisation of populations as reported by the authors of the eligible studies.

WIDER IMPLICATIONS OF THE FINDINGS

A freeze-only cycle strategy should be the preferred option in high responders since it enhances the probability of live birth, while reducing the chance of moderate/severe OHSS. In normal responders, the same strategy could be applied, in the interest of patient safety or clinic convenience, without compromising the chances of live birth.

STUDY FUNDING/COMPETING INTEREST(S)

No external funding was used and there were no competing interests.

PROSPERO REGISTRATION NUMBER

PROSPERO registration number: CRD42018099389.

Fresh versus frozen embryo transfers in assisted reproduction

BACKGROUND

In general, in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI) implies a single fresh and one or more frozen-thawed embryo transfers. Alternatively, the 'freeze-all' strategy implies transfer of frozen-thawed embryos only, with no fresh embryo transfers. In practice, both strategies can vary technically including differences in freezing techniques and timing of transfer of cryopreservation, that is vitrification versus slow freezing, freezing of two pro-nucleate (2pn) versus cleavage-stage embryos versus blastocysts, and transfer of cleavage-stage embryos versus blastocysts.In the freeze-all strategy, embryo transfers are disengaged from ovarian stimulation in the initial treatment cycle. This could avoid a negative effect of ovarian hyperstimulation on the endometrium and thereby improve embryo implantation. It could also reduce the risk of ovarian hyperstimulation syndrome (OHSS) in the ovarian stimulation cycle by avoiding a pregnancy.We compared the benefits and risks of the two treatment strategies.

OBJECTIVES

To evaluate the effectiveness and safety of the freeze-all strategy compared to the conventional IVF/ICSI strategy in women undergoing assisted reproductive technology.

SEARCH METHODS

We searched the Cochrane Gynaecology and Fertility Group Trials Register, the Cochrane Central Register of Studies (CRSO), MEDLINE, Embase, PsycINFO, CINAHL, and two registers of ongoing trials in November 2016 together with reference checking and contact with study authors and experts in the field to identify additional studies.

SELECTION CRITERIA

We included randomised clinical trials comparing a freeze-all strategy with a conventional IVF/ICSI strategy which includes fresh transfer of embryos in women undergoing IVF or ICSI treatment.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures recommended by Cochrane. The primary review outcomes were cumulative live birth and OHSS. Secondary outcomes included other adverse effects (miscarriage rate).

MAIN RESULTS

We included four randomised clinical trials analysing a total of 1892 women comparing a freeze-all strategy with a conventional IVF/ICSI strategy. The evidence was of moderate to low quality due to serious risk of bias and (for some outcomes) serious imprecision. Risk of bias was associated with unclear blinding of investigators for preliminary outcomes of the study, unit of analysis error, and absence of adequate study termination rules.There was no clear evidence of a difference in cumulative live birth rate between the freeze-all strategy and the conventional IVF/ICSI strategy (odds ratio (OR) 1.09, 95% confidence interval (CI) 0.91 to 1.31; 4 trials; 1892 women; I² = 0%; moderate-quality evidence). This suggests that if the cumulative live birth rate is 58% following a conventional IVF/ICSI strategy, the rate following a freeze-all strategy would be between 56% and 65%.The prevalence of OHSS was lower after the freeze-all strategy compared to the conventional IVF/ICSI strategy (OR 0.24, 95% CI 0.15 to 0.38; 2 trials; 1633 women; I² = 0%; low-quality evidence). This suggests that if the OHSS rate is 7% following a conventional IVF/ICSI strategy, the rate following a freeze-all strategy would be between 1% and 3%.The freeze-all strategy was associated with fewer miscarriages (OR 0.67, 95% CI 0.52 to 0.86; 4 trials; 1892 women; I² = 0%; low-quality evidence) and a higher rate of pregnancy complications (OR 1.44, 95% CI 1.08 to 1.92; 2 trials; 1633 women; low-quality evidence). There was no difference in multiple pregnancies per woman after the first transfer (OR 1.11, 95% CI 0.85 to 1.44; 2 trials; 1630 women; low-quality evidence), and no data were reported for time to pregnancy.

AUTHORS' CONCLUSIONS

We found moderate-quality evidence showing that one strategy is not superior to the other in terms of cumulative live birth rates. Time to pregnancy was not reported, but it can be assumed to be shorter using a conventional IVF/ICSI strategy in the case of similar cumulative live birth rates, as embryo transfer is delayed in a freeze-all strategy. Low-quality evidence suggests that not performing a fresh transfer lowers the OHSS risk for women at risk of OHSS.