A freeze-all strategy does not increase live birth rates in women of advanced reproductive age

Clinical outcomes after fresh versus frozen embryo transfer in women with advanced reproductive age undergoing in vitro fertilization: a propensity score-matched cohort study

This retrospective cohort study aimed to compare clinical outcomes following fresh or frozen embryo transfer (FET) in women with advanced reproductive age (ARA). Women aged 35-45 years who underwent their first autologous fresh or frozen cleavage stage embryo transfer cycle in the Centre for Assisted Reproduction of Shanghai First Maternity and Infant Hospital between January 2016 and December 2020 were included. The primary outcome was live birth after the first embryo transfer of the in vitro fertilization (IVF) cycle. Multiple covariates were used for propensity score matching (PSM) and generalized estimating equations were performed to examine the independent association between FET and live birth. Of the total 1453 patients, 327 patients had FET and 1126 patients had fresh ET. After the PSM procedure, 274 patients were included in each group. The live birth rate was 24.8% in the FET group and 25.2% in the fresh ET group (OR 0.98, 95% CI: 0.67-1.44, P = 0.92). Other pregnancy, perinatal and neonatal outcomes were all comparable between the two groups. This study showed that FET did not improve live birth and other clinical outcomes as compared with fresh embryo transfer in women with ARA who underwent their first IVF cycle.

The utility of all-freeze IVF cycles depends on the composition of study populations

BACKGROUND

Because often introduced without proper validation studies, so-called "add-ons" to IVF have adversely affected in vitro fertilization (IVF) outcomes worldwide. All-freeze cycles (embryo banking, EB) with subsequently deferred thaw cycles are such an "add-on" and, because of greatly diverging reported outcomes, have become increasingly controversial. Based on "modeling" with selected patient populations, we in this study investigated whether reported outcome discrepancies may be the consequence of biased patient selection.

RESULTS

In four distinct retrospective case control studies, we modeled in four cohort pairings how cryopreservation with subsequent thaw cycles affects outcomes differently in good-, average- and poor-prognosis patients: (i) 127 fresh vs. 193 frozen donor-recipient cycles to model best-prognosis patients; (ii) 741 autologous fresh non-donor IVF cycles vs. 217 autologous frozen non-donor IVF cycles to model average prognosis patients; (iii) 143 favorably selected autologous non-donor IVF cycles vs. the same 217 frozen autologous cycles non-donor to monitor good- vs. average-prognosis patients; and (iv) 598 average and poor-prognosis autologous non-donor cycles vs. the same 217 frozen autologous non-donor cycles to model poor vs. average prognosis patients. In best-prognosis patients, EB marginally improved IVF outcomes. In unselected patients, EB had no effects. In poor-prognosis patients, EB adversely affected IVF outcomes. Unexpectedly, the study also discovered independent-of-age-associated chromosomal abnormalities, a previously unreported effect of recipient age on miscarriage risk in donor-egg recipients.

CONCLUSIONS

In poor-prognosis patients, EB cycles should be considered contraindicated. In intermediate-prognosis patients EB does not appear to change outcomes, not warranting additional cost and time delays. Therefore, only good-prognosis patients are candidates for EB, though they will experience only marginal benefits that may not be cost-effective.

Fresh vs. frozen embryo transfer: new approach to minimize the limitations of using national surveillance data for clinical research

OBJECTIVE

To assess the benefit of frozen vs. fresh elective single embryo transfer using traditional and novel methods of controlling for confounding.

DESIGN

Retrospective cohort study using data from the National Assisted Reproductive Technology Surveillance System.

SETTING

Not applicable.

PATIENT(S)

A total of 44,750 women aged 20-35 years undergoing their first lifetime oocyte retrieval and embryo transfer in 2016-2017, who had ≥4 embryos cryopreserved.

INTERVENTION(S)

Fresh elective single embryo transfer and frozen elective single embryo transfer.

MAIN OUTCOME MEASURE(S)

The primary outcome was a singleton live birth. Secondary outcomes included rates of total live birth (singleton plus multiple gestations), twin live birth, clinical intrauterine gestation, total pregnancy loss, biochemical pregnancy, and ectopic pregnancy. Outcomes for infants included gestational age at delivery, birth weight, and being small for gestational age.

RESULT(S)

The eligibility criteria were met by 6,324 fresh and 2,318 frozen cycles. Patients undergoing fresh and frozen transfer had comparable mean age (30.69 [standard deviation {SD} 0.08] years vs. 31.06 [SD 0.08] years) and body mass index (24.76 [SD 0.20] vs. 25.65 [SD 0.15]); however, women in the frozen cohort created more embryos (8.1 [SD 0.12] vs. 6.8 [SD 0.08]). Singleton live birth rates in the fresh vs. frozen groups were 51.4% vs. 48.8% (risk ratio 1.05; 95% confidence interval [CI], 1.00-1.10). After adjustment with a log-linear regression model and propensity score analysis, the difference in singleton live birth rates remained nonsignificant (adjusted risk ratio, 1.05; 95% CI, 0.97-1.14 and 1.02; 95% CI, 0.96-1.08, respectively). A novel dynamical model confirmed inherent fertility (probability of ever achieving a pregnancy) was balanced between groups (odds ratio, 1.23; 95% CI 0.78-1.95]). The per-cycle probability of singleton live birth was not different between groups (odds ratio 1.11 [95% CI 0.94-1.3]).

CONCLUSION(S)

In this retrospective cohort study of fresh vs. frozen elective single embryo transfer, there was no statistically significant difference in singleton live birth rate after adjustment using log-linear models and propensity score analysis. The successful application of a novel dynamical model, which incorporates multiple assisted reproductive technology cycles from the same woman as a surrogate for inherent fertility, offers a novel and complementary perspective for assessing interventions using national surveillance data.

Is a freeze-all strategy necessary for all embryo transfers : Fresh embryo transfer without progesterone elevation results in an equivalent pregnancy rate to cryopreserved embryo transfer

Objectives : It has been suggested that the clinical outcomes of frozen-thawed embryo transfer (ET) are superior to those of fresh embryo transfer. We examined whether a freeze-all strategy is necessary for all embryo transfers, and, if not, to evaluate the conditions in which the pregnancy rates of fresh embryo transfer and frozen-thawed ET did not differ. Methods : Patients who underwent blastocyst transfer at Tokushima University Hospital between 2008 and 2019 were enrolled. The clinical outcomes and clinical characteristics of 1,022 patients that underwent fresh embryo transfer and 1,728 patients that underwent frozen-thawed ET were examined retrospectively. We considered the factors that influenced the pregnancy outcomes of fresh embryo transfer. Results : The frozen-thawed ET group exhibited significantly higher pregnancy, live-birth, and miscarriage rates than the fresh embryo transfer group. In the fresh embryo transfer group, a high progesterone level on the day of the human chorionic gonadotropin (hCG) trigger and lower grade embryos were risk factors for a low pregnancy rate. However, in the cases in which the progesterone level was < 1.0 ng / mL the pregnancy rate was equal to that of frozen-thawed ET. Conclusions : A freeze-all strategy is not necessary for embryo transfers, but should be employed in cases involving pre-ovulatory progesterone elevation. J. Med. Invest. 69 : 224-229, August, 2022.

Prolonged Cryopreservation Negatively Affects Embryo Transfer Outcomes Following the Elective Freeze-All Strategy: A Multicenter Retrospective Study

BACKGROUND

With the development of embryo freezing and warming technology, frozen-thawed embryo transfer (FET) has been widely utilized. However, studies investigating the association between cryopreservation duration and FET outcomes are limited and controversial, and previous studies did not conduct stratification analyses based on demographic or clinical characteristics.

METHODS

This multicenter retrospective study included 17,826 women who underwent their first FET following the freeze-all strategy during the period from January 2014 to December 2018. Duration of cryopreservation was categorized into five groups: 3-8 weeks, 8-12 weeks, 12-26 weeks, 26-52 weeks, and >52 weeks. Modified Poisson regression and multivariate logistic regression were used to assess the association between cryostorage time of vitrified embryos and transfer outcomes. Moreover, further stratification analyses were performed according to variables with p <0.05 in multivariate models.

RESULTS

In this large multicenter study, we observed that storage duration was inversely associated with the possibility of pregnancy and live birth (p <0.001), but not with the risk of ectopic pregnancy and miscarriage. Stratification analyses based on maternal age, the number of oocytes retrieved, and condition of embryo transferred indicated that the inverse correlation was significant in the subpopulation with characteristics: (1) less than 40 years old, (2) more than 3 oocytes retrieved, and (3) only high-quality blastocysts transferred.

CONCLUSION

The results of this large, multicenter, retrospective study suggested that prolonged cryopreservation was inversely associated with the probability of pregnancy and live birth. Therefore, for patients who adopt a freeze-all strategy, early FET might achieve a better outcome.