P–626 A freeze-all strategy improves clinical pregnancy rate in patients with few available embryos

Study question

Is elective frozen blastocyst transfer an advantageous strategy for all patients?

Summary answer

A freeze-all strategy improves the outcomes in patients with few available embryos.

What is known already

With the aim of defining the best moment to perform embryo transfer, in recent years, relevance has been given to the understanding of the implantation window, however oocyte and embryo quality are key factors that are not to be disregarded.

It has been suggested that a freeze-all strategy and subsequent frozen embryo transfers improve pregnancy rates. However, it is unclear whether this strategy benefits all kind of patients (i.e. with or without surplus embryos, etc).

In this study, we aim to provide an answer on which patients may benefit of a freeze-all policy and a subsequent frozen embryo transfer.

Study design, size, duration

This retrospective cohort study includes infertile patients aged 21 to 44 years old, without previous history of recurrent failure of ART (including recurrent miscarriages). Enrolments took place between January 2015 and November 2019 and cycles with oocyte donation and PGT were excluded. Embryo transfers were performed in: 1) a fresh cycle (ET) or 2) a deferred cycle with surplus frozen embryos (FET) or embryos that were frozen in a freeze-all policy (FET-FA).

Participants/materials, setting, methods

Patients with blastocysts transfer were included. PGT cycles were excluded.

The number of cycles complying with the inclusion criteria were: 617 ICSI cycles. Fresh embryo transfers (ET) were performed in 396 cycles (43 with a subsequent Frozen embryo transfer, FET). Frozen embryo transfers following a freeze-all strategy (FET-FA) were performed in 221 cycles.

Clinical pregnancy rates (CPR) and Cumulative clinical pregnancy rates (CCPR) were calculated and compared among those groups.

Main results and the role of chance

Mean age of patients was 36.1 ± 3.7 years old (mean ± SD). In average, 1.83 ± 0.41 (mean ± SD) embryos were transferred.

Following the first transfer (either ET and FET-FA), CPR was 40.4% and 58.4% (ET and FET-FA, respectively). Following the subset analysis of 2 age groups (≤38 & >38 years-old); in the ≤38-group, CPR was 45.2% and 58.9% (ET and FET-FA, respectively), while in > 38-group, the rates were 30.8% and 54.8% (ET and FET-FA, respectively); p < 0.05. CCPR were also significantly better in the FET-FA group: 51.3% vs 66.8% and 33.8% vs 58.1% in the ≤38-group and >38-group, respectively.

Additionally, CPR was analysed independently for patients with ≤2 usable embryos (1 attempt) or ≥ 3 usable embryos (surplus embryos after first attempt).

When a single attempt was possible; in the ≤38-group, CPR was 36.1% and 56.9% (ET and FET-FA, respectively) while in the >38-group, the rates were 24.7% and 63.6% (ET and FET-FA, respectively); p < 0.05. When surplus embryos were available, no difference in CPR (or CCPR) between ET and FET-FA groups were observed. After first attempt CPR were 58.4% and 48.2% in the ≤38-group & >38-group, respectively; while CCPR were 69.8% and 57.1% in the ≤38-group & >38-group, respectively.

Limitations, reasons for caution

Although the authors consider that the patient population is of optimal size, a detailed analysis of the stimulation protocol and hormonal values (estradiol and progesterone) during treatment, and its potential relation to the outcomes, should follow.

Wider implications of the findings: In our setting, the data suggests that freeze-all strategy (with subsequent frozen embryo transfer) over fresh transfer is advantageous for patients with few available embryos (1 or 2 embryos for a single attempt). This increases the chances to pregnancy in 30.3% in the ≤38-group and 77.9% in the >38-group.

Trial registration number

Not applicable

Deficient expression of monoamine oxidase A in the endometrium is associated with implantation failure in women participating as recipients in oocyte donation

Successful implantation depends both on the quality of the embryo and on the endometrial receptivity. The latter depends on progesterone-induced changes in gene expression, a process that has been characterized by microarray analysis. One of the genes whose transcription appears to be enhanced during the receptive period is monoamine oxidase A (MAO-A). Our first objective was to confirm the increased expression of MAO-A in the endometrium during the receptive phase of spontaneous normal cycles using real time PCR and immunofluorescence. The second objective was to examine the endometrial expression of MAO-A during the receptive phase induced by exogenous estradiol (E(2)) and progesterone in patients whose endometrium was shown to have been either receptive or non-receptive to embryo implantation in repeated cycles of oocyte donation. Results showed that MAO-A transcript levels increased between the pre-receptive (LH+3) and receptive phase (LH+7) in all spontaneous cycles examined, with a median increase of 25-fold. Immunofluorescent labelling demonstrated MAO-A localization to the glandular and luminal epithelium with an increasing positive score between LH+3 and LH+7. Conversely, prior failure of embryo implantation was associated with a 29-fold decrease in MAO-A mRNA levels and a substantial reduction in MAO-A protein immunofluorescent label score. These results show a strong association between endometrial receptivity and MAO-A expression in the endometrial epithelium, suggesting an important role for this enzyme in normal implantation.

Differential effects of polysulphates between mouse and hamster during in vitro fertilization

The interaction between zona pellucida polysulphates and sperm receptors appears to be a widespread mechanism used by mammals during gamete interaction. In this work, the effect of heparin on binding, penetration and fertilization of mouse and hamster oocytes was assessed. We found that heparin inhibited oocyte penetration and fertilization in both species. Heparin as well as fucoidan (a fucose-sulphate polymer) inhibited the proteolytic activity of acrosomal enzymes in both species. Our results suggest that zona pellucida penetration in both species may be modulated by polysulphates acting on either the proteolytic rate of degradation of the zona and/or its interaction with acrosome-reacted sperm (secondary binding).

Predictive value of human chorionic gonadotrophin in the outcome of early pregnancy after in-vitro fertilization and spontaneous conception

This prospective study analyses the value of the beta-subunit of human chorionic gonadotrophin (beta-HCG) in 120 pregnancies obtained after in-vitro fertilization (IVF)--embryo transfer. Spontaneous conception cycles (n = 16) were also analysed allowing a comparison between these two forms of conception. Of the 120 clinical pregnancies, 48 started as single gestations and 50 started with two or more sacs. There were 14 clinical abortions and eight ectopic pregnancies. All subjects had blood samples taken under a fixed protocol on days 11, 14, 17, 20 and 23 after follicular aspiration. Weekly samples were obtained thereafter until day 60 from ovum retrieval. Transvaginal ultrasounds were performed at weekly intervals, starting on day 23 after follicular aspiration. In spontaneous conception cycles blood samples were obtained daily, starting on the day of follicular rupture. In spontaneous conception cycles and in IVF-embryo transfer conceptions, the doubling time (DT) of beta-HCG was 1.4 +/- 0.3 and 1.6 +/- 0.4 days respectively. This difference was not significant. In multigestations, the DT was 1.5 +/- 0.3 days. The absolute values of beta-HCG in early spontaneous gestations were significantly higher than in IVF-embryo transfer cycles, suggesting that the blastocyst implants with less cellular mass when initiated in vitro as compared with the in-vivo condition. The early prediction of ectopic pregnancy and spontaneous clinical abortion was analysed by the beta-HCG profile as well as the absolute values in comparison to normal pregnancies. Both parameters showed significant differences as early as the interval between days 11 and 23 from follicular aspiration.(ABSTRACT TRUNCATED AT 250 WORDS)