The impact of a second embryo biopsy for preimplantation genetic testing for monogenic diseases (PGT-M) with inconclusive results on pregnancy potential: results from a matched case-control study

PURPOSE

To evaluate whether a second biopsy, following a first diagnostic failure on blastocysts tested for preimplantation genetic testing for monogenic diseases (PGT-M), allows to obtain genetic diagnosis and to what extent this procedure can influence clinical pregnancy and live birth rates compared to the PGT-M process with a successful genetic diagnosis from the first biopsy.

METHODS

Embryos from women who underwent PGT-M in an infertility centre and who had been transferred after two biopsies for genetic analysis (n = 27) were matched in a 1:1 ratio accordingly to women's age (± 1 year) and fertility status (fertile vs infertile), as well as with the study period, with embryos who were transferred after receiving a conclusive PGT result straight after the first biopsy (n = 27). The main evaluated outcome was clinical pregnancy rate following embryo transfers in which healthy embryos were transferred after only one biopsy and those in which an embryo was transferred after being re-biopsied. Live birth rate was the secondary outcome.

RESULTS

Clinical pregnancy rate was 52% (95% CI: 34-69) following the transfer of a single-biopsy blastocyst and 30% (95% CI: 16-48) following the transfer of a re-biopsied blastocyst. The likelihood to have a healthy baby was 33% (95% CI: 19-52) following the transfer of a blastocyst biopsied once and 22% (95% CI: 11-41) following the transfer of a re-biopsied blastocyst.

CONCLUSIONS

The re-biopsy intervention seems to considerably reduce the pregnancy potential of a blastocyst. However, a greater sample size is necessary to clarify this issue definitively.

Conventional in vitro fertilisation rather than intracytoplasmic sperm injection when only one oocyte is retrieved: Time to overcome irrational fears

BACKGROUND

The use of intracytoplasmic sperm injection (ICSI) currently extends beyond male factor infertility, notably replacing conventional in vitro fertilisation (IVF) in scenarios like limited oocyte availability, where it is used as a precaution against complete fertilisation failure. While existing studies on the use of conventional IVF in such situations provide some reassurance, the available evidence is somewhat insufficient and ICSI is commonly used.

AIMS

To evaluate whether conventional IVF can be a feasible option when only one oocyte is retrieved.

MATERIALS AND METHODS

A retrospective study was performed to evaluate the fertilisation rate with conventional IVF in women retrieving only one oocyte and whose partner had normal semen. The study aimed at evaluating whether the fertilisation rate was aligned with the threshold indicated by recognized IVF laboratory performance indicators (Vienna Consensus). Clinical pregnancy and live birth rates were secondary outcomes.

RESULTS

Out of 304 cycles with a single oocyte inseminated with conventional IVF, 209 achieved normal fertilisation and 82 did not. Thirteen had no mature oocytes. The fertilisation rate was 69% (95% CI: 63-74%) and increased to 72% (95% CI: 66-77%) when immature oocytes were excluded. The fertilisation rate surpassed the minimum competency threshold of the Vienna Consensus (60%), even if below the benchmark value (75%). Clinical pregnancy and live birth rates per oocyte retrieval were 10% and 8%, respectively. Univariate and multivariate analyses failed to identify any predictive factor of fertilisation.

CONCLUSION

Conventional IVF with one oocyte met Vienna Consensus standards even if it fell short of higher benchmarks.

Follicular steroidogenesis in random start protocols for oocyte cryopreservation

PURPOSE

Random start protocols are commonly used for oocyte cryopreservation in women with cancer. However, albeit generally reassuring, available evidence is still insufficient to rule out a sub-optimal cycle outcome. This study aimed to compare follicular steroidogenesis between women initiating the random start protocol in the luteal phase and those initiating in the follicular phase.

METHODS

Consecutive women with cancer scheduled for oocyte cryostorage were prospectively recruited. We excluded those requiring a concomitant letrozole assumption. All women received a standardized protocol with recombinant FSH and GnRH antagonists. At the time of oocyte retrieval, follicular fluids were pooled, and a sample was collected and frozen at -80 °C. All samples were assayed concomitantly after thawing by liquid chromatography-tandem mass spectrometry. The concentration of 15 different steroid hormones was determined.

RESULTS

Seventy-one women were recruited. Thirty-three initiated the ovarian stimulation in the luteal phase, while the remaining 38 initiated in the follicular phase. Baseline characteristics were generally similar. Cycle outcome did also not differ; the median (interquartile range) number of frozen mature oocytes was 9 (5-14) and 10 (5-21), respectively (p = 0.42). None of the 15 tested steroid hormones differed.

CONCLUSIONS

The endocrine microenvironment surrounding oocytes is not markedly influenced by the phase of the menstrual cycle at the initiation of ovarian stimulation. This result further supports the validity of random start protocols.

P-212 Impact of post-thaw blastocyst culture time prior to transfer on live birth rate in frozen-thawed embryo transfer cycles: a retrospective observational study

Study question

Does post-thaw blastocyst culture time prior to transfer influence the live birth rate in frozen-thawed embryo transfer cycles?

Summary answer

Our study revealed that different culture times of frozen-thawed blastocysts prior to transfer does not influence live birth rate.

What is known already

Several studies demonstrated a significantly increased clinical pregnancy rate after a frozen-thawed embryo transfer (FET) compared to a fresh embryo transfer (ET). FET reduces the risk of ovarian hyperstimulation syndrome without facing adverse effects of supraphysiological hormonal levels over endometrial receptivity. However, little is known on the effect of post-thaw embryo culture duration prior to transfer on live birth rate in FET cycles. Recent findings described an improved blastocyst morphological grade after a 20-22h post-thaw culture. Of note, the overnight culture of non-ideal morphology thawed blastocysts prior to transfer resulted in an enhanced live birth rate.

Study design, size, duration

We compared the live birth rate of patients undergoing FET after a short blastocyst culture time (2-4h) prior to transfer to that of patients in whom thawed blastocysts were transferred after a long embryo culture time (20-22h). Frozen-thawed transfers of blastocysts vitrified at Day 5 and subsequently thawed were evaluated. Only transfers of single blastocyst were included.

Participants/materials, setting, methods

The study was conducted at the Infertility Center – Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan. We included couples with indications for IVF cycles who underwent frozen-thawed blastocyst transfer procedure on the following natural cycles for freeze-all strategy or to transfer supernumerary embryos from 2014-2021. Data were analyzed using SPSS Statistics software. We evaluated statistically significant differences using various tests including Fisher's test, chi-squared test and Wilcoxon's test.

Main results and the role of chance

A total of 2012 frozen-thawed cycles were included in the analysis; in 977 of them, blastocysts were transferred after a 2-4h post-thaw period and in 1035, blastocysts were transferred after a 20-22h post thaw culture period. The age of the women was comparable (35.4 ± 4.2 and 35.3 ± 4.1; p = 0.5, respectively in the short and long culture period). According to statistical analysis, no significant difference in pregnancy outcomes was found between the two groups. Live birth rate was respectively 40% and 42% ( p = 0.2) in the short and long post-thaw blastocyst culture period prior to transfer.

Limitations, reasons for caution

Our study was limited by the retrospective nature and was performed in a single fertility center. Moreover, only blastocysts vitrified on day 5 were evaluated and findings might not be generalized to day 6 and 7 blastocysts.

Wider implications of the findings

These findings might be useful in the context of the organization of the laboratory workflow. Indeed, the possibility to thaw blastocysts on the day before transfer may represent an advantage in order to avoid an overload of the laboratory procedures during very busy days.

Trial registration number

28_2022