Which embryo selection method should be offered to the patients?

Current and future methods for embryo selection: on a quest for reliable strategies to reduce time to pregnancy

INTRODUCTION

The aim of this study was to analyze the usefulness of the principal embryological strategies to reduce time to pregnancy.

EVIDENCE ACQUISITION

A systematic search of publications in the PubMed/MEDLINE, Embase and Scopus databases from inception to present including "IVF," "blastocyst," "embryo colture," "competent embryo," "time to pregnancy," "aneuploid," "euploid," "vitrification," "preimplantation genetic," "IVF strategies" and "embryo selection" alone or in combinations has been done.

EVIDENCE SYNTHESIS

We have selected 230 articles and 9 of them have been included in this mini-review.

CONCLUSIONS

Several embryological strategies aimed to select the most competent embryo and reduce time to pregnancy have been proposed, even if few publications on this specific topic are available. preimplantation genetic testing (PGT-A) represents the unique method able to assess the embryonic chromosomal status, but this does not mean that PGT-A is a reliable strategy to reduce time to pregnancy. There is no consensus on a specific method to reduce time to pregnancy, nevertheless this final goal could be probably reached through a harmonious combination of procedures. Thus, a reliable strategy to reduce time to pregnancy could be achieved when embryo culture, embryo cryopreservation and PGT-A are perfectly integrated and appropriately offered to selected patients.

Non-invasive evaluation of embryos using mid-infrared attenuated total reflection spectrometry of incubation medium: a preliminary study

RESEARCH QUESTION

Can mid-infrared attenuated total reflection (MIR ATR) spectroscopy combined with machine learning methods be used as an additional tool to predict embryo quality and IVF treatment outcomes?

DESIGN

Spent culture media was collected and analysed. MIR ATR absorbance spectra were measured using an ALPHA II spectrometer equipped with an attenuated total reflection (ATR) spectrometry accessory. Patient and treatment data and results were collected and analysed in combination with machine learning techniques to identify possible correlations. The main outcome measures were to define the characteristics of absorbance spectra of spent culture media and to distinguish the difference in absorbance between top- and low-quality embryos, day 3 and day 5 embryos and implanting embryos versus non-implanting embryos.

RESULTS

Spent culture media of 227 embryos was collected and analysed. Absorbance peaks in the culture media were different between day 3 and day 5 embryos. Moreover, significant differences in P-values, spanning from 0.014 to 0.044 in absorbance peaks for day 3 embryos and 0.024 up to 0.04 for day 5 embryos, were seen between implanting and non-implanting embryos. Machine learning techniques offered a pregnancy prediction value of 84.6% for day 3 embryos.

CONCLUSIONS

MIR ATR may offer an additional parameter for better selection of embryos based on the spectrometric absorbance and secretions of metabolites in the culture media.

Focus on time-lapse analysis: blastocyst collapse and morphometric assessment as new features of embryo viability

The main goal of assisted reproductive technology (ART) is to achieve a healthy singleton live birth after the transfer of one embryo. A major objective of IVF scientists has always been to use adequate criteria for selecting the embryo for transfer according to its implantation potential. Indeed, embryo quality is usually assessed by evaluating visual morphology, which relies on the removal of the embryo from the incubator and might include inter- and intra-evaluator variation among embryologists. Recently, an advancement in embryo culture has taken place with the introduction of a new type of incubator with an integrated time-lapse monitoring system, which enables embryologists to analyse the dynamic events of embryo development from fertilization to blastocyst formation. This novel practice is rapidly growing and has been used in many IVF centres worldwide. Therefore, the main aim of this review is to present the benefits of time-lapse monitoring in a modern embryology laboratory; in particular, we discuss blastocyst collapse and morphometric blastocyst assessment, and analyse their association with embryo viability and implantation potential. In addition, we highlight preliminary studies involving artificial intelligence and machine learning models as non-invasive markers of clinical pregnancy.

The clinical use of time-lapse in human-assisted reproduction

A major challenge in the assisted reproduction laboratory is to set up reproducible and efficient criteria to identify the embryo with the highest developmental potential. Over the years, several methods have been used worldwide with this purpose. Initially, standard morphology assessment was the only available strategy. It is now universally recognized that besides being a very subjective embryo selection strategy, morphology evaluation alone has a very poor prognostic value. More recently, the availability of time-lapse incubators allowed a continuous monitoring of human embryo development. This technology has spread quickly and many fertility clinics over the world produced a remarkable amount of data. To date, however, a general consensus on which variables, or combination of variables, should play a central role in embryo selection is still lacking. Many confounding factors, concerning both patient features and clinical and biological procedures, have been observed to influence embryo development. In addition, several studies have reported unexpected positive outcomes, even in the presence of abnormal developmental criteria. While it does not seem that time-lapse technology is ready to entirely replace the more invasive preimplantation genetic testing in identifying the embryo with the highest implantation potential, it is certainly true that its application is rapidly growing, becoming progressively more accurate. Studies involving artificial intelligence and deep-learning models as well as combining morphokinetic with other non-invasive markers of embryo development, are currently ongoing, raising hopes for its successful applicability for clinical purpose in the near future. The present review mainly focuses on data published starting from the first decade of 2000, when time-lapse technology was introduced as a routine clinical practice in the infertility centers.

Embryo incubation by time-lapse systems versus conventional incubators in Chinese women with diminished ovarian reserve undergoing IVF/ICSI: a study protocol for a randomised controlled trial

INTRODUCTION

The time-lapse imaging system (TLS) is a newly developed non-invasive embryo assessment system. Compared with conventional incubators, a TLS provides stable culture conditions and consistent observations of embryo development, thereby potentially improving embryo quality and selection of the best quality embryo. Although TLSs have been routinely used in many in vitro fertilisation (IVF) centres globally, there is insufficient evidence to indicate that TLSs result in higher cumulative live birth rates over conventional incubators. The purpose of this study is to compare the cumulative live birth rates and safety including miscarriage in infertile patients with diminished ovarian reserve (DOR) from both TLSs and conventional incubators.

METHODS AND ANALYSIS

This study is a double-blind randomised controlled clinical trial (1:1 treatment ratio of TLSs vs conventional incubator). A total of 730 patients with DOR undergoing the first or second cycle of IVF or intracytoplasmic sperm injection (ICSI) will be enrolled and randomised into two parallel groups. Participants will undergo embryo culture in the TLSs (group A) or the conventional incubators (group B), respectively. Embryos are selected for transfer in both groups by the morphological characteristics. The embryo selection algorithm software is not used in the TLSs. The primary outcome is the cumulative live birth rate of the trial IVF/ICSI cycle within 12 months after randomisation. This study is powered to detect an absolute difference of 10% (35% vs 25%) at the significance level of 0.05% and 80% statistical power based on a two-sided test.

ETHICS AND DISSEMINATION

This trial has been approved by the Institutional Ethical Committee of Shanghai First Maternity and Infant Hospital (KS1958). All participants in the trial will provide written informed consent. The study will be conducted according to the principles outlined in the Declaration of Helsinki and its amendments. Results of this study will be disseminated in peer-reviewed scientific journals.

TRIAL REGISTRATION NUMBER

Chinese Clinical Trial Registry (ChiCTR1900027746).