Embryo evaluation: understanding embryo quality assessment

1. The role of embryo and PGT-A quality assessment in 2026
2. Success rates and the relationship of morphology to genetics
3. Features of embryo quality assessment in the UK and international standards
4. Transfer success rates: from good quality embryo to pregnancy. Average implant rate up to 70%
5. Criteria for morphological evaluation of embryos on different days of development
6. Evaluation of embryos at the fragmentation stage (day 2-3)
7. Assessment of embryo quality at the blastocyst stage (Day 5-7)
8. Gardner embryo evaluation table (Day 5)
9. Why is morphology not equal to genetics?
10. First number: degree of expansion of the blastocyst
11. First letter: inner cell mass quality (ICM)
12. Second letter: trophectoderm (TE) quality

This genetic analysis is complemented by a morphological evaluation of the embryos (evaluation by appearance): at the cleavage stage, embryos are classified from Grade 1 (excellent) with 7-10 cells and fragmentation less than 10% (high implantation potential) to grade 2 (good) with 6-8 cells and fragmentation of 10-25%. Grade 3 and 4 embryos are characterized by fragmentation of more than 25-50% and pronounced asymmetry of blastomeres, which indicates a low potential for gestation.

Bilateral embryo evaluation is a critical step in the surrogacy programs in Europe and oocyte donation programs from the Feskov Human Reproduction Group. The Feskov Human Reproduction Group clinic also carries out detailed classification (including the Gardner system for blastocysts, e.g. 5AA), which allows to achieve an implantation probability of up to 70%, guaranteeing the birth of a healthy child in IVF and surrogacy programs.

Feskov Human Reproduction Group is the best reproductive clinic that guarantees an unlimited number of IVF and the birth of a healthy child of the desired sex under a fixed-price contract.

We will tell you how we evaluate embryos to guarantee you the birth of a healthy child.

The role of embryo and PGT-A quality assessment in 2026

Morphological assessment of embryo quality is the first and most important step that allows embryologists to predict implantation success rates. However, as practice shows in 2026, only visual analysis of embryo evaluation cannot guarantee normal chromosome al set.

Therefore, modern protocols of leading clinics, including Feskov Human Reproduction Group, integrate morphological evaluation of embryos with PGT-A (preimplantation genetic testing for aneuploidy) and PGT-M (preimplantation genetic testing for monogenic diseases).

PGT-A is a test that determines whether an embryo is euploid (has a normal number of chromosomes – 46) or aneuploid (has an excess or insufficient number of chromosomes, <46 or >46):

1. Morphological assessment: analysis of external structure and development.
2. Genetic assessment (PGT-A/PGT-M): chromosomal health analysis.

Embryo quality assessment is a multifaceted process aimed at selecting the embryo with the highest potential for implantation in the uterine cavity.

Criteria for morphological evaluation of embryos on different days of development

The process of evaluating embryos differs depending on the day of cultivation. The embryologist monitors how quickly the cells divide, how symmetrical they are, and what percentage of fragmentation is present. Differences in criteria for the cleavage stages (day 2-3) and the blastocyst stage (day 5-7) are critical to the formation of an objective assessment of embryo quality.

Evaluation of embryos at the fragmentation stage (day 2-3)

On the 2nd-3rd day of development, the embryo is in the stage of cleavage, when the cells (blastomeres) are actively dividing. Embryo quality assessment at this stage focuses on three main indicators:

1. Number of cells (blastomeres): 4 cells are expected on the 2nd day, 6 to 8 cells on the 3rd day. Too fast or too slow division may indicate a poor quality embryo.
2. Blastomere symmetry: Ideal cells should be about the same size. Strong asymmetry reduces success rates.
3. Fragmentation: This is the appearance of small non-nucleated cell regions. The lower the percentage of fragmentation, the higher the quality of the embryo.

Below is a summary table of embryo evaluation at the cleavage stage:

The early stage embryo evaluation table helps the embryologist make a preliminary decision to extend the cultivation to the blastocyst stage in order to obtain a more accurate assessment of the quality of the embryos.

Assessment of embryo quality at the blastocyst stage (Day 5-7)

The blastocyst stage is preferred for transfer and biopsy (for PGT-A), as the embryo shows its potential best at this stage. Embryos are evaluated at the blastocyst stage according to an international standard known as the Gardner scoring system.

According to this system, the embryo quality assessment consists of three elements: a number and two letters (e.g., 5AA, 3BC).

First number: degree of expansion of the blastocyst

This number reflects the degree of expansion of the embryo and its readiness to "hatch" (hatching). The higher the number, the more developed the blastocyst, which is a good indicator of success.

1. Early blastocyst: a cavity less than half the volume of the embryo.
2. Blastocyst: a cavity of more than half the volume of the embryo.
3. Complete blastocyst: the cavity completely filled the embryo.
4. Enlarged blastocyst: the cavity is larger than the original volume of the embryo, the membrane is thin.
5. Hatching begins: the blastocyst began to emerge from the shell.
6. Mature blastocyst: the embryo has completely left the membrane.

Degrees of expansion 3, 4, 5, and 6 are generally considered optimal for cryopreservation and transfer.

First letter: inner cell mass quality (ICM)

The ICM is the part of the embryo that forms the fetus. Its quality is critical for implantation success rates.

Second letter: trophectoderm (TE) quality

Trophectoderm is the outer layer of cells that forms the placenta. Its quality affects the ability of the embryo to implant in the uterine wall.

Based on these three criteria, embryologists assign a final assessment of the quality of embryos.

Gardner embryo evaluation table (Day 5)

This embryo quality table demonstrates how criteria are combined to determine overall potential.

The Gardner embryo evaluation table is a unified tool that allows embryologists around the world, including clinics in the UK and the EU, to uniquely classify embryo quality and predict pregnancy success rates.

Success rates and the relationship of morphology to genetics

It is important to understand that the morphological evaluation of embryos only reflects how well the embryo has developed. A high score (e.g., 5AA) indicates that the embryo has developed well, but does not report its chromosomal health.

Why is morphology not equal to genetics?

Numerous studies have shown that the percentage of euploidy (genetic health) decreases with the age of the mother, regardless of external evaluation of embryo quality.

Here are the main reasons why assessing the quality of embryos requires genetic confirmation:

1. Age factor: A woman in her 40s may have a 5AA embryo, but there is a 60-80% chance that it will be aneuploid.
2. Hidden defects: even an embryo of good external quality can contain structural chromosomal abnormalities (deletions, translocations) that can only be detected with the help of PGT-A.
3. Mosaicism: In some cases, a blastocyst can contain both normal and abnormal cells. PGT-A allows you to detect this mosaicism, which may be associated with lower success rates.

Feskov Human Reproduction Group recommends transfer only embryos of good quality: morphologically strong and genetically euploid. If a woman of older reproductive age plans to carry a child herself without resorting to the services of a surrogate mother, stem cell treatment during IVF can increase the chances of successful pregnancy. The combination of a high-quality embryo and a good condition of the uterine endometrium gives a good chance of a successful pregnancy.

Features of embryo quality assessment in the UK and international standards

The practice of assessing the quality of embryos in the UK (according to HFEA) and in other European countries and the USA is generally in line with the international consensus, using the Gardner system (in the UK its equivalent developed by the Association of Clinical Embryologists of Great Britain – ACE). This standard allows for uniformity and a high level of success rates.

The process of assessing the quality of embryos in an international clinic includes the following stages:

1. Long-term cultivation: Embryos are evaluated up to the blastocyst stage (day 5-7) for natural selection of the most viable.
2. Use of time-lapse systems: Modern incubators, such as EmbryoScope, allow continuous assessment of embryo quality without removing them from the incubator. This provides more objective information about the rate and time of division and helps to identify early abnormalities that indicate a poor quality embryo.
3. Biopsy for PGT-A: If the quality of the embryo is high (e.g., 4AA and above), the embryologist performs a biopsy of several trophectoderm cells.
4. Vitrification: Embryos that have undergone a biopsy are cryopreserved (vitrified) until a genetic result is obtained. The quality of the embryo (especially TE) directly affects survival after thawing.

The combination of these technologies allows Feskov Human Reproduction Group to achieve high efficiency of embryo transfers and guarantee the birth of a healthy child to future parents.

Transfer success rates: from good quality embryo to pregnancy. Average implant rate up to 70%

The ultimate goal of embryo evaluation is to maximize success rates and reduce the risk of multiple pregnancies through the transfer of the best embryo (eSET – elective Single Embryo Transfer).

• good quality embryo (euploid, 5AA/5AB): has a chance of implantation up to 60-70%.
• poor quality embryo (aneuploid, 3CC): has a close to zero chance of implantation.

A thorough and multi-level assessment of the quality of embryos in Feskov Human Reproduction Group allows you to achieve an average implantation rate of 70% for the successful birth of a healthy child and the fulfillment of obligations to surrogate mothers and future parents. Get a free individual legal roadmap for the birth of your child – contact the manager on the website!