The Essential Guide to Understanding Embryo Grading
There are many reasons people turn to IVF, but the goal is always the same – they want to start or grow a healthy and happy family. Naturally, you’ll want to feel confident and safe that your clinic is doing everything possible to help you along your journey. One step in that process is embryo grading.
The evaluation process helps you and your team choose the most viable embryo for transfer. Embryos graded as top-quality embryos on day 5 or 6 have a significantly higher implantation rate, with success rates ranging from 40% to 60% per transfer.
Understanding embryo grading can initially seem confusing or daunting (after all, there’s a lot of scientific jargon), but we’ll break down all the essential info for you.
Jump to…
- What is embryo grading?
- When does embryo grading happen?
- How the traditional embryo grading process works
- How AIVF’s technology is transforming embryo scoring
- How embryo grading works: step by step
- The challenges in the current embryo grading system
- AIVF: Advanced embryo scoring for your IVF success
What is embryo grading?
Embryo grading is a scoring system used by embryologists to determine the quality of each embryo based on its morphological appearance (aka., its structure and development). Based on the grading results, embryologists and fertility doctors choose which embryos to use during the transfer process to maximize the chances of success. It’s essential to remember that embryo grading doesn’t predict or guarantee the final pregnancy outcome.
Although grading systems may differ across clinics, embryologists typically use an alphanumeric score (a score of letters and numbers, e.g., 5AA) and review factors like size and cell growth.
Embryo grading helps embryologists make informed, data-driven decisions on which embryo to select for transfer, helping reduce human bias and subjectivity.
For patients, it gives them more visibility into how embryos are selected and helps them stay in the loop to keep the nerves at bay. IVF is a complicated process that can be super stressful—the more insight and support you have along your journey, the better equipped you are to know what to expect and truly understand your options.
When does embryo grading happen?
The embryo grading process happens at the early stages of the IVF journey, after the egg collection and before the embryo transfer or freezing. After successful egg fertilization, the fertility specialists will monitor the embryo development.
The embryos can be graded on days 3 and 5 of this process—keep reading to find out how. After embryologists grade your embryos, you can either progress to the transfer or have the clinic freeze your embryos to complete the transfer in the future. You can also opt to transfer one and freeze the others.
How the traditional embryo grading process works
Embryologists currently assess embryo quality by combining visual evaluations with developmental milestones, usually conducted on day 3 and day 5 after fertilization. They closely monitor embryos under a microscope and analyze factors such as the number of cells and inner cell mass.
Some clinics also use time-lapse imaging (TLI) technology, which takes regular images of the embryos to monitor their development noninvasively. However, the process is still predominantly manual.
How AIVF’s technology is transforming embryo scoring
Thanks to AI technology for IVF, there have also been many exciting developments in the embryo scoring field. Innovative solutions like AIVF use deep learning algorithms to recognize complex patterns in time-lapse embryo images that are invisible to the human eye, including the embryologists who usually review the embryos via a microscope.
This computer vision reduces the subjectivity and variability of pre-defined embryo grading. For example, AIVF’s machine learning models can measure embryo shape, size, and structure, providing advanced analytics to help increase the transparency and success of your IVF journey.
How embryo grading works: step by step
Embryologists most commonly grade embryos at two different stages: day 3 and day 5. However, there are some instances in which the embryologist might grade the embryo past day 5 if there is late blastocyst development (your embryo has reached the blastocyst stage later than usual—we will explain this stage below).
In addition to the embryo grading completed on days 3 and 5, the clinic will consider other factors, like your age, health, and fertility history, before they proceed to implementation.
Here’s how the embryos are graded:
Day 3 (Cleavage stage)
Day 3 embryos are at the cleavage stage, which means they are dividing (“cleaving”) but not growing. These embryos still have an outer “shell” (the zona pellucida). We can use the birthday cake analogy to describe this stage: when you cut a birthday cake, you get more pieces, but the cake doesn’t get bigger (unfortunately!).
Clinics will likely grade day 3 embryos based on the following:
- Rate of growth: Whether the embryo is growing as expected based on the number of cells. At this point, the embryo should have divided two or three times into six to 10 cells.
- Degree of fragmentation: Fragments in the cytoplasm (the liquid that fills the inside of the cell) can indicate a lower-quality embryo.
- Evenness of cells: The symmetry of the cells. Ideally, the cells will be symmetrical.
Day 5 (Blastocyst stage)
Between day 3 and day 5, embryos develop a cell structure of fetal cells (which form an inner cell mass) and placental cells (also called trophectoderm or the outer cell mass). At the blastocyst stage, the embryo begins to fill with fluid and expand; then, it hatches out of the zona pellucida.
Now, embryologists will be able to see a different structure, and the grading is more complex based on the following:
- Degree of expansion: Size of the blastocyst cavity (a fluid-filled cavity) versus the embryo’s size. The bigger the cavity, the better the score is.
- Appearance of the inner cell mass: An evaluation of the quality of the inner cell mass based on how tightly packed the cells are. Tightly packed cells equal good quality.
- Appearance of the trophectoderm: How evenly distributed the cells are in the trophectoderm. The highest quality trophectoderm will have many cells of equal sizes in a well-formed layer.
The challenges in the current embryo grading system
Manual processes, prone to human bias
Embryo grading involves visually assessing and categorizing embryos based on their development under a microscope. It is a highly manual process that relies on the expertise and opinion of the individual embryologist,
There is no standardized embryo grading system, so the process varies between labs. This subjectivity creates a lack of consistency and standardization across clinics, opening the door to each embryologist’s biases and experiences. Ultimately, bias can disrupt the decision-making process at a critical moment when you need clarity.
Bottlenecks in communication
The lack of automated tools for embryo grading creates productivity bottlenecks and limits collaboration among team members. As a result, it takes longer for embryologists to grade embryos and reach decisions, which delays the entire IVF process.
By this point, patients have already undergone various physically demanding steps, from daily injections to frequent scans and egg retrieval. The cumulative effect of these delays adds to the physical and emotional toll on patients.
Limited predictive power
Current embryo grading systems can offer unexpected or flawed outcomes. For example, an embryo considered lower quality could result in a successful pregnancy, and vice versa. After investing time, money, and, most importantly, emotion into the IVF process, you want to know that the clinic has maximized your chance of success, especially at the early embryo implantation stage.
Technological limitations
Traditional embryo grading is limited to humans and a microscope, but technological advancements are helping patients have smoother, faster, and more successful IVF journeys. AI has the potential to provide standardized and highly reliable embryo grading at a level of scale and reliability that is impossible for embryologists.
Research by the Journal of Assisted Reproduction and Genetics found that clinics using sophisticated grading techniques, including AI-assisted systems, report up to a 30% increase in live birth rates per IVF cycle compared to those using only conventional grading. Other reports confirm that AI-based grading systems have been associated with a 15-25% increase in overall IVF success rates, reflecting better embryo selection and reduced cycles needed for achieving pregnancy.
AIVF: Advanced embryo scoring for your IVF success
Understanding how your embryos are graded is essential for assessing your IVF journey’s progress and potential outcome.
AIVF enables a new era of embryo scoring and visibility for patients, combining technology with compassionate care. Our solution leverages AI and ML and the world’s largest database of embryo images to assess your embryos and score them across various parameters, such as morphology, development stage, and other viability indicators.
Our scoring system ranks each embryo with a score between 1 and 99 (which correlates with the embryo’s ascending quality and likelihood of pregnancy success). This solution helps your clinic choose the best possible embryo for transfer and improves your chances of pregnancy success.
Equally important, it makes embryo grading and selection clear and intuitive for everyone so you can enjoy a greater understanding and clarity at each stage of your IVF process.
Find an AIVF clinic to get started on a transparent IVF journey unique to you.