Eeva test: a method to optimize embryo selection

The Eeva test, which stands for Early Embryo Viability Assessment (EVA), allows early prediction of which embryos have the greatest developmental potential.

In this way, a better selection of the embryo to be transferred to the maternal uterus can be made in order to improve the success rates of assisted reproduction treatments.

This is possible thanks to a time-lapse system attached to the incubator. It is a camera that takes serial images of the entire development of the embryo while it is inside the incubator. Time-lapse allows for continuous monitoring of embryos, but also to maintain much more stable conditions necessary for embryo development. This is because time-lapse avoids having to remove the embryo from the incubator to observe and evaluate it under the microscope as with traditional incubators.

The different sections of this article have been assembled into the following table of contents.

What is the Eeva test?

It is a tool that predicts the developmental potential of embryos, which is very useful when choosing the embryo to transfer in in vitro fertilization (IVF) cycles.

Eeva uses an algorithm that takes into account the time at which the first embryonic divisions occur, which Eeva is able to detect automatically (although embryologist supervision is recommended). In order to do this, Eeva relies on serial photographs of the embryo's first days of life obtained with a time-lapse system.

Thus, on day 3 of embryo development, Eeva is able to predict which embryos are most likely to give rise to a blastocyst. Thus, this system helps the embryologist to select which embryo will be the candidate to transfer to the patient.

The Eeva system can be incorporated into a traditional incubator to capture serial images for analysis. However, the Eeva test can now be performed directly in Geri+ incubators.

Eeva test incorporated in Geri+

If you want to know more about the Geri incubator, you can click here: What is the Geri and what advantages does it offer in assisted reproduction?

Traditional embryo selection

To understand the importance that Eeva can have in embryo selection, it is necessary to know how the selection of the embryo or embryos to be transferred to the woman's uterus is usually performed.

From the cohort of embryos available from a patient, the embryologist relies on a series of morphological parameters to establish a classification. This means that the embryologist observes certain characteristics of the embryo at specific moments of embryonic development, which will allow him to decide which embryo has a better quality to be transferred.

Embryo selection by morphology

To perform this observation, it is necessary to remove the embryo from the incubator and take it to the microscope. Thus, the stable culture conditions in which the embryo is kept inside the incubator are interrupted.

Benefits

In addition to the benefit of being able to assess embryo viability early, the Eeva system has other advantages, which are mentioned below.

Objective method of selection

Traditional embryo selection by morphology is subjective, which means that the evaluation of an embryo may be different depending on the embryologist who evaluates it.

However, the Eeva test allows an objective evaluation of embryos based on certain parameters included in its algorithm. Therefore, Eeva can reduce the variability of embryo evaluations among embryologists to predict developmental potential to blastocyst.

More stable conditions

Due to the time-lapse system, embryos do not have to leave the incubator to be evaluated under a microscope. This reduces its handling and the likelihood of an accident, but also allows the embryo to be unaffected by changes in culture conditions that occur during its conventional evaluation outside the incubator.

Embryo selection with time-lapse

On the other hand, the time-lapse system allows continuous monitoring of the embryos; whereas conventional evaluation is performed only at certain specific moments of embryo development to avoid removing the embryo from the incubator. Therefore, much more information about embryonic development can be obtained with time-lapse systems.

Possibility of reducing multiple pregnancy

Since the Eeva system makes it possible to choose with greater certainty the embryo with the greatest developmental capacity, the tendency to transfer a single embryo to the patient is favored. This would lead to a reduction in the rate of multiple pregnancy, which is associated with risks for both mothers and babies.

Effectiveness of Eeva

Eeva has shown that, in conjunction with morphological selection, it is more effective in determining which embryos will be able to reach blastocyst than if analyzed by morphology alone. In addition, embryo evaluation with Eeva has also been shown to improve implantation and pregnancy rates.

However, some studies have observed no difference in pregnancy rates with the use of Eeva compared to the usual morphological selection method.

FAQs from users

What other types of incubators are available for embryo culture?

The first incubators for embryo culture were large and the embryos of all patients were stored in the same space. Therefore, when a patient's embryos had to be removed for microscopic viewing or transfer, the temperature and gas conditions were temporarily altered, and this could affect all the embryos.

More recently, "benchtop" or "sandwich" type incubators have been developed. These have individualized compartments for each patient, so that opening one does not affect the others. In addition, the culture conditions are much better than with the first incubators, as they work at low oxygen pressures, so they imitate the conditions of the human body much better. The difference between these incubators and the Embryoscope® or other types of time-lapse incubators is that they do not have a built-in camera, so if you want to monitor the development of the embryos you need to remove them from the incubator to look at them under the microscope.

Are there other Time-Lapse incubators?

Yes, the most common Time-Lapse systems are currently classified into two types depending on the imaging system:

Built-in image system

Embryoscope, Geri, Miri and CCM.

Standalone image system

PrimoVisio and Eeva

Cada sistema Time-Lapse tiene sus propias ventajas y propiedades específicas, aunque disponer de cualquier información del desarrollo de los embriones permite una evaluación más precisa de los mismos. Así, se aumenta la tasa de implantación embrionaria y, por tanto, la probabilidad de embarazo.

What are the indications for the Eeva test?

Eeva has no indication as to the characteristics of the patient or the IVF technique used. Any patient can benefit from its advantages.

What is the price of the Eeva test?

The cost of embryo culture in time-lapse incubators is higher than if traditional incubators are used.

Time-lapse embryo culture usually involves an extra cost of 300-500 euros compared to the price with traditional culture. However, the exact price of time-lapse embryo culture will depend on each fertility clinic.

Recommended readings

If you wish to obtain more information about embryo classification, you can click on the following link: Classification of embryos according to their day of development.

If, on the other hand, you are interested in time-lapse systems, we recommend you to read this article: What is time-lapse - Enhancement of in vitro embryo development

References