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EMBRYOSCOPE
Today, it is possible to monitor embryos around the clock. With this advancement, division and development stages that were previously missed are no longer overlooked. Especially in situations where single embryo transfer is required, embryo selection gains even greater importance, making it possible to give the patient the highest possible chance of success.
Embryos Under 24-Hour Observation
As is well known, under current conditions the selection of the best-quality embryo for transfer in clinical embryology laboratories is carried out by examining certain morphological characteristics of the embryo under a microscope. These morphological evaluations are performed at specific intervals appropriate to the embryo's division stages. During this process, it is examined whether the embryos meet the necessary conditions. Therefore, when embryo development is assessed using the classical morphological method, only a static observation can be made.
However, embryo development is not a static event but rather a highly complex and dynamic chain of events. Certain clues that could indicate the viability of an embryo cannot be observed through static assessment, and for this reason, although classical morphological evaluation can help guide the selection of the most viable embryo, its predictive value remains limited.
Based on this idea, some medical companies, with support from researchers, have developed a camera-monitor system that can be used either as a module inside incubators where embryos are cultured, or as an integrated part of the incubator itself, allowing embryo development to be examined in detail through continuous 24-hour observations taken at intervals of at least every 5 minutes. This monitor system has made it possible to dynamically examine embryo development.
In this way, the aim has been to reveal, through this technique, certain characteristics that could be important indicators of embryo viability but that cannot be seen with static methods, thereby creating a method with greater predictive value for selecting the most viable embryo. To this end, a number of scientific studies, particularly from European countries, have been published since the late 2000s.
In these scientific studies, the division stages observed during embryo development were evaluated separately (for example, the 1st division stage: the division of the fertilized egg into a 2-cell stage; the 2nd division stage: the division of the 2-cell embryo into 3-4 cells). The time it took for embryos to complete these division stages was compared with the viability of the transferred embryo.
Beyond division timing, it has also been argued that certain specific morphological characteristics, which cannot be clearly observed through static assessment, may also be indicators of embryo viability. However, today, certain details need to be clarified before embryo monitoring systems can be used in practice in all embryology laboratories.
Although some published articles in the literature have demonstrated a beneficial effect, it has not yet been scientifically proven, through prospective comparative studies prepared with correct methodology, that these systems offer a significantly greater advantage over classical embryo evaluation methods in terms of ongoing pregnancy and live birth rates.
Another scientific issue that needs to be clarified regarding monitor systems is the extent to which embryo division stages are affected by external factors (such as the stimulation protocol applied to the patient, details of embryo culture in the laboratory, the culture media used, and temperature variations), and, if they are affected, how these factors change the ideal time intervals for the division stages.
Otherwise, universal standardization of these time intervals will not be possible, and the proposed timing-based scoring system will show variation across different laboratories working with different techniques. Because the cost of embryo monitoring systems is quite high compared to the classical morphological methods currently in use, their routine use in laboratories and complete replacement of classical methods will only become possible once the scientific details mentioned above have been clarified.