Scientific research and advances in techniques and treatments have made it possible, in recent decades, to increase the number of babies born through assisted reproduction. The clinical and culture conditions for obtaining quality embryos are currently very advanced.
However, sometimes there are losses due to biochemical miscarriages or implantation failures despite having high quality embryos. This has caused professionals in the field to focus for years on how to help improve implantation in in vitro fertilisation (IVF) treatments (1).
After many studies, it was discovered that endometrial receptivity was one of the main obstacles to achieving pregnancy. Today, after numerous advances, they are able to calculate the exact moment when the endometrium is most receptive for implantation. This has been coined the term window of implantation. During this period, the endometrium has already acquired the morphological and functional characteristics necessary for the embryo to adhere to it and implant (2).
This phenomenon normally begins between 5 and 7 days after ovulation has occurred. However, there may be cases in which the window of implantation is displaced and does not occur on these specific days, resulting in a problem of infertility. Endometrial receptivity is essential to achieve pregnancy. Even if we obtain embryos of very good quality, if they are transferred at the wrong time in the cycle, implantation failure is likely to occur (2).
What is the ERA test?
The ERA test, also known as the endometrial receptivity test, is a molecular diagnostic test used to determine the receptivity status of the endometrium (3).
This test makes implantation failures less likely to occur in in vitro fertilisation (IVF) treatments. This test makes it possible to determine the most suitable day for embryo transfer, thus increasing the likelihood of pregnancy (3). Therefore, for those patients who have suffered embryo implantation failure, it will be necessary to undergo this test.
How is the ERA test performed?
Scientific studies and advances in the behaviour of the endometrium have led to the success of the ERA test.
These scientific advances have made it possible to study in detail how the endometrium behaves in the different phases. Today, with delayed transfer, the endometrium can be analysed in order to improve uterine conditions for implantation. However, routine clinical practice is limited to ultrasonography, which offers the advantage of being a non-invasive method.
The ultrasonographic parameters to be studied are the endometrial pattern, thickness, delimitation with the myometrium, myometrial contractility and uterine perfusion, the first two being the most important.
After evaluating these parameters, results are obtained to determine whether the endometrium is receptive for transfer.
What is the benefit of the ERA test?
Due to the accuracy and functionality of the ERA test, there are several benefits to this test.
Knowing exactly the right times for the window of implantation avoids making embryo transfers blindly and without being sure of approaching success.
In addition, it ostensibly increases the chances of becoming pregnant and thus avoids further implantation failures that would cause frustration, fear and uncertainty in the process.
References
- Fundación medicina fetal Barcelona. Pérdida gestacional de primer trimestre [Internet]. [cited 2020 May 5]. Available from: https://medicinafetalbarcelona.org/protocolos/es/obstetricia/perdida-gestacional-primer-trimestre.html
- Reproducción Asistida ORG. (s. f.). Test de receptividad endometrial (ERA). https://www.reproduccionasistida.org/test-receptividad-endometrial-test/#ventana-de-implantacion
- Gómez E, Ruíz-Alonso M, Miravet J, Simón C. Human Endometrial Transcriptomics: Implications for Embryonic Implantation. Cold Spring Harb Perspect Med. 2015 Mar 27;5(7):a022996.