By performing endometrial biopsy it is possible to study in more detail the state of the endometrium and its receptivity.
On the one hand, the ERA endometrial receptivity test allows us to study the genes expressed by the endometrial cells at a certain point in the cycle and thus know when it is the ideal time to perform an embryo transfer. Electronic microscopy also allows us to see the appearance of extensions on the surface of endometrial cells called pinopods that have been associated with the best time to implant.
On the other hand, the EMMA and ALICE tests are used to study the intrauterine microflora and find out if there is an adequate proportion of microorganisms or, on the other hand, if there is an altered microbial profile. The ALICE test is also used to diagnose chronic endometritis.
At the same time, specialists in assisted reproduction, through the ultrasound study of the uterus and endometrium, look for sonographic and doppler criteria that guide a greater or lesser receptivity of the uterus.
Endometrial thicknesses greater than 8 mm, the appearance of intraendometrial vessels on the day of embryo transfer and endometrial volumes greater than 2.5 ml are the current parameters published in the literature that indicate good uterine receptivity.