This is a frequent question. We professionals discuss in our meetings, but Carla Simone showed that the window of implantation doesn’t change for up to two years. So recently, I also had a clinical situation where the patient came with a diagnosis of a recurrent implantation failure so we determined the window of implantation and endometrium was pre-receptive. So we prescribed her progesterone for 9 days and she got pregnant, she successfully delivered and she came back two years later. So we also discussed with her the situation of examining the window of implantation again, and she agreed. We repeated the test, and we noticed that the window of implantation was pre-receptive again, so we had to delay our embryo transfer. The difference between those two tests was three years. That is only one clinical case where it looks like it can be different. So in any clinical setting, we have to discuss it with the patient.
Well, implantation a window the has to be the synchronization of both: embryo and endometrium, so when we have an embryo on day 5 (which is a blastocyst), we need to have 5 days of progesterone to make them both synchronized to actually to proceed with the implantation from the embryo into the endometrium. So it’s not like it lasts forever, you just give five days of progesterone while transferring embryos on day 5 and you know that you are okay.
