Most patients naively expect that the success rate in an IVF cycle is 100%. After all, if the doctor is actually making the embryo in the laboratory, then isn't it a certainty that the embryo will become a baby once it's put back into the uterus ? After all, it's then just a question of the embryo sticking to the uterus, and if my uterus is normal, then I am sure to get pregnant !
I wish life was that simple !
Unfortunately, embryo implantation is a complex biochemical process which involves the interplay of signals between the embryo and the uterine lining. We don't understand too much about this process and cannot control it at all.
When an IVF cycle fails, we glibly tell the patient that the reason is - Your embryos failed to implant. Actually, this is just a way of covering up our ignorance. Embryo implantation is still a "black box" into which we have very limited insight. When you think about it, what we are doing is transferring a microscopic ball of cells into the uterus. We really have no way of tracking its fate or figuring out why it did not "stick", once we have done so.
When doctors tell patients that their problem is " failed embryo implantation", patients are quite hopeful. Now that the doctor "knows" what the problem is, he will be able to fix it. Actually, Failed Implantation is a "waste paper basket" diagnosis. While it's a convenient short-hard term when discussing IVF outcomes with patients, in reality it tells us very little about what went wrong; why it went wrong: or what we can do about it. However, labelling it as failed implantation gives patients the impression that we know what's happening and are in control of the situation !
The problem is that patients start feeling that their body is " rejecting" the embryo; or that they did something wrong, as a result of which the embryo " fell out." It's just that human reproduction is not a very efficient enterprise, and this is true, whether embryos are being made in the bedroom or in the IVF lab !