Why Embryos Do Not Implant?
By Francis Polansky, M.D.
It happens all the time: gamete embryologists assess embryo quality just before embryo transfer and judge them to be excellent. One or more of the embryos are transferred into the uterus and – two weeks later – the pregnancy test is negative. What happened? What went wrong with the uterus that it prevented the embryos from implanting?
It is all too easy to blame the uterus, the receptivity of one’s body, or the hormonal environment for implantation failure. The truth of the matter is, there is no accurate way to assess the true embryo quality. So even if the embryologists really like the embryos, it is far from certain that they are biologically "perfect". And only a biologically "perfect" embryo can successfully implant and continue to develop to a healthy baby.
The receptivity of the uterus does not have a profound effect on the success of infertility treatments. There is evidence suggesting that the role of the uterine lining receptivity as a decisive factor in human conception is limited. Since women can have ectopic pregnancies (tubal, ovarian, cervical, abdominal), embryos seem to be able to implant in environments that would be considered hostile.
For many years it has been evident that the probability of success of Donor Egg IVF treatments depends primarily on the donors’ egg quality, and that the age of the recipient mother or her uterine receptivity is not an important factor.
Contemporary data suggests that a pregnancy outcome is determined at the moment of the creation of an embryo (the moment of fertilization), and that the subsequent pregnancy events (embryo hatching, implantation and further fetal development) are merely playing out of this predetermined outcome. Embryo quality is the pivotal factor in a successful reproductive outcome.
Current reproductive medicine research and clinical experience point at the possibility of less than ideal synchronization between developing embryos and the development of the endometrial lining in treatments that include ovarian stimulation (IVF).
Close monitoring of hormonal levels during ovarian stimulation can uncover treatment cycles where such lack of synchronization is likely to occur. Under these circumstances, all created embryos are cryopreserved and subsequently transferred into the uterus as cryopreserved-thawed embryos (Delayed Embryo Transfer). This approach achieves perfect embryo-endometrial lining synchronization.