Why Embryos Do Not Implant
By Francis Polansky, M.D.
It is a common misconception to believe that as long as an embryo is transferred (deposited) inside the uterus in IVF treatment, there will be a baby.
An IVF treatment cycle proceeds along several milestones. The ovaries must respond to stimulation, eggs must be retrieved, eggs must fertilize, embryos must develop normally, an embryo must be available for transfer, it must hatch out and implant, and the pregnancy must successfully proceed to a live birth. This can be a "tall order".
Most IVF treatment cycles will result in one or two embryos transferred inside the uterus, and most of them will not result in a live birth. This is Mother Nature. The majority of human embryos, whether created through intercourse, artificial insemination, or In Vitro Fertilization, are less than biologically "perfect" and do not have the potential to result in live births.
IVF embryologists assess embryo quality just before embryo transfer and may judge them to be of high grading, but there is no accurate way to know the true embryo quality. Even if the embryologists embryo assessment is high, it is not certain that they are biologically "perfect".
If, after an embryo transfer, the pregnancy test is negative, it is then all too easy to blame the uterus, the receptivity of one's body, or the hormonal environment for the implantation failure.
The receptivity of the uterus does not have a profound effect on the success of infertility treatments. Since women can have ectopic pregnancies (tubal, ovarian, cervical, abdominal), embryos seem to be able to implant in environments that would be considered less than optimal or even hostile.
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 this already-decided outcome. Embryo quality is thus the pivotal factor in the success of reproductive treatments.