**4. It's the Quality of the Soil, Not the Seed**

Successful implantation is the end result of a complex molecular interaction between two separate components: a viable blastocyst and an appropriately primed endometrium [2,6,23]. Both are important, but do they contribute equally to reproductive disorders? Much attention has focused on the blastocyst, and, indeed, many early miscarriages do result from karyotypic abnormalities within the blastocyst [24]. However, there is increasing evidence to suggest that appropriate priming of the soil (endometrium)—a process known as decidualization—may contribute more to reproductive disorders than the quality of the seed (embryo). Observations in support of this argument include:


Taken together, these data suggest that the endometrial "window of implantation" is independent of the blastocyst and that the embryo is not the rate-limiting factor for implantation, but rather the synchronization between them.
