Both slowly developing embryos and a variable pace of luteal endometrial progression may conspire to prevent normal birth in spite of a capable embryo

Embryonic implantation requires synchrony between the endometrium and the embryo.

Jason M. Franasiak, M.D., Maria Ruiz-Alonso, M.Sc., Richard T. Scott, M.D., Carlos Simón, M.D., Ph.D.

Volume 105, Issue 4, Pages 861-866


Embryonic implantation requires synchrony between the endometrium and the embryo. When analyzed in isolation, competent embryos may be unsuccessful when placed on a nonreceptive endometrium or vice versa, contributing to the “black box” of implantation failure. It is when the two are assessed together that dyssynchrony becomes evident, due to premature progesterone stimulus on the endometrium, physiologic displacement of the window of implantation or late blastulation of the embryo, or all combined. From the embryonic component, detailed assessment of the timing of blastulation is essential. The molecular diagnosis of endometrial receptivity based on its transcriptomic signature could be superior to other techniques used in the past for defining the endometrial window of implantation.

  • This article examines the hugely important concept of embryo-endometrial synchrony. I read with great interest that some studies suggested that “poor outcomes with late-blastulating embryos have been due in large part to dyssynchrony, not to intrinsic deficits in embryonic reproductive competence”. I would still assume that late-blastulating embryos are less likely to be euploid than embryos blastulating on schedule, even when controlled for age. Is this the case? If yes then I would assume the authors recommend PGS when correcting the dyssynchrony through cryopreservation of late-blastulating embryos?

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