Do human concepti have the potential to enter into diapause?

Although there is no direct evidence as to whether human concepti have the potential to enter into diapause before implantation, the possibility that human concepti may be capable of following this developmental pathway if exposed to an appropriate environment cannot be ruled out. Direct evidence remains elusive because of the ethical restraints associated with research activities within this area of knowledge. If conceptus diapause has evolved in primates and persists at the present time despite its apparent limited or no adaptive advantage, artificial induction of diapause in humans may have clinical implications for increasing: (i) the viability of concepti after biopsy, freezing-thawing or any other experimental procedure that tends to decrease cell numbers or division rate of concepti; and (ii) the relatively low implantation rates obtained at the present time after uterine transfer of human concepti fertilized in vitro. Furthermore, conceptus diapause may be a good paradigm to understand the interplay between the different genetic/molecular components of both the conceptus and endometrium at implantation.