title: Embryonic diapause in humans: time to consider?
abstract: BACKGROUND
  When a competent blastocyst stage embryo finds itself in an unreceptive uterus, it delays development. In around one hundred species representing various orders, this delay is known to be reversible, but this phenomenon - termed embryonic diapause (ED) - is not considered a general characteristic of all mammals.
  
  
  OBJECTIVE
  Recently, however, we demonstrated that a non-diapausing species, the sheep, is capable of ED, suggesting the hypothesis that this is in fact an ancestral trait common to all mammals, including humans.
  
  
  METHODS
  In spite of the obvious difficulties in testing this idea, we propose a combination of indirect observations on human fertility patients, and direct study of the embryos of non-human primates.
  
  
  CONCLUSIONS
  Support for our hypothesis would require revision of obstetric interventions routinely performed when a human pregnancy extends beyond the due date.
authors.affiliation: Department of Comparative Biomedical Sciences, University of Teramo, Piazza A, Moro, Teramo 64100, Italy. gptak@unite.it.
authors.forename: Grazyna E
authors.initials: GE
authors.lastname: Ptak
authors.forename: Jacek A
authors.initials: JA
authors.lastname: Modlinski
authors.forename: Pasqualino
authors.initials: P
authors.lastname: Loi
mesh_terms: D000818:Animals; D047108:Embryonic Development; D006801:Humans; D008322:Mammals / Q000196:embryology; D013312:Stress, Physiological; D013997:Time Factors
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