Thisreviewbeginswithabriefcommentaryonthepersityofplacentationmechanisms,andthengoesontoexaminetheextensivealterationswhichoccurintheplasmamembraneofuterineepithelialcellsduringearlypregnancyacrossspecies.Ultrastructural,biochemicalandmoregeneralmorphologicaldatarevealthatstrikinglycommonphenomenaoccurinthisplasmamembraneduringearlypregnancydespitethepersityofplacentaltypes-fromepitheliochorialtohemochorial,whichultimatelyformindifferentspecies.Toencapsulatetheconceptthatcommonmorphologicalandmolecularalterationsoccuracrossspecies,thattheyarefoundbasolaterallyaswellasapically,andthatmoreovertheyareanongoingprocessduringmuchofearlypregnancy,notjustaneventatthetimeattachment,braneduringearlypregnancyarekeytouterinereceptivity.
