简介：Thisreviewbeginswithabriefcommentaryonthediversityofplacentationmechanisms,andthengoesontoexaminetheextensivealterationswhichoccurintheplasmamembraneofuterineepithelialcellsduringearlypregnancyacrossspecies.Ultrastructural,biochemicalandmoregeneralmorphologicaldatarevealthatstrikinglycommonphenomenaoccurinthisplasmamembraneduringearlypregnancydespitethediversityofplacentaltypes-fromepitheliochorialtohemochorial,whichultimatelyformindifferentspecies.Toencapsulatetheconceptthatcommonmorphologicalandmolecularalterationsoccuracrossspecies,thattheyarefoundbasolaterallyaswellasapically,andthatmoreovertheyareanongoingprocessduringmuchofearlypregnancy,notjustaneventatthetimeattachment,braneduringearlypregnancyarekeytouterinereceptivity.