A monochorionic monoamniotic (MCMA) twin pregnancy is a subtype of monozygotic twin pregnancy. These fetuses share a single chorionic sac, a single amniotic ...×ArticlesLogInCasesSignUpCoursesQuizDonateAbout×MenuSearchADVERTISEMENT:Radiopaediaisfreethankstooursupportersandadvertisers.BecomeaGoldSupporterandseenoads.ArticlesCasesCoursesLogInLoginSignup{"url":"/signup-modal-props.json?lang=us\u0026email="}ArticlesCasesCoursesQuizAboutRecentEditsGoad-freeSearchMonochorionicmonoamniotictwinpregnancyDrDanielJBell◉andDrYurangaWeerakkody◉etal.Amonochorionicmonoamniotic(MCMA)twinpregnancy isasubtypeofmonozygotictwinpregnancy. Thesefetusesshareasinglechorionicsac,asingleamnioticsac,and,ingeneral,asingleyolksac. Onthispage:Article:EpidemiologyPathologyRadiographicfeaturesTreatmentandprognosisSeealsoRelatedarticlesReferencesImages:CasesandfiguresEpidemiologyItaccountsfortheminority(~5%)ofmonozygotictwinpregnanciesand~1-2%ofalltwinpregnancies.Theincidenceis~1in10000ofallpregnancies2.AssociationsThistypeofpregnancycarriesarelativelyhighincidenceofcongenitalanomalies4.PathologyItresultsfromaseparationofasingleovumat~8-13daysfollowingformation(i.e.laterthanwithanMCDApregnancy). Bythistimeatrophoblasthasalreadyformed,yieldingasingleplacenta. Thesefetusesshareasinglechorionicsac, asingleamnioticsac, andmostoftenasingleyolksac. Thetwinsareidentical(andofcourseofthesamegender). RadiographicfeaturesUltrasoundFirsttrimestershowsatwinpregnancywithasinglegestationalsacandamostoftenasingleyolksac(whichhelpstodifferentiatefromaDCDAandMCDApregnancy)thereisnointer-twinmembrane:theoretically,thisdifferentiatesfromaDCDAandMCDApregnancyhowever,eveninanMCDApregnancy,theintertwinmembranemaybedifficulttoseethereforenon-visualizationoftheintertwinmembraneisnotinitselfdiagnosticSecondtrimesterFeaturesnotedonasecond-trimesterscanincludes:specifictoanMCMApregnancytherecanbethepresenceofcordentanglementtherecanbethepresenceofcordfusionabsentinter-twinmembrane:althoughmaybedifficulttoseesometimesevenwith