The presence or absence of lambda sign, T-sign, dividing membrane thickness and number of placentae were used to determine chorionicity.HomePregnancyMedicineObstetricsTwinsArticlePDFAvailableLiteratureReviewThelambda(twinpeak)signJuly2018AbdominalRadiology43(7)DOI:10.1007/s00261-017-1356-4Authors:TsunWaiJeffreyWuTsunWaiJeffreyWuThispersonisnotonResearchGate,orhasn'tclaimedthisresearchyet.Yan-LinLiQueenMaryHospitalKinHoiWongDownloadfull-textPDFReadfull-textYou'redownloadingafull-textprovidedbytheauthorsofthispublication.Apreviewofthisfull-textisprovidedbySpringerNature.Downloadfull-textPDFReadfull-textDownloadcitationCopylinkLinkcopiedReadfull-textDownloadcitationCopylinkLinkcopiedCitations(1)References(2)Discovertheworld'sresearch20+millionmembers135+millionpublications700k+researchprojectsJoinforfreePublicFull-text1PublisherPreview1ContentuploadedbyYan-LinLiAuthorcontentAllcontentinthisareawasuploadedbyYan-LinLionOct23,2017Contentmaybesubjecttocopyright.Thelambda(twinpeak)signTsunWaiJeffreyWu,1Yan-LinLi,2Kin-HoiWong21LiKaShingFacultyofMedicine,UniversityofHongKong,HongKong,China2DepartmentofRadiology,QueenMaryHospital,UniversityofHongKong,K3,102PokfulamRoad,HongKong,ChinaThelambdasignreferstothetriangularprojectionofchorionbetweenthelayersofinter-twinmembraneswhichresemblestheGreekalphabet‘‘lambda’’(Fig.1).Itisbestobservedbetween10and14weeksofgestationonpelvicsonography,anditspresenceishighlysugges-tiveofdichorionicdiamniotic(DCDA)twinpregnancy(Fig.2).Thefuseddichorionicplacentaalsoassumestheappearanceofamountaintopbetweenthetwingesta-tionalsacs;thusthemetaphoricalsourceofitsalternatetitle,the‘‘twinpeak’’sign(Fig.3)[1].CompliancewithethicalstandardsFundingNofundingwasreceivedforthisstudy.ConflictofinterestTheauthorsdeclarethattheyhavenoconflictofinterest.EthicalapprovalThisarticledoesnotcontainanystudieswithhumanparticipantsoranimalsperformedbyanyoftheauthors.InformedconsentStatementofinformedconsentwasnotapplicablesincethemanuscriptdoesnotcontainanypatientdata.Ref