SkiptomaincontentHomePregnancyFindingoutyou'repregnantBacktoFindingoutyou'repregnantPregnantwithtwinsFertilitytreatmentsandthefactpregnanciesarehappeninglaterinlifehasmademultiplebirthsmorecommon.DifferenttypesoftwinsOne-thirdofalltwinswillbeidenticalandtwo-thirdsnon-identical.IdenticaltwinsIdentical(monozygotic)twinshappenwhenasingleegg(zygote)isfertilised.Theeggthendividesin2,creatingidenticaltwinswhosharethesamegenes.Identicaltwinsarealwaysthesamesex,soifyourtwinsareidentical,you'llhave2girlsor2boys.Non-identicaltwinsNon-identical(dizygotic)twinshappenwhen2separateeggsarefertilisedandthenimplantintothewomb(uterus).Thesenon-identicaltwinsarenomorealikethananyother2siblings.Non-identicaltwinsaremorecommon.Thebabiesmaybeofthesamesexordifferentsexes.Areyoucarryingtwins?Youmightthinkyou'recarryingmorethan1babyif:youseembiggerthanyoushouldbeforyourdatestwinsruninyourfamilyyouhavehadfertilitytreatmentIt'susuallypossibletofindoutifyou'rehavingtwinsthrough12-weekscan.Atthescan,youshouldbetoldwhetherthebabiesshareaplacenta(meaningthey'reidentical)oriftheyhave2separateplacentas(meaningtheycanbeidenticalornot).Ifthisisnotclearfromthefirstscan,youshouldbeofferedanotherone.Whatcausestwins?Nobodyknowswhatcausesidentical(monozygotic)twins.Everyonehasthesamechanceofhavingidenticaltwins:about1in250.Identicaltwinsdonotruninfamilies.Buttherearesomefactorsthatmakehavingnon-identicaltwinsmorelikely:non-identicaltwinsaremorecommoninsomeethnicgroups,withthehighestrateamongNigeriansandthelowestamongJapaneseifyou’repregnantandover35you’remorelikelytohavenon-identicaltwinsbecauseyou’remorelikelytoreleasemorethan1eggduringovulationnon-identicaltwinsrunonthemother'ssideofthefamily,probablybecauseofaninheritedtendencytoreleasemorethan1eggIVF canincreasethechanceoftwins,asmorethan1embryomaybetransferred.HowcanItellifmytwinsareidentical?ThemostaccuratewaytotelliftwinsareidenticalisthroughaDNAtest.Thiscanonlybedoneafteryourbabiesareborn.Theplacentacouldalsoprovideclues.Ifyourfirstultrasoundscani