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1、最新医学遗传学17出生缺陷-药学医学精品资料Birthdefectsaredefinedasabnormalitiesofstructure,function,orbodymetabolismthatarepresentatbirth.1.GeneralOneofthemostcommonworriesforexpectantparentsisthatsomethingwillbewrongwiththeirbaby.Somedefectsareoftennotdiscovereduntillater(egdeaf
2、nessandproblemsinwalking).Thereisconsiderableregionalvariationintherateofdefectsseenatbirth.GlasgowandDublinhavetraditionallybeenblackspots,withratesover3percent,butthesefiguresarefalling.Thenumberofbabiesactuallybornwithdefectsisalsomarkedlyaffectedbytheavail
3、abilityofprenatalscreening,andtheavailabilityofvoluntaryterminationofpregnancyinthecaseofsevereabnormalities.2.FormsofBirthDefectsDefectsoflimbs,heartandspinalcordrepresentabouthalfofallabnormalities.Themostcommonkindsofdefectarethoseaffectingthelimbs(armsandl
4、egs).Theseincludemissingorextrafingersortoes,deficienciesinlimblength,andabnormalitiesinpositioning,suchasclubfoot.Heartabnormalitiesrepresentthenextmostcommoncategoryofdefect.Commonheartdefectsinclude'holesintheheart'wherebloodcanpassfromonesideofthehearttoth
5、eother.Again,thesemaynotallbedetectedatbirth.Thethirdmostcommonkindofdefectaffectsthespinalcord,suchasspinabifida.Otherdefectscommonlyobservedincludethoseaffectingtheface(suchascleftlipandpalate),problemswiththedevelopmentoftheintestinesandstomach,andproblemsa
6、ffectingthesexualorgans.MajorchromosomalproblemssuchasDown'ssyndrome(Trisomy21)arefoundinabout0.15percentofbirths(aboutthreebabiesinevery2000).3.ThecauseofbirthdefectsA.GeneticsGeneticsplayaroleinsomebirthdefects.Onemissingorfaultygenecancauseabirthdefect.Inan
7、cienttimes,abnormalitieswereseenaswarningsorpunishmentsfromthegods.Evenquiterecently,itwasbelievedthatspecificeventsduringthepregnancy-suchasbeingfrightenedbyamouse-wouldleadtospecificdefectsinthebaby,egamouseshapedbirthmark.Suchfolkbeliefsstillpersistinplaces
8、.However,mostdefectsthatcanbetracedtoasinglecausehaveageneticorigin.Thisdoesnotnecessarilymeanthattheparentssufferfromthesamedefect.Itmaybethattheyarecarriersofthecondition,orthatt
