作者:Amy   加入時間:2009-08-04   點擊次數:7264

     Do infertility treatments damage babies'genes? Doctors used to think notNow they are not so sure

  In the 24 years since the birth of Louise Brownthe world's first testtube babythousands of wouldbe parents have been assure that as far as scientists knew there was no extra risk of genetic damage associated with invitro fertilizationor IVFNo matter how sperm meets egg--whether in a woman's body or in a Petri dishand even if the sperm needs some help getting inside the egg--nature is equally vigilant about preventing serious genetic mishaps from coming to termWith those assurancestesttube births have soared from a few hundred a year in the early 1980s to tens of thousands today



  But according to a pair of reports in last week's New England Journal of Medicinethat conventional wisdom may be wrongIn the first studydoctors in Britain and Australia found that infants conceived with both straightforward testtube methods and a more invasive technique called intracytoplasmic sperm in jectionin which sperm is injected directly into the egghave an 8.6% risk of major birth defects--including heart and kidney abnormalitiescleft palate and undescended testicles -- compared with the 4.2% rate in babies made the oldfashioned wayThe second studyconducted by the USCenters for Disease Control and PreventionCDC),reported that babies conceived through what doctors call assisted reproductive technologiesARThave 2.6 times the risk of low or very low birth weight --a significant risk factor for cardiac and cognitive problems


  There are plenty of reasons to take both studies seriouslyIn the lowbirthweight studyfor examplethe researchers allowed for the fact that parents who use assisted reproduction tend to be older than average and to have more multiple births--twinstriplets and so onEven when they corrected for these factorsthe disparity between babies conceived through ART and those conceived normally remained


  But there's no need to panicIndependent experts are quick to point out that the reports are hardly definitiveCouples who seek reproductive help are not just olderthey are also--though it may seem like stating the obvious--infertile"You're comparing two different groups of patients here"says DrWilliam Schoolcraftdirector of the Colorado Center for Reproductive Medicine"You have women with the disease of infertilityand you're comparing them with women who don't have the disease"

  Some of the same caveats apply to the birthdefects studysay expertsHeretooearlier research had found no significant differences between testtube babies and conventionally conceived kidsAnd hereagainthe new study didn't correct for the fact that women who get reproductive assistance often have something wrong with their reproductive system in the first place



  Even if these new studies are borne out by later research--already under way in infertility programs in Australia and the US--the risks to kids conceived by assisted reproduction remain reassuringly smallAnd even if the danger is twice what doctors previously believed91% of ART babies would still be born perfectly healthySays DrZev Rosenwaksdirector of New York Presbyterian Hospital's infertility program"If you ask a couple if they would rather not have a child at all or try to have a child that over 90% of the time will be normalI think they will choose to have the child"



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