2. 外语
  3. In the 24 years since the birth of Louise Brown, the world’s first test-tube baby, thousands of would-be parents have been assur

In the 24 years since the birth of Louise Brown, the world’s first test-tube baby, thousands of would-be parents have been assur

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问题     In the 24 years since the birth of Louise Brown, the world’s first test-tube baby, thousands of would-be parents have been assured that as far as scientists knew there was no extra risk of genetic damage associated with in-vitro fertilization (试管内受精). With those assurances, test-tube 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 Medicine, that conventional wisdom may be wrong. In the first study, doctors in Britain and Australia found that infants conceived with both straightforward test-tube methods and a more invasive technique in which sperm is injected directly into the egg, have an 8.6% risk of major birth defects—including heart and kidney abnormalities—compared with the 4.2% rate in babies made the old-fashioned way. The second study, conducted by the US Centers for Disease Control and Prevention, reported that babies conceived through what doctors call assisted reproductive technologies (ART)have 2.6 times the risk of low or very low birth weight—a significant risk factor for heart disease and cognitive problems.
    There are plenty of reasons to take both studies seriously. In the low-birth-weight study, for example, the researchers allowed for the fact that parents who use assisted reproduction tend to be older than average and to have more multiple births—twins, triplets and so on. Even when they corrected for these factors, the disparity (差异)between babies conceived through ART and those conceived normally remained. But there’s no need to panic. Independent experts are quick to point out that the reports are hardly definitive. Couples who seek reproductive help are not just older; they are also infertile. "You’re comparing two different groups of patients here," says Dr. William Schoolcraft, director of the Colorado Center for Reproductive Medicine. "You have women with the disease of infertility, and you’re comparing them with women who don’t have the disease."
    Some of the same caveats apply to the birth-defects study, say experts. Here, too, earlier research had found no significant differences between test-tube babies and conventionally conceived kids. And here, again, the 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 ART remain reassuringly small. And even if the danger is twice what doctors previously believed, 91% of ART babies would still be born perfectly healthy.
The number of test-tube births has surged greatly for 24 years because______.
选项 A、test-tube technique offers more multiple births: twins and triplets and even more
B、couples prefer in-vitro fertilization to conventional conceiving
C、scientists have assured that no risk of genetic damage is involved
D、the technique has matured and perfected to a large extent
答案C
解析 细节推断题。定位句提到，正因为有了科学家的保证，即上句提到的试管内受精不会对基因造成破坏，试管婴儿才上升到如今的每年数万个。因此答案为C)。
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