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  3. Taking a multivitamin around the time of conception may help women lower their risk of delivering low-birth-weight babies, a new

Taking a multivitamin around the time of conception may help women lower their risk of delivering low-birth-weight babies, a new

admin2016-08-02  32
问题     Taking a multivitamin around the time of conception may help women lower their risk of delivering low-birth-weight babies, a new research shows. The study, one of the first to look at multivitamin use immediately before and after conception, strengthens the notion that nutritional deficiencies may increase the risk of birth complications.
    Still, the researchers cautioned that it was too soon to recommend multivitamins for women who are contemplating pregnancy or already expecting. While some studies have suggested benefits, others have found that women who eat a healthy diet have no need for multivitamins, and that vitamins may even do some harm, especially when their use is continued late into a pregnancy.
    The study, published in the September issue of The American Journal of Clinical Nutrition, analyzed data on nearly 36,000 Danish women enrolled in a national birth registry. The scientists who carried out the research found that a large share of the women—about 60 percent had been taking multivitamins in the four weeks before and eight weeks after the last menstrual period. After adjusting for a number of risk factors, like smoking, weight and the age of the mother, the study found that women who took a daily multivitamin and were of normal weight had a nearly 20 percent lower chance of delivering a preterm baby, compared with those who did not take a daily multivitamin. Women who were overweight did not see the same benefit, though it was unclear why.
    In 2004, a study by scientists at Emory University and the Centers for Disease Control and Prevention found that taking daily multivitamins was a widespread practice among expectant mothers in the United States. Up to 78 percent of pregnant women reported taking multivitamins, the study found, compared with only 47 percent of women who were not pregnant.
    Doctors have long encouraged pregnant women and those contemplating pregnancy to take folic acid—a B vitamin—daily to help prevent neural tube defects. Folic acid is the synthetic form of folate, a member of the family of B vitamins that is involved with DNA synthesis and DNA methylation. Because of these crucial functions, folate plays important roles in fetal development and nerve tissue health. And since the late 1990s, the government has also required food makers to add the vitamin to many grain products, including flour and breads. The authors of the latest study suggested that there could be other nutrients in multivitamins besides folic acid that help reduce the risk of birth complications. But they also said that more, research was needed, and that they were not recommending that women trying to conceive should start a daily multivitamin regimen.
According to Paragraph 3, the factor combined with taking multivitamins to decide women’s chance of delivering a preterm baby is______.
选项 A、smoking
B、weight
C、age of the mother
D、last menstrual period
答案B
解析 本题考查考生对第四段中有关影响产妇分娩早产儿几率的因素的理解。ABC这三个选项一吸烟、体重和产妇年龄都是其影响因素，但是文中特别提到每日服用多种维生素剂而且体重正常的妇女，比那些没有每天服用多种维生素剂的妇女，减少20％的可能性产出早产婴儿。体重超标的妇女没有发现同样的好处。可见只有体重是文中专门指出与服用多种维生素联合作用可以决定产妇分娩早产儿几率的因素，因此选B。D并不是影响产妇分娩早产儿几率的因素，更提不上是其决定性因素，也是错误选项。
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