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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

admin2015-09-30  56
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.
Folate plays important roles in______.
选项 A、DNA synthesis and DNA methylation
B、lowering the chance of delivering a preterm baby
C、fetal development and nerve tissue health
D、avoiding vitamin B deficiency
答案C
解析 本题考查考生对最后一段有关维生素里面叶酸这一成分作用的理解。题目有两个关键点．一个是在哪个方面发挥作用，另一个是在这个方面发挥了重要作用，这二者缺一不可。A项DNA的合成和DNA甲基化，文中确实提到叶酸参与DNA的合成和DNA甲基化，但是只是参与，不能得出扮演重要角色，发挥重要作用。因此不正确。B是错误结论，最后一段提到多种维他命中，可能还有其他除叶酸以外的营养成分，能帮助减少分娩并发症的风险，可见叶酸可以帮助减少分娩并发症的风险，但是并没有降低产出早产儿几率，因此B不正确。D属于片面引申，叶酸是维生素B的一种．单单就补充叶酸来说．并不能避免维生素B的缺乏，因此D也不正确。最后一段明确指出由于这些重要的功能，叶酸在胎儿的发育和神经组织的健康方面起着重要的作用，因此C是正确答案。
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