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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

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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.
It can be inferred from the fourth paragraph that______.
选项 A、taking daily multivitamins is not as common a practice among women who are not pregnant as among pregnant women in the United States
B、pregnant women consider taking multivitamin as the most important way to guarantee their nutrition intake
C、women who are not pregnant do not think taking multivitamins can reduce the risk of birth complications
D、pregnant women in the United States believe that taking multivitamins can reduce the risk of birth complications
答案A
解析 第四段以另一项研究为例，说明服用多种维生素是美国孕期妇女的一种普遍做法，并对比了服用维生素的比例在孕期妇女和未怀孕妇女两者间的差别。明显可以推断出未怀孕妇女服用维生素的做法不如孕期妇女服用维生素那么普遍，即A选项。BD属于过度推论，孕期妇女服用维生素比例高并不能说明她们认为这是保证她们营养摄入的最重要方法或者这样做可以减少分娩综合征的风险，因此BD错误。同理，C也属于过度引申，未怀孕妇女服用多种维生素的比例比较低并不能说明她们不认为服用多种维生素可以减少分娩综合征的风险，因此也不正确。
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