点击显示 收起
根据1月11日的每周死亡率与发病率报告中所登载的调查结果，生产前摄取叶酸与婴儿的神经管缺陷发生率有关。
疾病控制和预防中心的L. Alvelo-Maldonado医师和同事表示，出生时的缺损是美国和波多黎各婴儿死亡率的主要原因，神经管缺损(NTDs)是严重的脊椎与脑部出生缺损；最常见的两种NTD是脊柱分裂和无脑症，在怀孕前和怀孕早期摄取叶酸可以预防NTD。
美国NTD的流行病学，西班牙后裔者高于非西班牙后裔白人或者非西班牙后裔黑人妇女；美国的NTD发生率低于大多是西班牙裔居民的波多黎各，该国的发生率为每10,000新生儿有 8.68 人。
研究者使用1996至2005年间的出生缺陷监控系统(BDSS)和1997至2006年间的行为风险因素监控系统(BRFSS)的资料，分析波多黎各的NTD发生率倾向和摄取叶酸知识之间的关系。
生育年龄妇女知道摄取叶酸知识的百分比从1997到2003年是增加的，但是从2003到2006年是下降；相对的，NTD发生率从1996到2003年是下降的，2003到2005年则是维持稳定。
作者指出，为了继续降低NTD发生率，需要其他方式来增加波多黎各生育年龄妇女摄取叶酸的比率。
BDSS是一项族群基础的主动监控系统，每年评估将近50,000位于波多黎各出生者，BRFSS是一项持续进行的随机拨号电话调查，对象是非收容机构中的18岁以上公民，7年的调查期间，共调查了6356位妇女。
摄取叶酸的定义为每日摄取含有叶酸的维他命药丸或补充品，知道叶酸相关知识的定义，是由健康照护人员建议摄取叶酸以预防出生缺陷；波多黎各每年发生的NTD从1996年的93 (每10,000活产14.7)降到2003年的27 (每10,000活产5.3) (P < .05)，2004年为40 [每10,000活产7.8] ，2005年为44 [每10,000活产8.7]。
这段期间，18-44岁的未怀孕妇女，摄取叶酸的比率从1997年的20.2%增加到2003年的30.9%，之后在2006年增加到24.8%；而知道叶酸相关知识的比率则是从1997年的22.4%增加到2003年的72.0%，以及在2006年降为56.5%。
2006年时，教育程度越高以及家庭收入越高的妇女，比较可能具有叶酸相关知识和每日摄取叶酸补充品。
一篇伴随而来的编辑评论指出，波多黎各近几年来，NTD缺损的结果(例如脊柱分裂和无脑症)已经引起关注；1996至2003年间的发生率降低是因为有妇女摄取叶酸的宣导活动，以及于1998年从美国引进含有叶酸的榖类制品；1997至2003年这段期间，波多黎各妇女摄取叶酸以及知道相关知识的比率是增加的，而在2003至2006年间则是下降。
这些研究发现的限制是，BRFSS调查对象仅仅包括非收容机构且有一般有线电话的人，BRFSS有关叶酸摄取的问题并未明确说明每日建议剂量，仅提及维他命补充品，可能无法代表所有的NTD，其发生率低，也可能受到不同监控方法的影响。
编辑指出，叶酸宣导活动在波多黎各继续进行中，倡导健康事务以及其他教育议题；不过，尽管有这些方法，波多黎各仅约有四分之一的生育年龄妇女每天摄取含有叶酸的维他命，因此需要其他方式来改善；需要有其他方法了解这些因素，并且提高对叶酸的警觉性，同时建议波多黎各所有生育年龄的非怀孕妇女摄取叶酸。
一篇QuickStats文章描述美国于1991、1995、2000和2005年的脊柱分裂和无脑症比率；1992年开始，美国国家健康促进机构明令生育年龄妇女每天摄取400 μg叶酸，以减少怀孕后造成NTD的风险。
脊柱分裂比率从1995至2000年间的每活产25%，降到2000至2005年间的13%；无脑症比率从1991至1995年减少36%，1995至2005年间则无显著改变。
Knowing Importance of Prenatal Folic Acid May Affect Neural Tube Defect Incidence
By Laurie Barclay, MD
Medscape Medical News
Knowledge of the importance of taking folic acid prenatally may be linked to incidence of infant neural tube defects, according to the results of a survey reported in the January 11 issue of the Morbidity and Mortality Weekly Report.
"Birth defects are one of the leading causes of infant mortality in both the mainland United States and Puerto Rico," write L. Alvelo-Maldonado, MS, and colleagues from the Centers for Disease Control and Prevention, Atlanta, Georgia. "Neural tube defects (NTDs) are serious birth defects of the spine and brain; two of the most common NTDs are spina bifida and anencephaly.... Consumption of folic acid before and during early pregnancy can prevent NTDs."
NTD prevalence in the United States is higher in Hispanic than in non-Hispanic white or non-Hispanic black women. NTD prevalence in the United States is lower than in Puerto Rico, where most residents are Hispanic, and where prevalence is 8.68 per 10,000 live births.
Using data from the Birth Defects Surveillance System (BDSS) for 1996 to 2005 and the Behavioral Risk Factor Surveillance System (BRFSS) for 1997 to 2006, the investigators analyzed trends in prevalence of NTD and in knowledge and consumption of folic acid supplements in Puerto Rico.
Prevalence among women of childbearing age of knowledge and consumption of folic acid increased from 1997 to 2003 but declined from 2003 to 2006. Correspondingly, NTD prevalence decreased from 1996 to 2003 but remained stable from 2003 to 2005.
"To resume the decline in prevalence of NTDs, additional measures might be needed to increase folic acid supplement use among Puerto Rican women of childbearing age," the authors write.
BDSS is a population-based, active surveillance system evaluating approximately 50,000 births in Puerto Rico annually, and BRFSS is an ongoing, random-digit-dialed telephone survey of the noninstitutionalized civilian population aged 18 years and older. During 7 years of surveys, 6356 women were surveyed.
Folic acid consumption was defined as reported daily intake of a vitamin pill or supplement containing folic acid, and knowledge regarding folic acid was defined as knowing that folic acid consumption is recommended by certain health experts to prevent birth defects.
In Puerto Rico, the annual number and prevalence of NTDs decreased from 93 (14.7 per 10,000 live births) in 1996 to 27 (5.3 per 10,000) in 2003 (P < .05) but then remained stable in 2004 (40 [7.8 per 10,000]) and 2005 (44 [8.7 per 10,000]).
During a comparable time frame, the estimated prevalence of folic acid consumption in nonpregnant women 18 to 44 years of age increased significantly from 20.2% in 1997 to 30.9% in 2003, then decreased to 24.8% in 2006. Correspondingly, the estimated prevalence of knowledge of folic acid increased from 22.4% in 1997 to 72.0% in 2003 but then declined to 56.5% in 2006.
In 2006, women with more education and those with highest household incomes were more likely to have knowledge regarding folic acid and to consume a folic acid supplement daily.
"The end of the decline in NTD (i.e., spina bifida and anencephaly) prevalence in Puerto Rico in recent years is a cause for concern," an accompanying editorial notes. "The decline from 1996 to 2003 likely was aided by a campaign urging women to consume folic acid supplements and by introduction of mandatory folic acid fortification of U.S. cereal grain products in 1998. During a similar period, 1997–2003, reported folic acid supplement consumption and knowledge about folic acid increased among women in Puerto Rico, before declining from 2003 to 2006."
Limitations of these findings are that BRFSS survey participants include only noninstitutionalized persons with landline telephones, BRFSS questions regarding folic acid consumption do not specify the recommended daily dose and pertain only to vitamin supplements, possible failure to document all NTDs, and prevalence of NTDs, which are rare, might be affected by even slight variations in surveillance methods.
"The folic acid campaign in Puerto Rico continues," the editorialist writes, noting health fairs and other educational campaigns. "However, despite these measures, only approximately one fourth of women of childbearing age in Puerto Rico consume a vitamin containing folic acid daily, suggesting that other factors might affect behavior. Additional measures directed at understanding these factors and promoting folic acid awareness and consumption among all nonpregnant Puerto Rican women of childbearing age are warranted."
An accompanying QuickStats article describes rates of anencephaly and spina bifida in the United States in 1991, 1995, 2000, and 2005. Beginning in 1992, a US national health recommendation has mandated that women of childbearing age consume 400 μg of folic acid daily to decrease the risk of NTD should they become pregnant.
Decrease in the rate of spina bifida per 100,000 live births was 25% from 1995 to 2000 and 13% from 2000 to 2005. Although the rate of anencephaly decreased 36% from 1991 to 1995, it did not change significantly from 1995 to 2005.
MMWR Morb Mortal Wkly Rep. 2008;57(1):10–13, 15.