Maternal use of folic acid supplements during pregnancy and four-year-old neurodevelopment in a population-based birth cohort

The use of folic acid supplements during very early pregnancy is recommended in order to reduce the incidence of neural tube defects. Little is known about the possible benefits of folic acid on child neurodevelopment. A total of 420 children (87% of those eligible) from a birth cohort had complete data for final analyses at age 4 years. Information about folic acid and other over-the-counter dietary supplements was obtained prospectively using interviewer-administered questionnaires at the end of the first trimester of pregnancy. Psychological outcomes were assessed by two psychologists and teachers 4 years later.
Low maternal socio-economic status, smoking, high parity and short duration of breast feeding were associated with lower prevalence of folic acid supplement use. Verbal (b = 3.98, SE = 1.69), motor (b = 4.54, SE = 1.66) and verbal-executive function (b = 3.97, SE = 1.68) scores, social competence (b = 3.97, SE = 1.61) and inattention symptom [OR = 0.46; 95% CI 0.22, 0.95] scores were associated with reported folic acid use. Reported folic acid supplement use during pregnancy was associated with improved neurodevelopment in children after adjusting for a number of sociodemographic and behavioural factors.     

神经管畸形高、低发区农村孕早期妇女血液叶酸水平比较研究

目的 了解神经管畸形高发区与低发区农村孕早期妇女血液叶酸状况。方法 采用现况调查方法对2003年神经管畸形高发与低发两个地区共688名农村孕早期妇女的血浆叶酸与红细胞叶酸水平进行研究。结果 高发区农村孕早期妇女血浆叶酸浓度（10．53nmol／L）与红细胞叶酸浓度（389．2nmol／L）中位数明显低于低发区妇女（血浆叶酸30．39nmol/L，红细胞叶酸926．0nmol／L），差异有统计学意义；高发区妇女血浆叶酸缺乏率约为50％，红细胞叶酸缺乏率约为43％，远高于低发区妇女（血浆叶酸6％，红细胞叶酸4％），差异有统计学意义；高、低发区服用叶酸组妇女血浆叶酸水平约为不服用组的2倍，红细胞叶酸水平是不服用组的1．4倍，差异有统计学意义；高、低发区服用叶酸组孕早期妇女的血浆缺乏率均低于不服用组，相对危险度（RR）值分别为0．60（95％CI：0．36～1．01）与0．16（95％CI：0．06～0．44），差异均有统计学意义；高、低发区服用叶酸组与不服用组红细胞叶酸缺乏率之间的RR值分别为0．64（95％CI：0．36～1．13）与0．39（95％CI：0．13～1．13），差异无统计学意义；服用叶酸的孕早期妇女中，低发区血浆叶酸水平约为高发区的1．7～1．9倍，红细胞叶酸水平约为高发区的2倍，差异有统计学意义；服用叶酸的孕早期妇女中，高发区血浆叶酸与红细胞叶酸缺乏率约为低发区的10～14倍，差异有统计学意义。结论 神经管畸形高发区农村孕早期妇女血液叶酸水平很低，增补叶酸可有效提高妇女血液叶酸水平、降低妇女叶酸缺乏率，高发区育龄妇女怀孕前后每日服用0．4mg叶酸的剂量可能不足，建议增加服用剂量。     

Patterns and predictors of folic acid supplement use among pregnant women: the Norwegian Mother and Child Cohort Study

BACKGROUND: Patterns and predictors of maternal folic acid supplement use have not been examined in large prospective studies of pregnant women. OBJECTIVE: We examined the patterns and predictors of maternal folic acid supplement use from 2 mo before pregnancy through the eighth month of pregnancy. DESIGN: Data from 22 500 women in the Norwegian Mother and Child Cohort Study with deliveries recorded in 2000-2003 were analyzed. RESULTS: Folic acid supplement use increased from 11.8% at 2 mo before pregnancy to 46.9% at gestational month 3, but decreased to 26.0% at gestational month 8. Of 16 116 women (71.6%) who had taken folic acid supplements at some time before or during pregnancy, 72.4% had started use after becoming pregnant. Ten percent of the women had used supplements regularly from 1 mo before pregnancy throughout the first trimester. These women more frequently reported higher maternal and paternal education, planned pregnancies, infertility treatments, or chronic diseases. They were also more likely to be older, married, and nonsmokers and to have higher income and lower parity. CONCLUSIONS: Most women started folic acid supplementation too late with respect to the prevention of neural tube defects. More effective intervention programs to improve periconceptional intakes of folic acid are needed and should consider both demographic and socioeconomic factors.     

Epidemiology and (Patho)Physiology of Folic Acid Supplement Use in Obese Women before and during Pregnancy

Preconception folic acid supplement use is a well-known method of primary prevention of neural tube defects (NTDs). Obese women are at a higher risk for having a child with a NTD. As different international recommendations on folic acid supplement use for obese women before and during pregnancy exist, this narrative review provides an overview of epidemiology of folate deficiency in obese (pre)pregnant women, elaborates on potential mechanisms underlying folate deficiency, and discusses considerations for the usage of higher doses of folic acid supplements. Women with obesity more often suffer from an absolute folate deficiency, as they are less compliant to periconceptional folic acid supplement use recommendations. In addition, their dietary folate intake is limited due to an unbalanced diet (relative malnutrition). The association of obesity and NTDs also seems to be independent of folate intake, with studies suggesting an increased need of folate (relative deficiency) due to derangements involved in other pathways. The relative folate deficiency, as a result of an increased metabolic need for folate in obese women, can be due to: (1) low-grade chronic inflammation (2) insulin resistance, (3) inositol, and (4) dysbiotic gut microbiome, which plays a role in folate production and uptake. In all these pathways, the folate-dependent one-carbon metabolism is involved. In conclusion, scientific evidence of the involvement of several folate-related pathways implies to increase the recommended folic acid supplementation in obese women. However, the physiological uptake of synthetic folic acid is limited and side-effects of unmetabolized folic acid in mothers and offspring, in particular variations in epigenetic (re)programming with long-term health effects, cannot be excluded. Therefore, we emphasize on the urgent need for further research and preconception personalized counseling on folate status, lifestyle, and medical conditions.     

Effects of once-a-week or daily folic acid supplementation on red blood cell folate concentrations in women

OBJECTIVE: Our aim was to determine if a once-a-week folic acid supplement increases women's red blood cell folate to concentrations (>905 nmol/l) that are associated with a low risk of bearing a child with a neural tube defect. DESIGN: Randomized control trial. SETTING: General community. SUBJECTS: In total, 114 nonpregnant women (18-40 y) volunteers, with red blood cell folate concentrations between 295 and 905 nmol/l at screening. INTERVENTION: Women were randomized to receive a once-a-week 2800 microg folic acid supplement, a daily 400 microg folic acid supplement or a daily placebo for 12 weeks. RESULTS: The mean (95% CI) red blood cell folate concentrations increased during the 12-week intervention from 608 (553-668) to 900 (828-978) in the weekly folic acid group (P<0.05) and from 615 (560-677) to 1053 (957-1158) nmol/l in the daily group (P<0.05) during the trial. At week 12, 49% of women ingesting the weekly folic acid supplement had red blood cell folate concentrations greater than 905 nmol/l compared to 74% of women ingesting the daily supplement. CONCLUSION: A once-a-week 2800 microg folic acid supplement can increase women's red blood cell folate to concentrations associated with a reduced risk of bearing a child with a neural tube defect, but is less effective than a 400 microg daily supplement. Use of a weekly folic acid supplement over at least 12 weeks before conception by women of child-bearing age may prevent neural tube defects. FUNDING: The Otago Medical Research Foundation (Laurenson Award). Healtheries (New Zealand) provided the supplements.     

Assessment of the potential effect of incremental increases in folic acid intake on neural tube defects in Australia and New Zealand

OBJECTIVE: To estimate the number of neural tube defects that could be prevented in Australia and New Zealand by increasing levels of folic acid intake. METHODS: Available data on prevalence of neural tube defects in Australia and New Zealand, folic acid supplement use and serum folate were used in a published model to estimate the number of neural tube defects that could be prevented in Australia and New Zealand for increments of folic acid intake from 0.1 mg daily to 1 mg daily. RESULTS: An increase of 0.2 mg folic acid per day was estimated to result in the prevention of 49 (95% CI 27-84) neural tube defects per year in Australia and 11 (95% CI 6-18) in New Zealand. A separate estimation for Indigenous Australians found that 0.2 mg of folic acid daily could prevent 7 (95% CI 4-11) neural tube defects in Indigenous infants per year. CONCLUSIONS: These data should be useful in considering primary preventive strategies for neural tube defects, including the possible introduction of mandatory fortification of food with folic acid. The estimates are imprecise because of limitations in the data used in the model. IMPLICATIONS: More representative and precise data on neural tube defects, serum folate levels and use of folic acid supplements from all Australian States and New Zealand are needed to refine the output from the model and to provide a baseline assessment of folate status against which to measure the effects of any future interventions to prevent neural tube defects.     

Changes in knowledge and attitudes of folate, and use of dietary supplements among women of reproductive age in Norway 1998-2000

AIMS: From March 1998, Norwegian nutrition authorities have recommended that women consume a folic acid supplement before and early in pregnancy to prevent neural tube defects. The authors wished to establish Norwegian data on knowledge of, use of, and attitudes to folic acid supplement and dietary supplements before and after implementing national information campaigns on folate and pregnancy. METHODS: Telephone surveys were carried out in late 1998 and in late 2000 among, respectively, 1,146 and 1,218 Norwegian women of reproductive age. RESULTS: Overall, 50% of the women in 1998 and 60% of the women in 2000 had heard about folate, 33% and 46% knew about its role in pregnancy, and 9.5% and 21% knew that it may prevent a congenital malformation. Only 4.0% and 8.5% of the women, respectively, knew that the critical period for folic acid supplement to reduce the risk of neural tube defect is before and early in pregnancy. Knowledge and increase in knowledge between the two surveys were highest among women close to pregnancy (woman planning pregnancy, pregnant women, or women who had given birth within the last 12 months), and among women with high education. Among the 54 women in 1998 and the 55 women in 2000 whose last birth was within the previous year, use of a folic acid supplement before or early in the last pregnancy was reported by 10% (95% confidence interval (CI) 5-21%) and by 47% (95% CI 35-60%), respectively. Among women close to pregnancy, 76% in 1998 and 87% in 2000 stated that they would use a folic acid supplement in a future pregnancy. CONCLUSIONS: Knowledge and use of folate among Norwegian women increased from 1998 to 2000. Future information strategies on folate and pregnancy should in particular aim at increasing women's knowledge on the critical period for folic acid supplementation, as well as reducing socio-demographic differences in use and knowledge of folate.     

Prevalence and correlates of folic acid supplement use in Canada

Dietary supplements are an important source of folic acid, a nutrient that is vital in reducing the risk of neural tube defects. As part of the 2007 to 2009 Canadian Health Measures Survey, data were collected on supplement use, and biomarkers were directly measured. Use of supplements that contain folic acid was reported by 25% of Canadians aged 6 to 79. Females were more likely than males to report taking folic acid supplements. People who ate fruit and vegetables less than once a day had significantly lower odds of taking folic acid-containing supplements than did those who ate fruit and vegetables at least three times a day. Of those who consumed a folic acid supplement, 91% reported also taking a supplement that contained vitamin B12. Red blood cell folate concentrations below the median (less than 1,248 nmol/L), low-to-marginal serum vitamin B12 concentrations (221 pmol/L or less), and high concentrations of plasma homocysteine were negatively correlated with folic acid-containing supplement use.     

Neural tube defects and maternal folate intake among pregnancies conceived after folic acid fortification in the United States

Rates of neural tube defects have decreased since folic acid fortification of the food supply in the United States. The authors' objective was to evaluate the associations between neural tube defects and maternal folic acid intake among pregnancies conceived after fortification. This is a multicenter, case-control study that uses data from the National Birth Defects Prevention Study, 1998-2003. Logistic regression was used to compute crude and adjusted odds ratios between cases and controls assessing maternal periconceptional use of folic acid and intake of dietary folic acid. Among 180 anencephalic cases, 385 spina bifida cases, and 3, 963 controls, 21.1%, 25.2%, and 26.1%, respectively, reported periconceptional use of folic acid supplements. Periconceptional supplement use did not reduce the risk of having a pregnancy affected by a neural tube defect. Maternal intake of dietary folate was not significantly associated with neural tube defects. In this study conducted among pregnancies conceived after mandatory folic acid fortification, the authors found little evidence of an association between neural tube defects and maternal folic acid intake. A possible explanation is that folic acid fortification reduced the occurrence of folic acid-sensitive neural tube defects. Further investigation is warranted to possibly identify women who remain at increased risk of preventable neural tube defects.     

Continuing low uptake of periconceptional folate warrants increased food fortification

Objective To assess whether the Health Education Authority's recent promotion of periconceptional folic acid has been successful in increasing uptake sufficient to prevent neural tube defects.
Design A retrospective questionnaire, completed by 162 patients in the early pregnancy clinic in Doncaster Royal Infirmary, an average-sized UK district general hospital. The study ran in February and March 1999.
Methods and main outcome measures Data were collected on: supplementation and dietary intake of folic acid, both preconceptionally and after confirmation of pregnancy; awareness of the benefits of folic acid; source of information on folic acid; the reasons for not taking folic acid (if this was so); planned or unplanned pregnancy; previous pregnancies; previous neural tube defect in a pregnancy; smoking habit; and age.
Results Eighty-one per cent of women were aware of the benefits of folic acid, but only 27% took it preconceptionally. Sixty-eight per cent took it after confirmation of pregnancy. A quarter of patients made an attempt to increase dietary folate. Unplanned pregnancy was a significant bar to uptake, with significant differences in awareness and consumption. Number of pregnancies had no effect. Older women were more likely to take postconceptional folate, but awareness and preconceptional use were the same as younger women.
Conclusion Despite an extensive campaign commissioned by the Department of Health and run by the Health Education Authority, use of periconceptional folate will probably only prevent one-sixth of affected pregnancies. The adverse effects of fortification discussed in the body of this paper are small. It is now time for increased fortification of all cereal-grain products to be instituted in the UK in a similar manner to the United States.     

Folic Acid Use in Planned Pregnancy: An Italian Survey

It is well known that periconceptional folic acid supplementation decreases the risk of neural tube defects. The aim of this study was to evaluate the attitudes and practices of women with planned pregnancies regarding periconceptional folic acid intake and to identify factors associated with the use of this supplement. During 2 years of observation, we surveyed women with planned pregnancies who called our Teratology Information Service. A total of 500 women were surveyed: 217 (43.4 %) took folic acid before becoming pregnant, and 283 (56.6 %) did not take it. The women who took folic acid before becoming pregnant had a high education level and received preconception counselling. Our results suggest that less than half of Italian women took folic acid before they became pregnant although they were trying to conceive. Knowledge about the benefits of this vitamin is inadequate also among women who planned the pregnancy and the level of information received from their physicians.     

Dietary Intakes of Folate,Vitamin D and Iodine during the First Trimester of Pregnancy and the Association between Supplement Use and Demographic Characteristics amongst White Caucasian Women Living with Obesity in the UK

Folate, vitamin D and iodine are key micronutrients in pregnancy, with deficiency associated with poor maternal and infant outcomes. For folate and vitamin D especially, deficiency is more common amongst women with obesity and recommended intakes and guidance on supplementation varies worldwide. The present study aims to investigate dietary and supplementary intakes of these micronutrients amongst a population of pregnant women with obesity in the United Kingdom, alongside key maternal demographic characteristics. Expectant women (n = 75) with a body mass index ≥ 30 kg/m² at first antenatal appointment were recruited at 12 weeks gestation. Participants were asked about their supplement use preconception and during trimester one in a baseline questionnaire which also asked about demographic characteristics. Women also completed a four day diet diary from which dietary and supplemental intakes of micronutrients intakes were estimated. Folic acid was taken by 96% of women at any point in trimester 1, whilst only 26% of women took the higher 5 mg dose recommended for women with obesity in the UK. For vitamin D and iodine, 56% and 44% of women met the UK RNI, respectively. Maternal age was positively associated with taking supplements of any kind and the 5 mg folic acid supplement, whilst parity was inversely associated with both outcomes. This study strengthens the rationale for further work to be done raising awareness of the need for women with obesity to supplement both with a higher dose of folic acid and vitamin D and to be aware of the role of iodine during pregnancy.     

Trends in neural tube defects in Western Australia

OBJECTIVE: To report on trends in neural tube defects in Western Australia, in relation to folate promotion, periconceptional use of folic acid supplements and food fortification with folate. METHODS: Data on neural tube defects from the Western Australian Birth Defects Registry. RESULTS: A 30% fall in neural tube defects was documented from 1996 to 2000. CONCLUSIONS AND IMPLICATIONS: The sustained fall in neural tube defects is thought to be due to increased periconceptional folate intake in response to health promotion campaigns and fortification of selected foods. There is room for further improvement.     

Women Taking a Folic Acid Supplement in Countries with Mandatory Food Fortification Programs May Be Exceeding the Upper Tolerable Limit of Folic Acid: A Systematic Review

Background: In preconception and pregnancy, women are encouraged to take folic acid-based supplements over and above food intake. The upper tolerable limit of folic acid is 1000 mcg per day; however, this level was determined to avoid masking a vitamin B12 deficiency and not based on folic acid bioavailability and metabolism. This review’s aim is to assess the total all-source intake of folate in women of childbearing age and in pregnancy in high-income countries with folate food fortification programs. Methods: A systematic search was conducted in five databases to find studies published since 1998 that reported folate and folic acid intake in countries with a mandatory fortification policy. Results: Women of childbearing age do not receive sufficient folate intake from food sources alone even when consuming fortified food products; however, almost all women taking a folic acid-based supplement exceed the upper tolerable limit of folic acid intake. Conclusions: Folic acid supplement recommendations and the upper tolerable limit of 1000 mcg set by policy makers warrant careful review in light of potential adverse effects of exceeding the upper tolerable limit on folic acid absorption and metabolism, and subsequent impacts on women’s health during their childbearing years.     

Effect of time of initiation and dose of prenatal iron and folic acid supplementation on iron and folate nutriture of Korean women during pregnancy

BACKGROUND: In Korea, it is customary to prescribe iron and folic acid supplements to pregnant women after the 20th wk of gestation; however, little evidence exists to support this practice. OBJECTIVE: The objective was to determine the effects of time of initiation and dose of prenatal iron and folic acid supplementation on the iron and folate nutriture of Korean women during pregnancy. DESIGN: A total of 131 pregnant women were placed into 1 of 5 experimental groups, either the control group or 1 of 4 supplemented groups. The supplemented groups varied by time of initiation, which was either during the first trimester or at week 20 of gestation, and by dose of iron and folic acid supplements provided, which consisted of either 30 mg Fe plus 175 microg folic acid or 60 mg Fe plus 350 microg folic acid. All supplemented groups continued supplementation until delivery. RESULTS: Improvements in iron and folate nutriture were highly dependent on when the supplement program was initiated, but both supplement doses were equally effective. In contrast, the influence of folic acid supplementation on maternal folate status was not as pronounced as was the influence of iron supplementation on iron status. CONCLUSION: In pregnant Korean women, initiating iron and folic acid supplementation earlier during pregnancy may prevent the deterioration of iron and folate nutriture more than does increasing supplement doses in later stages of pregnancy.     

Folate Status of Young Canadian Women after Folic Acid Fortification of Grain Products

Women of childbearing age are advised to consume folic acid–containing supplements. Whether this remains necessary after folic acid fortification of the food supply in North America has yet to be determined. The objectives of this study were to assess folate intakes and the contribution of folic acid to the diets of women of childbearing age in the post–folic acid fortification era. Using a cross-sectional study design, fasting blood samples were obtained from 95 women (aged 18 to 25 years), and the samples were analyzed for serum and red blood cell folate, as well for total homocysteine. Dietary and supplemental folate intakes were assessed. The biochemical evidence showed that no women were folate deficient, but only 14% reached red blood cell folate concentrations associated with significant reductions in neural tube defect risk. Mean dietary intake of food folic acid was 96±64 μg/day, supplemental folic acid was 94±189 μg/day, natural folate was 314±134 μg/day, and the total intake, as dietary folate equivalents, was 646±368 μg dietary folate equivalents/day. Therefore, intakes of folic acid from fortified foods are within the level originally predicted for the fortification efforts; however, only 17% of participants met the special recommendation for women capable of becoming pregnant (400 μg folic acid daily from supplements, fortified foods, or both in addition to consuming food folate from a varied diet). These data suggest that women of childbearing age are achieving positive folate status in the postfortification era, but it may not be sufficient to achieve red blood cell folate concentrations associated with a significant reduction in neural tube defect risk. Even with food fortification, women of childbearing age should be advised to take a folic acid–containing supplement on a daily basis.     

出生缺陷高发区与低发区孕早期妇女叶酸知信行现况比较

目的了解出生缺陷高发区与低发区孕早期妇女叶酸知信行状况.方法采用横断面调查与对比研究，对出生缺陷高发与低发4个地区共1554名孕早期妇女的叶酸知识的了解情况、服用叶酸增补剂的态度及叶酸增补剂服用情况进行了问卷调查。结果出生缺陷高发区孕早期妇女听说过叶酸的比例(农村22．7％、城市60．7％)、知道叶酸预防神经管畸形作用的比例(农村18．1％、城市51．5％)，低于出生缺陷低发区妇女(农村85．1％、城市85．6％；农村、城市76．1％)；对于叶酸增补剂最佳服用时期，高发区农村孕早期妇女知晓率为16．3％、城市为35．9％，低于出生缺陷低发区(农村68．2％、城市68．8％)；出生缺陷高发区妇女认为有必要服用叶酸增补剂的比例(农村20．4％、城市50．7％)远低于出生缺陷低发区(农村76．1％、城市79．7％)；出生缺陷高发区城市与农村妇女叶酸增补剂服用率仅为8．5％和31．1％，低于出生缺陷低发区(农村63．4％、城市67．5％)。结论出生缺陷高发区孕早期妇女叶酸知识缺乏，叶酸增补剂服用率低。应通过健康教育和宣传，提高出生缺陷高发区育龄妇女对叶酸的认识和增补率。     

新《婚姻登记条例》实施前后孕早期妇女叶酸知识和增补率的变化

目的:了解新《婚姻登记条例》实施前后孕早期妇女叶酸知信行变化状况。方法:采用横断面调查与对比研究,对无锡市新《婚姻登记条例》实施前登记结婚的75例和实施后52例孕早期妇女的叶酸知识的了解情况、服用叶酸增补剂的态度及叶酸增补剂服用情况进行了问卷调查。结果:实施后组孕早期妇女对于叶酸增补剂最佳服用时期的知晓率为42.31%,低于实施前的66.67%(P<0.01);实施后组妇女叶酸增补剂服用率为44.23%,低于实施前的62.67%(P<0.05);实施后组从卫生保健机构获得叶酸知识的构成比例为28.95%,低于实施前的82.76%(P<0.01);实施后组孕早期妇女听说过叶酸的比例(73.08%)、知道叶酸预防神经管畸形作用的比例(55.77%)和有必要服用叶酸增补剂的比例(65.38%),均低于实施前组妇女(分别为77.33%、66.67%和73.33%),但差别无统计学意义。结论:新《婚姻登记条例》实施后,无锡市孕早期妇女叶酸相关知识、叶酸增补剂服用率呈现下降趋势。应积极探索新的知识传播途径,增加育龄妇女的叶酸知识,提高叶酸增补剂服用率。     

Consumption of Cereal Flour in a Malaysian Population: Flour Fortification to Prevent Neural Tube Defect May Be Feasible in a Rice-Eating Country

To assess the feasibility of fortifying flour with folic acid as a strategy to prevent neural tube defects in Malaysia, a country where the staple food is rice, we used 24-hour recall to study all cereal flour intake in women of reproductive age. Eighty-eight percent took at least a half portion of cereal flour and 85% took at least one whole portion. Vitamin supplements were taken by 36% but few knew whether the supplement contained folic acid. Cereal flour consumption is frequent and folic acid fortification of flour is feasible. Subgroups of the population not consuming flour need to be identified.     

无锡地区早期妊娠妇女血液叶酸浓度季节变化趋势及影响因素

目的了解无锡地区早期妊娠妇女血液叶酸浓度,观察血液叶酸浓度随季节变动趋势,分析血液叶酸浓度的影响因素。方法研究对象为孕12周内妇女。采用面对面调查方法收集资料,每名妇女采集非空腹静脉血4ml测定血浆叶酸和红细胞叶酸浓度。采用逐步回归方法筛选血液叶酸浓度的影响因素。采用协方差分析,计算调整相关混杂因素后不同季节以及服用和不服用叶酸增补剂者的血液叶酸浓度。结果2002年12月至2003年11月共募集早期妊娠妇女596名。血浆叶酸和红细胞叶酸浓度的几何均数分别为34．1 nmol／L和902．8 nmol／L,缺乏率分别为3．0％和2．4％。但50％早期妊娠妇女的红细胞叶酸浓度低于预防神经管畸形的最佳水平(906 nmol／L)。血浆叶酸浓度4～6月最低;红细胞叶酸浓度1-3月最低。围受孕期服用叶酸增补剂可以显著提高血浆叶酸浓度和红细胞叶酸浓度;血浆叶酸浓度和红细胞叶酸浓度随妇女年龄增加而升高;农村早期妊娠妇女的血浆叶酸浓度低于城市早期妊娠妇女;每日食用1次及以上水果者的红细胞叶酸浓度高于水果食用频率不足每日1次者。对年龄和居住地调整后,围受孕期服用叶酸增补剂妇女的血浆叶酸浓度比未服用者高1倍以上(P<0．001);对年龄和食用水果频率调整后,服用叶酸增补剂妇女的红细胞叶酸浓度比未服用者高42％(P<0．001)。结论无锡地区早期妊娠妇女叶酸缺乏率不高,但有50％早期妊娠妇女的红细胞叶酸浓度低于预防胎儿神经管畸形的最佳水平。红细胞叶酸浓度1—3月处于低谷,此时受孕,胎儿神经管畸形的危险性将增加。围受孕期服用叶酸增补剂可显著提高血液叶酸浓度。在制订育龄妇女增补叶酸计划时,应结合改变膳食教育,并应重点关注农村妇女。