Prevention of neural-tube defects with folic acid in China. China-U.S. Collaborative Project for Neural Tube Defect Prevention

Preconception homocysteine and B vitamin status and birth outcomes in Chinese women

BACKGROUND

The associations between homocysteine, B vitamin status, and pregnancy outcomes have not been examined prospectively.

OBJECTIVE

We assessed the associations of preconception homocysteine and B vitamin status with preterm birth and birth of low-birth-weight (LBW) and small-for-gestational-age (SGA) infants in Chinese women.

DESIGN

This was a case-control study of women aged 21-34 y. Preterm cases (n = 29) delivered living infants at <37 wk gestation; term controls (n = 405) delivered infants at > or =37 wk. LBW cases (n = 33) had infants weighing <2500 g; normal-birth-weight controls (n = 390) had infants weighing > or =2500 g. SGA cases (n = 65) had infants below the 10th percentile of weight-for-gestational-age; appropriate-for-gestational-age controls (n = 358) had infants above this cutoff. Nonfasting plasma concentrations of homocysteine, folate, and vitamins B-6 and B-12 were measured before conception.

RESULTS

Elevated homocysteine (> or =12.4 micro mol/L) was associated with a nearly 4-fold higher risk of preterm birth (OR: 3.6; 95% CI: 1.3, 10.0; P < 0.05). The risk of preterm birth was 60% lower among women with vitamin B-12 > or =258 pmol/L than among vitamin B-12-deficient women (OR: 0.4; 95% CI: 0.2, 0.9; P < 0.05) and was 50% lower among women with vitamin B-6 > or =30 nmol/L than among vitamin B-6-deficient women (OR: 0.5; 95% CI: 0.2, 1.2; NS). Folate status was not associated with preterm birth, and homocysteine and B vitamin status were not associated with LBW or SGA status.

CONCLUSIONS

Elevated homocysteine and suboptimal vitamin B-12 and B-6 status may increase the risk of preterm birth. These results need to be confirmed in larger prospective studies.

Genetic effects of methylation diets

DNA methylation at cytosines in CpG dinucleotides can lead to changes in gene expression and function without altering the primary sequence of the DNA. Methylation can be affected by dietary levels of methyl-donor components, such as folic acid. This may be an important mechanism for environmentally induced changes in gene expression. Recent literature supports a role for DNA-methylation changes in a number of adult-onset disorders and during development. These changes may be significant for better understanding certain birth defects (e.g., neural tube defects) and the long-term consequences of early environmental influences on gene expression (metabolic programming). Optimal "methylation diets" should be investigated as part of the prevention and treatment of all these conditions, as well as in disorders such as Rett syndrome, whose primary defects may lie in DNA methylation-dependent gene regulation.

Decline of neural tube defects cases after a folic acid campaign in Nuevo León, México

BACKGROUND

Nuevo León is a state in northeastern Mexico, near the border of Texas. Mean mortality rate from 1996-98 due to anencephaly cases was 0.6/1,000. In 1999 a surveillance program for the registry and prevention of neural tube defects (NTD) cases was initiated.

METHODS

Cases were obtained from hospitals and OB-GYN clinics by immediate notification, death certificates, or fetal death registries. Only isolated cases of NTD were included. In August 1999 a folic acid campaign was initiated with the free distribution of the vitamin to low-income women with a recommendation to take a 5.0-mg pill once a week. Number of cases and rates from 1999 to 2001 were compared (chi(2) test).

RESULTS

After 2 years there has been a significant reduction in the number of cases and rates. In 1999 there were 95 NTD cases and in the years 2000 and 2001 there were only 59 and 55 respectively (P < 0.001). NTD rate decreased from 1.04/1,000 in 1999 to 0.58/1,000 in 2001. Anencephaly and spina bifida rates decreased from 0.55/1,000 to 0.29/1,000 and from 0.47/1,000 to 0.22/1,000 respectively, from 1999-2001. Decrease of female cases was higher than male cases for both phenotypes.

CONCLUSION

After 2 years there was a 50% decrease in the incidence of anencephaly and spina bifida cases with a significant reduction of infant mortality and disability. These results encourage us to propose the use of a single tablet of 5.0-mg of folic acid per week as an alternative to supplementation on a daily basis.

The human reduced folate carrier gene is ubiquitously and differentially expressed in normal human tissues: identification of seven non-coding exons and characterization of a novel promoter

Our previous study identified two alternate non-coding upstream exons (A and B) in the human reduced folate carrier (hRFC) gene, each controlled by a separate promoter. Each minimal promoter was regulated by unique cis -elements and transcription factors, including stimulating protein (Sp) 1 and Sp3 and the basic leucine zipper family of proteins, suggesting opportunities for cell- and tissue-specific regulation. Studies were performed to explore the expression patterns of hRFC in human tissues and cell lines. Levels of hRFC transcripts were measured on a multi-tissue mRNA array from 76 human tissues and tumour cell lines and on a multi-tissue Northern blot of representative tissues, each probed with full-length hRFC cDNA. hRFC transcripts were ubiquitously expressed, with the highest level in placenta and the lowest level in skeletal muscle. By rapid amplification of cDNA 5'-ends assay from nine tissues and two cell lines, hRFC transcripts containing both A and B 5'-untranslated regions (UTRs) were identified. However, five additional 5'-UTRs (designated A1, A2, C, D and E) were detected, mapping over 35 kb upstream from the hRFC translation start site. The 5'-UTRs were characterized by multiple transcription start sites and/or alternative splice forms. At least 18 unique hRFC transcripts were detected. A novel promoter was localized to a 453 bp fragment, including 442 upstream of exon C and 11 bp of exon C. A 346 bp repressor flanked the 3'-end of this promoter. Our results suggest an intricate regulation of hRFC gene expression involving multiple promoters and non-coding exons. Moreover, they provide a transcriptional framework for understanding the role of hRFC in the pathophysiology of folate deficiency and antifolate drug selectivity.

The epidemiology of developmental disabilities in low-income countries

Although most of the world's children live in developing countries and may be at high risk for disability, very little is known about the prevalence and causes of developmental disabilities in these countries. This paper discusses methodological difficulties contributing to this lack of knowledge, and provides an overview of what is known about the epidemiology of developmental disabilities in low-income countries. At least some forms of developmental disability appear to be more common in low-income countries than in wealthier countries, despite the probability of higher mortality among children with disabilities in low-income countries. For example, most studies of severe mental retardation in low-income countries report prevalences greater than 5 per 1,000 children, while prevalence estimates from industrialized countries are consistently below this. Major risk factors for developmental disabilities in some low-income countries include specific genetic diseases, a higher frequency of births to older mothers, consanguinity, and specific micronutrient deficiencies and infections. Trauma and toxic exposures are also important risk factors, but their contributions to the etiology of developmental disabilities in low-income countries are not well documented. Though many of the causes of developmental disabilities are understood and preventable, proven methods of prevention are not being fully implemented in developing countries. Epidemiologic studies are needed to raise awareness of the public health impacts of developmental disabilities in low-income countries and to provide a basis for setting priorities and designing efficient interventions.

Position of the American Dietetic Association: nutrition and lifestyle for a healthy pregnancy outcome

It is the position of the American Dietetic Association that women of childbearing potential should maintain good nutritional status through a lifestyle that optimizes maternal health and reduces the risk of birth defects, suboptimal fetal growth and development, and chronic health problems in their children. The key components of a health-promoting lifestyle during pregnancy include appropriate weight gain; consumption of a variety of foods in accordance with the Food Guide Pyramid; appropriate and timely vitamin and mineral supplementation; avoidance of alcohol, tobacco, and other harmful substances; and safe food-handling. Prenatal weight gain within the Institute of Medicine (IOM) recommended ranges is associated with better pregnancy outcomes. The total energy needs during pregnancy range between 2,500 to 2,700 kcal a day for most women, but prepregnancy body mass index, rate of weight gain, maternal age, and physiological appetite must be considered in tailoring this recommendation to the individual. The consumption of more food to meet energy needs and the increased absorption and efficiency of nutrient utilization that occurs in pregnancy are generally adequate to meet the needs for most nutrients. However, vitamin and mineral supplementation is appropriate for some nutrients and situations. This statement also includes recommendations pertaining to use of alcohol, tobacco, caffeine, street drugs, and other substances during pregnancy; food safety; and management of common complaints during pregnancy and specific health problems. In particular for medical nutrition therapy, pregnant women with inappropriate weight gain, hyperemesis, poor dietary patterns, phenylketonuria (PKU), certain chronic health problems, or a history of substance abuse should be referred to a qualified dietetics professional.

Dietary counseling to increase natural folate intake: a randomized, placebo-controlled trial in free-living subjects to assess effects on serum folate and plasma total homocysteine

BACKGROUND

The association between vascular disease and elevated plasma total homocysteine (tHcy) concentrations is caused, in part, by inadequate intakes of dietary folate. Increasing folate intake either through supplements or foods naturally rich in folates has been shown to decrease tHcy concentrations.

OBJECTIVE

The aim of this study was to determine whether a similar reduction in tHcy was possible in free-living persons receiving dietary counseling.

DESIGN

The study included a 4-wk placebo-controlled dietary intervention trial in which participants consumed either unfortified breakfast cereal (control group) or an extra 350 micro g folate derived from food/d (dietary group). Serum folate and tHcy concentrations in both groups were measured before and after the intervention period, and the concentrations in the dietary group were also measured 17 wk after the intervention period.

RESULTS

During the 4-wk intervention, mean dietary folate intake in the dietary group increased from 263 (95% CI: 225, 307) to 618 micro g/d (535, 714), resulting in a mean increase in serum folate of 37% (15%, 63%) and a decrease in tHcy from 12.0 (10.9, 13.3) to 11.3 micro mol/L (10.2, 12.5). A further decrease in tHcy occurred in the dietary group during follow-up, with a final tHcy concentration of 9.7 micro mol/L (8.8, 10.8).

CONCLUSIONS

Increasing natural folate intake improved folate status and decreased tHcy concentrations to an extent that may significantly reduce the risk of vascular disease. Dietary modification may have advantages over folic acid fortification because the altered food-consumption patterns lead to increased intakes of several vitamins and minerals and decreased intakes of saturated fatty acids.

Prevention of fumonisin B1-induced neural tube defects by folic acid

BACKGROUND

The mycotoxin fumonisin B1 (FB1) inhibits sphingolipid synthesis, blocks folate transport, and has been associated with increased incidences of cancer and neural tube defects. Results from reproductive studies in animal models in vivo and in vitro have demonstrated toxicity in some cases, but no specific terata after fumonisin exposure. No information is available about folic acid's potential to protect against this toxicity.

METHODS

Neurulating mouse embryos were exposed to fumonisin or folinic acid in whole embryo culture and assessed for effects on growth and development.

RESULTS

Fumonisin exposure inhibited sphingolipid synthesis, reduced growth, and caused cranial neural tube defects in a dose dependent manner. Supplemental folinic acid ameliorated the effects on growth and development, but not inhibition of sphingolipid synthesis.

CONCLUSION

Fumonisin has the potential to inhibit embryonic sphingolipid synthesis and to produce embryotoxicity and neural tube defects. Folic acid can reverse some of these effects, supporting results showing that fumonisin disrupts folate receptor function.

Folic acid supplementation use among women who contact a teratology information service

OBJECTIVE

The purpose of this study was to determine the percentage of the women who call a teratology information service who take folic acid before conception.

STUDY DESIGN

A pilot-tested questionnaire was used to survey women who called a teratology information service about their use of folic acid supplementation. Frequencies were generated by pregnancy status, age, race, and parity.

RESULTS

Of the 693 pregnant callers, 42% of the women initiated folic acid use 6 weeks before pregnancy, 35% of the women initiated folic acid use during pregnancy. Thirty-seven percent of the total caller population reported taking folic acid. Forty-seven percent of pregnant white women versus 27% of pregnant black women reported preconceptional folic acid use (P =.005). Thirty-nine percent of pregnant women who were <30 years old reported preconceptional folic acid use versus 48% of women who were >30 years old (P =.018).

CONCLUSION

Most pregnant women take folic acid; however, only a minority of them start before conception. The use of preconceptional folic acid, although higher than the national average of 30%, was still low. Many women start taking folic acid in their pregnancy after the neural tube is closed.

Physical activity and risk of neural tube defects

OBJECTIVE

Owing to its association with known risk factors for neural tube defects (NTDs) and its impact on physiologic processes relevant to fetal development, physical activity was identified as a potential risk factor for NTD-affected pregnancy.

METHODS

Using data from a population-based case-control study of deliveries occurring in California from 1989 to 1991, we estimated the potential risk of having an NTD-affected pregnancy associated with variation in maternal physical activity. In-person interviews were conducted with 538 (88% of eligible) mothers of NTD cases and with mothers of 539 (88%) nonmalformed controls on average 5 months from the term delivery date. An index reflecting reported frequency and exertion level for six activity groups (e.g., jogging and running) was used to summarize each woman's physical activity level in the periconceptional period.

RESULTS

Unadjusted analyses indicated that compared to women considered inactive by this index, physically active women had 30-50% lower risk for NTD-affected pregnancies. After adjustment for several potential confounders and an evaluation of potential effect modification, results suggested that the association was restricted to women who did not take multivitamin/mineral supplements during the periconceptional period. Excluding mothers with reported medical problems did not substantially alter findings.

CONCLUSIONS

This study suggests that the benefits of physical activity may extend to reduction of NTD risk among certain subgroups of women.

Folic acid supplementation and prevention of birth defects

Based on animal studies, epidemiologic studies and intervention trials, maternal folic acid is known to be protective for neural tube defects (NTD), primarily spina bifida and anencephalus. To reduce the risk of NTD, the U.S. Food and Drug Administration mandated that all enriched cereal grain products be fortified with folic acid as of January 1998. Recent data demonstrate that this public health action is associated with increased folate blood levels among U.S. women of childbearing age and that the national rate of spina bifida has decreased by 20%. Rates of anencephaly appear not to have declined. Epidemiologic data on use of folate and folate antagonists have also implicated folic acid in prevention of other birth defects such as facial clefts and cardiac and limb defects. Dietary folic acid is likely to be inadequate for maximal protection against NTD. Because about half of pregnancies in the U.S. are unplanned, according to the March of Dimes, birth defect prevention includes a recommended daily dose of 400 micro g synthetic folic acid for women of childbearing age. Uniform compliance is estimated to decrease the incidence of NTD by up to 70%. This could reduce the overall incidence from 2 to 0.6 per 1000 pregnancies and prevent disease in approximately 2000 babies per year in the U.S. Four thousand micrograms of folic acid per day is recommended for women with previous pregnancies affected by NTD.

Trends in neural tube defect prevalence, folic acid fortification, and vitamin supplement use

In this review, the authors analyze international trends in rates of neural tube defects (NTDs) during the past three decades. Population-based data sources include the Metropolitan Atlanta Congenital Defects Program and other US birth defects surveillance programs in the National Birth Defects Prevention Network, the International Clearinghouse for Birth Defects Monitoring Systems, and US and Canadian vital records. To analyze trends in vitamin consumption, we review data from the US National Health and Nutrition Examination Surveys and international surveys of multivitamin use. We discuss the role of factors associated with historic and continuing declines in NTD rates in most countries. These factors include the introduction and increased utilization of prenatal diagnosis, recommendations for multivitamin use in women of childbearing age, and population-wide increases in blood folate levels that have occurred since food fortification was mandated. We also discuss research needs for further NTD prevention. This is a US government work. There are no restrictions on its use.

Use of folic acid and delivery outcome: a prospective registry study

Periconceptional use of folic acid is thought to reduce the risk for both neural tube defects and other congenital malformations. Most published data were obtained retrospectively. We used the Swedish Medical Birth Registry to study congenital malformations in infants born of women who reported the use of folic acid in early pregnancy (of which 70% probably used it also preconceptionally) and compared them with population rates. We divided the material according to two major confounders: subfertility problems and use of antiepileptic drugs. We found no protective effect of folic acid tablet use on the rate of congenital malformations but data on neural tube defects were scarce. Our results support the scepticism recently expressed in the literature on the beneficial effect of folic acid in preventing congenital malformations, especially of a non-neural tube defect type.

Spina bifida and folate-related genes: a study of gene-gene interactions

PURPOSE

To assess whether interactions of common alleles of two folate genes contribute to spina bifida risk.

METHODS

Case-control study, comparing 203 children with spina bifida to 583 controls.

RESULTS

Homozygosity for the 677C-T allele of 5,10-methylenetetrahydrofolate reductase (MTHFR) alone was associated with an odds ratio for spina bifida of 1.57 (95% confidence interval [CI], 1.02-2.38). For the 844ins68 allele of cystathionine-beta-synthase alone, the odds ratio was 0.83 (95% CI, 0.39-1.64). For the joint genotype, the odds ratio was 3.69 (95% CI, 1.04-13.50).

CONCLUSIONS

Interactions between common alleles of folate genes might contribute to the risk for spina bifida.

Investigation of the effects of folate deficiency on embryonic development through the establishment of a folate deficient mouse model

BACKGROUND

Folic acid (FA) has been shown to reduce the incidence of neural tube, craniofacial, and cardiovascular defects and low birth weight. The mechanism(s) by which the vitamin is effective, however, has not been determined. Therefore, a folic acid deficient mouse model was developed.

METHODS

To create a folic acid deficiency, ICR female mice were placed on a diet containing no FA and including 1% succinyl sulfathiazole (SS) for 4 weeks before mating. Control mice were fed diets with either: 1) FA and 1% SS [+SS only diet]; 2) FA [normal diet]; or 3) a breeding diet. Dams and fetuses were examined during various days of gestation.

RESULTS

Blood analysis showed that by gestational day 18, plasma folate concentrations in the -FA+SS fed dams decreased to 1.13 ng/ml, a concentration approximately 3% of that in breeding diet fed dams (33.24 ng/ml) and 8% of that in +SS only/normal fed dams (13.59 ng/ml). RBC folate levels showed a similar decrease, whereas homocysteine concentrations increased. Reproductive outcome in the -FA+SS fed dams was poor with increased fetal deaths, decreased fetal weight, and delays in palate and heart development.

CONCLUSIONS

Female mice fed a folic acid deficient diet and 1% succinyl sulfathiazole exhibited many of the characteristics common to human folic acid deficiency, including decreased plasma and RBC folate, increased plasma homocysteine, and poor reproductive outcomes. Thus, an excellent model has been created to investigate the mechanism(s) underlying the origin of birth defects related to folic acid deficiency.

Preconception care by the nonobstetrical provider

Clinicians who provide health care to women during their childbearing years have the opportunity to affect pregnancy outcomes positively through preconception care. The goal of preconception care is to identify medical and social conditions that may put the mother or fetus at risk. Key elements include screening for certain infectious diseases, obtaining genetic history, updating immunizations, providing specific nutritional advice, and optimizing health status. Some women, and their partners, may require additional care, including a prepregnancy consultation with an obstetrician or maternal-fetal medicine specialist. The clinician can also offer advice that may enhance conception and encourage either early prenatal care when a pregnancy is achieved or early evaluation for infertility.

Occurrence of omphalocele in relation to maternal multivitamin use: a population-based study

OBJECTIVE

We evaluated the association between mothers' use of multivitamin supplements and their infants' risk for omphalocele, a congenital anomaly of the abdominal wall. Omphalocele can occur in certain multiple congenital anomaly patterns with neural tube defects, for which a protective effect of multivitamins with folic acid has been demonstrated.

METHODS

We used data from a population-based case-control study of infants born from 1968-1980 to mothers residing in metropolitan Atlanta. Case-infants with nonsyndromic omphalocele (n = 72) were actively ascertained from multiple sources. Control-infants (n = 3029), without birth defects, were selected from birth certificates by stratified random sampling.

RESULTS

Compared with no use in the periconceptional period, periconceptional use of multivitamin supplements (regular use from 3 months before pregnancy through the first trimester of pregnancy) was associated with an odds ratio for nonsyndromic omphalocele of 0.4 (95% confidence interval [CI]: 0.2-1.0). For the subset comprising omphalocele alone or with selected midline defects (neural tube defects, hypospadias, and bladder/cloacal exstrophy), the odds ratio was 0.3 (95% CI: 0.1-0.9). These estimates were similar when the reference group also included women who began using multivitamins late in pregnancy (during the second or third month of pregnancy). The small number of participants limited the precision of subgroup analyses and translated into wide confidence intervals that included unity.

CONCLUSIONS

Periconceptional multivitamin use was associated with a 60% reduction in the risk for nonsyndromic omphalocele. These findings await replication from additional studies to confirm the findings, generate more precise estimates, and detail possible mechanisms of actions.

Dietary intake and blood folate levels in Honduran women of childbearing age

Neural tube defects are common birth defects, the frequency of which appears to be reduced by maternal supplementation and/or fortification of folic acid. Latin Americans have a high incidence of neural tube defects. We surveyed the dietary intake of Honduran women of childbearing age using a 24-hour dietary recall questionnaire in inner-city, town, and country areas. We randomly checked blood folate in the surveyed population to compare to the normal range for the US population. Normal US recommended dietary allowance intake of folate was documented in association with a low intake of many other essential nutrients. There also were significant differences for nutrient intakes in city, town, and country areas. Blood folate levels in all locations were in the low normal range when compared to the presupplementation/prefortification US population. Our data support using an established folic acid fortification public health initiative to decrease the prevalence of neural tube defects in Honduras.

Evaluation of the significance of dietary folate from wild vegetables in Vietnam

Data on the overall dietary folate intakes among high-risk groups in poor countries is very limited. Vegetables are considered good sources but the evaluation of their contribution is hampered by the lack of data on folate concentrations in many traditional foods. Data on the analysis of folate concentrations in 16 wild vegetables used in the Mekong Delta and the Central Highlands in Vietnam and an evaluation of the relative importance of different foods in folate intakes of women is presented. Vegetable samples were collected in four study villages, blanched and frozen samples were transported to Sweden for analysis. Freeze-dried samples were analysed for total folate quantification using a commercial radio protein binding assay. Daily folate intakes among women were estimated from 7-day food frequency interviews with 213 women. The folate concentration in the vegetable samples ranged from 10 to 96 microg/100 g. The mean estimated daily folate intake among the 213 women in the study areas was 251 microg. Vegetables contributed approximately one-third of the daily folate intake, of which 72% and 42%, respectively, in the two regions was from wild vegetables. A majority of the women (87%) got some dietary folate from wild vegetables and nearly one-third had mean daily folate intakes of > 50 microg from such hidden food sources. The evaluation of dietary folate is complicated by data gaps in food composition tables, the unreliability of existing food data, variations between methods used for folate analysis and limited understanding of the bioavailability of food folate.

Global Prevention of All Folic Acid-Preventable Spina bifida and Anencephaly by 2010

Folic acid-preventable spina bifida and anencephaly are pandemic, affecting 225,000 children a year. These birth defects are as preventable as polio. As we near the eradication of polio, it is time to make the commitment to global prevention of all folic acid-preventable spina bifida and anencephaly (FA-P SBA) by 2010. Folic acid fortification of centrally processed foods, such as wheat and corn flour, could immediately prevent all of these birth defects for much of the world's population. These fortification programs will also help adults by increasing serum folate concentration, eradicating folate deficiency anemia, providing human genome stability and reducing homocysteine serum concentration, which will probably prevent heart attacks and strokes, and may prevent colon cancer and Alzheimer's disease. Where there is no centrally processed and distributed food to fortify, intense efforts must be made to increase consumption of synthetic folic acid through vitamin supplements. Geneticists can play a major role in preventing FA-P SBA by helping to create the political will in each country to implement fortification and supplement programs to eliminate disease caused by the current pandemic of folate deficiency.

Fetal pharmacotherapy

Rapid progress has recently been encountered in pharmacologically treating the unborn baby. This unique area of drug therapy raises new methodological and ethical questions. This article is a systematic review of known modalities of fetal pharmacotherapy, and aims to highlight essential principles, difficulties and controversies in fetal pharmacotherapy. Unique pharmacokinetic features of pregnancy, the placenta and the fetus govern maternal-to-fetal drug transfer. Ethically, it is important that the mother and family are appropriately informed about the evidence in favour of specific fetal therapy, its risks and alternatives. Antenatal use of corticosteroids for lung maturation is an example of adequate methodology, leading to clear results. In contrast, the initial hopes in antenatal use of phenobarbital were based on less than optimal methodology. Folic acid for the prevention of neural tube defects is the first instance of fetal therapy that has led to the prevention of a major malformation. Serious infections, such as HIV, Group B streptococcus and toxoplasmosis highlight the need for controlled, randomised studies to prevent fetal infection. With scores of new modalities of fetal therapy likely to be introduced in the next few years, it will be important to adhere to the best possible methodology and execution, in order to address optimally the needs of the fetus.

Quantifying the effect of folic acid

BACKGROUND

Folic acid is known to prevent neural-tube defects (NTDs) but the size of the effect for a given dose is unclear. We aimed to quantify such an effect.

METHODS

We used published data from 13 studies of folic acid supplementation on serum folate concentrations and results from a large cohort study of the risk of NTDs according to serum folate, to measure the preventive effect of specified increases in intake of folic acid.

FINDINGS

Serum folate concentrations increase by 0.94 ng/mL (95% CI 0.77-1.10) for every 0.1 mg/day increase in folic acid intake in women aged 20-35 years, and about double that in people aged 40-65. Every doubling of serum folate concentration roughly halves the risk of an NTD. These two effects can be combined to predict the reduction in risk according to intake of extra folic acid and background serum folate concentration. Such results predict that the preventive effect is greater in women with low serum folate than in those with higher concentrations. The results have also been used to predict direct observations from large randomised trials and the effect of food fortification. From a typical western background serum folate of 5 ng/mL, about 0.2 mg/day (the US level of folic acid fortification) would be expected to reduce NTDs by about 20%; a similar effect can be expected from the current British recommendation (0.24 mg/day). An increase of 0.4 mg/day would reduce risk by about 36%, of 1 mg/day by 57%, and taking a 5-mg tablet daily would reduce risk by about 85%.

INTERPRETATION

Folic acid fortification levels should be increased. Additionally women planning a pregnancy should take 5 mg folic acid tablets daily, instead of the 0.4 mg dose presently recommended.

The teratogenic risk of trimethoprim-sulfonamides: a population based case-control study

OBJECTIVE

To study human teratogenic potential of two trimethoprim-sulfonamide combinations: trimethoprim-sulfamethoxazole (cotrimoxazole) and trimethoprim-sulfamethazine during pregnancy. These agents have antifolate effects and other antifolate agents can induce multiple congenital abnormalities, neural-tube defects, cardiovascular, and other malformations in animal experiments and in humans.

DESIGN

Pair analysis of cases with congenital abnormalities and matched healthy controls in the large population-based data set of the Hungarian Case-Control Surveillance of Congenital Abnormalities between 1980 and 1996.

PARTICIPANTS

38,151 pregnant women who had newborn infants without any congenital abnormalities (control group) and 22,865 case pregnant women who had newborns or fetuses with congenital abnormalities.

MAIN OUTCOME

Prevalence of drug use in matched case-control pairs to study the possible association with congenital abnormalities.

RESULTS

In the case group 351 (1.5%) and in the control group 443 (1.2%) pregnant women were treated with cotrimoxazole (crude OR 1.3 with 95% CI 1.1-1.5). In addition 45 (0.2%) case and 39 (0.1%) control pregnant women had trimethoprim-sulfamethazine treatment (crude OR 1.9 with 95% CI 1.3-3.0). A higher rate of multiple congenital abnormalities (including mainly urinary tract and cardiovascular abnormalities) was found in case infants born to mothers with cotrimoxazole treatment during the second-third months of pregnancy. In addition, a higher rate of cardiovascular malformations occurred in cases born to mothers with cotrimoxazole treatment and trimethoprim-sulfamethazine treatment during the second-third months of pregnancy, respectively.

CONCLUSION

Treatment with cotrimoxazole during pregnancy may increase the risk of cardiovascular malformations, and particularly multiple congenital abnormalities including defects of the urinary tract and cardiovascular system. A higher rate of cardiovascular malformations was also found after treatment with trimethoprim-sulfamethazine in the second-third months of pregnancy.

Micronutrients in women's health and immune function

Lawrence J. Machlin's contributions to elucidating the roles of nutrients in optimizing human health included the support of research in the areas of women's health and immune function. Several essential nutrients have been shown to affect women's health throughout the different life stages. Symptoms of premenstrual syndrome affect the vast majority of menstruating women, and calcium supplementation significantly reduces physical and emotional symptoms. Premenstrual syndrome in fact might be a predictor of osteoporosis induced by low calcium intake. Periconceptional multivitamin supplementation has reduced the risk of serious birth defects, premature delivery, and low birth weight by 50% and improved maternal health during pregnancy. Micronutrients of particular importance for prevention of adverse pregnancy outcomes are folic acid, zinc, and iron. However, if the preterm delivery is caused by preeclampsia, then data suggest that calcium supplementation and high doses of vitamins C and E significantly reduce that risk. Well-controlled studies consistently have shown that calcium supplementation, with or without vitamin D, significantly reduces the risk of hip fracture. Antioxidants such as vitamins C and E have been shown to reduce the risk of fracture in women smokers. As in the rapidly growing embryo, the immune system includes rapidly multiplying cells whose functions are dramatically affected by an individual's micronutrient status. Multivitamins have been shown to enhance many aspects of immune response, and antioxidant micronutrients consistently have been found to enhance lymphocyte-proliferative responses and skin-test responses, especially in the elderly.

Folic acid supplements during pregnancy and risk of miscarriage

BACKGROUND

Although taking supplements that contain 400 microg of folic acid before and during early pregnancy reduces a woman's risk for having a baby with a neural-tube defect (NTD), the effects of such supplements on other pregnancy outcomes remain unclear. We examined whether the use of such supplements affects the occurrence of miscarriage.

METHODS

Participants were women in China who had taken part in a recent folic acid campaign to prevent NTDs and who had registered in this campaign before they became pregnant for the first time. We examined the risk for miscarriage among women who had confirmed pregnancies and who had or had not taken pills containing only 400 microg of folic acid before and during early pregnancy.

RESULTS

The overall rate of miscarriage was 9.1% (2155/23806). The rates of miscarriage among women who had and had not taken folic acid pills before and during the first trimester were 9.0% and 9.3%, respectively (risk ratio 0.97 [95% CI 0.84-1.12]). The distributions of gestational age at pregnancy diagnosis and at miscarriage were similar for both groups of women.

INTERPRETATION

In this population-based study of a cohort of women whose use of folic acid supplements while pregnant had been previously documented and who had been pregnant for the first time, we found no evidence that daily consumption of 400 microg of folic acid before and during early pregnancy influenced their risk for miscarriage.

Modelling the potential impact of population-wide periconceptional folate/multivitamin supplementation on multiple births

OBJECTIVE

To develop a model of the impact of population-wide periconceptional folate supplementation on neural tube defects and twin births.

DESIGN

A hypothetical cohort of 100,000 pregnancies > or =20 weeks, plus terminations of pregnancy after prenatal diagnosis before 20 weeks.

METHODS

Application of pooled data on the relative risks for neural tube defects and twins following periconceptional folate from meta-analysis of the randomised trials.

MAIN OUTCOME MEASURES

1. Pregnancies with a neural tube defect (i.e. terminations of pregnancy, perinatal deaths, and surviving infants); 2. twin births (i.e. preterm births, perinatal deaths, postneonatal deaths, birth defects, cerebral palsy); 3. numbers needed to treat.

RESULTS

The change in neural tube defects would be 75 fewer terminations (95% CI -47, -90), 30 fewer perinatal deaths (95% CI 18, -35), and 13 fewer surviving infants with a neural tube defect (95% CI -8, -16). The change in twinning would be an additional 572 twin confinements (95% CI -100, +1587), among whom there would be 63 very preterm twin confinements (95% CI -11, +174), 54 perinatal and postneonatal deaths (95% CI -9, +149), 48 surviving twins with a birth defect (95% CI -8, +133), and nine with cerebral palsy (95% CI -2, +26). The numbers needed to treat for the prevention of one pregnancy with a neural tube defect is 847, for the birth of one additional set of twins is 175, for the birth of one additional set of very preterm twins is 1587, and for the birth of an additional twin with any of the following outcomes (perinatal death, postneonatal death, survival with a birth defect, or survival with cerebral palsy) is 901.

CONCLUSIONS

Monitoring rates of neural tube defects and twinning is essential as supplementation or fortification with folate is implemented.

Folate fortification: potential impact on folate intake in an older population

OBJECTIVE

To examine the potential impact of different models of folate fortification of Australian foods on the folate intakes of older Australians.

DESIGN

Dietary data were collected using a food frequency questionnaire from people attending a population-based health study.

SETTING

Two postcode areas west of Sydney, Australia.

SUBJECTS

A total of 2895 people aged over 49 y, obtained from a door knock census (79% of 3654 subjects examined).

MAIN OUTCOME MEASURES

The folate intake in this population was estimated using four different models: (1) pre-fortification folate values; (2) current voluntary folate fortification in Australia; (3) universal fortification of all foods permitted to add folate, at 25% recommended dietary intake (RDI) per reference serve; and (4) universal fortification of all foods permitted to add folate, at 50% RDI per reference serve. The increased bioavailability of synthetic folic acid (SFA) was included in the analysis.

RESULTS

At current voluntary folate fortification, approximately 65% of this population consume 320 microg dietary folate equivalents (DFE) or more per day from diet and supplements, and 0.4% (n=10) consume greater than the recommended upper safety level of 1000 microg from SFA. More than 95% of this older population would be expected to consume more than 320 microg DFE from diet and supplements with universal fortification at 50% of the RDI, and 0.5% (n=14) may consume greater than 1000 microg/day of SFA.

CONCLUSIONS

There is unlikely to be a large increase in the proportion of older persons who are likely to consume more than the upper safety level of intake with universal folate fortification. As most of those who currently or are predicted to consume over 1000 microg SFA take supplements containing folic acid, it is highly recommended that vitamin B12 be included in any vitamin supplements containing folate.

SPONSORSHIP

This study was supported by the Australian National Health and Medical Research Council (NHMRC).

Prevention of birth defects: folic acid

Neural tube defects (NTDs) comprise an important category contributing to infant mortality. While some NTDs may be due to identifiable inherited or specific environmental factors, most are multifactorial, with genetic and environmental factors contributing to their occurrence. Folic acid has been found to have a protective effect against the recurrence and occurrence of NTDs. In addition to natural dietary sources, in the United States, all enriched grain products now are fortified with folic acid. In addition, all women who could become pregnant are recommended to consume 0.4 mg of folic acid daily. Despite these measures, not all women of childbearing age have added sufficient folic acid to their diets or take a vitamin supplement. Challenges remain regarding educating women of childbearing age about the potential health benefits of adequate folic acid consumption.

Fetal malformations and folate metabolism: review of recent evidence

Although a reduction in incidence of neural tube defects is unequivocally linked to adequate folate status, evidence is also mounting associating folate with other fetal malformations. The emerging discoveries about single nucleotide polymorphisms have given new insight into folate biochemistry, enabling more precise understanding of how genetic variations influence folate-dependent pathways in embryogenesis. Findings suggest that folate status may be partly under genetic control, and may involve a "cocktail effect" resulting from interactions among genes, nutrients, and enzymes. Despite major laboratory advances, much of the human evidence comes from observational studies, and questions linger that cannot be definitively answered without randomized clinical trials.

Folate, homocysteine and neural tube defects: an overview

Folate administration substantially reduces the risk on neural tube detects (NTD). The interest for studying a disturbed homocysteine (Hcy) metabolism in relation to NTD was raised by the observation of elevated blood Hcy levels in mothers of a NTD child. This observation resulted in the examination of enzymes involved in the folate-dependent Hcy metabolism. Thus far, this has led to the identification of the first and likely a second genetic risk factor for NTD. The C677T and A1298C mutations in the methylenetetrahydrofolate reductase (MTHFR) gene are associated with an increased risk of NTD and cause elevated Hcy concentrations. These levels can be normalized by additional folate intake. Thus, a dysfunctional MTHFR partly explains the observed elevated Hcy levels in women with NTD pregnancies and also, in part, the protective effect of folate on NTD. Although the MTHFR polymorphisms are only moderate risk factors, population-wide they may account for an important part of the observed NTD prevalence.

Association between polymorphisms of folate- and methionine-metabolizing enzymes and susceptibility to malignant lymphoma

Genetic alteration is considered a probable cause of malignant lymphoma. Folate and methionine metabolism play essential roles in DNA synthesis and DNA methylation, and their metabolic pathways might thus affect disease susceptibility. In the present study, 2 polymorphisms were evaluated for a folate metabolic enzyme, methylenetetrahydrofolate reductase (MTHFR), and one was evaluated for methionine synthase (MS). The 2 polymorphisms, MTHFR677 C-->T and MTHFR1298 A-->C, are reported to reduce the enzyme activity, which causes intracellular accumulation of 5,10-methylenetetrahydrofolate and results in a reduced incidence of DNA double-strand breakage. The MS2756 A-->G polymorphism also reduces the enzyme activity and results in the hypomethylation of DNA. To evaluate the association between malignant lymphoma susceptibility and these polymorphisms, hospital-based case-control study was conducted in Aichi Cancer Center. Ninety-eight patients with histologically confirmed lymphoma and 243 control subjects without cancer were evaluated. Unconditional logistic regression analyses revealed a higher susceptibility with the MTHFR677 CC and the MTHFR1298 AA genotypes (odds ratio, 2.26; 95% confidence interval, 1.26-4.02) when those harboring at least one variant allele in either polymorphism of MTHFR were defined as the reference. For the MS polymorphism, the MS2756 GG genotype also showed a higher susceptibility (odds ratio, 3.83; 95% CI, 1.21-12.1) than those with MS2756 AA or AG types. The significance was not altered when these 3 polymorphisms were evaluated in combination, and the results suggest that folate and methionine metabolism play important roles in the occurrence of malignant lymphomas. Further studies to confirm the association and detailed biologic mechanisms are now required.

A screen for mutations in human homologues of mice exencephaly genes Tfap2alpha and Msx2 in patients with neural tube defects

BACKGROUND

Very little is known about the identity of genetic factors involved in the complex etiology of nonsyndromic neural tube defects (NTD). Potential susceptibility genes have emerged from the vast number of mutant mouse strains displaying NTD. Reasonable candidates are the human homologues of mice exencephaly genes Tfap2alpha and Msx2, which are expressed in the developing neural tube.

METHODS

A single-strand conformation analysis (SSCA) mutation screen of the coding sequences of TFAP2alpha and MSX2 was performed for 204 nonsyndromic NTD patients including cases of anencephaly (n = 10), encephalocele (n = 8), and spina bifida aperta, SBA (n = 183). A selected number of SBA patients was additionally tested for specific mutations in MTHFD, FRalpha, and PAX1 already shown to be related to NTD.

RESULTS

Two TFAP2alpha point mutations in individual SBA patients were silent on the amino acid level (C308C, T396T). On nucleic acid level, these mutations change evolutionary conserved codons and thus may influence mRNA processing and translation efficiency. One SBA patient displayed an exonic 9-bp deletion in MSX2 leading to a shortened and possibly less functional protein. None of these mutations was found in 222 controls. Seven polymorphisms detected in TFAP2alpha and MSX2 were equally distributed in patients and controls. Patients with combined heterozygosity of an exonic MSX2 and an intronic TFAP2alpha polymorphism were at a slightly increased risk of NTD (OR 1.71; 95% CI 0.57-5.39).

CONCLUSIONS

Although several new genetic variants were found in TFAP2 and MSX2, no statistically significant association was found between NTD cases and the new alleles or their combinations. Further studies are necessary to finally decide if these gene variants may have acted as susceptibility factors in our individual cases.

Importance of folate in human nutrition

From a public health perspective, some of the new insights into folic acid nutrition are of significance. Folate intake recommendations vary under different conditions. Intake of 350 microg is required to maintain plasma homocysteine levels, 650 microg for those with elevated plasma homocysteine, about 400 microg for women planning to become pregnant and 4000 microg for those with history of neural tube defect affected pregnancy. This raises the question whether the folate intake is adequate for the general population, particularly in the vulnerable groups or whether there is a need for scientists to take a fresh view of the requirements, recommended dietary intakes, and consider intervention measures which will have impact on the folate nutritional status. The recommendations should provide a margin of safety to allow for decreased intake, increased requirements, individual variability and bioavailability of natural food folates. The folate intake and nutriture in relation to India and other developing countries needs careful consideration to reduce anemia, neural tube defects and possibly impact on the high incidence of cardiovascular diseases.

Do we need another randomized controlled trial of folic acid alone?

As a public health strategy to help prevent neural tube defect-affected pregnancies, enriched flour and pasta in the United States and Canada are being fortified with folic acid, and women are being advised to take supplementary folic acid around the time of pregnancy to ensure an adequate intake. But in spite of the recently published results of a public health campaign in China, the burden of proof that folic acid alone is responsible for a decreased risk of these birth defects rests on the results of a randomized controlled trial conducted by the Medical Research Council of the United Kingdom. Supporting evidence comes primarily from studies that have shown a protective effect of multivitamins containing folic acid as one of many nutrients. Based on a striking and potentially hazardous type of non-compliance observed in an earlier study in which a participant took multiple vitamin doses simultaneously and a suggestion of similar incidents in the Medical Research Council study, we conclude that a further randomized controlled trial of the protective effect of folic acid alone may be necessary.