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

Neural tube defects in Victoria, Australia: potential contributing factors and public health implications

OBJECTIVES

To measure population prevalence and determine potential predictors of neural tube defects.

METHOD

Analysis of all births reported to a mandated collection of perinatal data, and terminations prior to 20 weeks' gestation that have been reported to a data collection of birth defects in Victoria from 1983 to 1997. Prevalence at birth and risk ratios of infant and maternal characteristics associated with neural tube defects were calculated.

RESULTS

Prevalence of spina bifida has remained steady for 15 years and was 8.8/10,000 in 1997. Anencephaly increased to 7.9/10,000 in 1997. After exclusion of pregnancy terminations, the 1997 birth prevalence was 4.5/10,000 for spina bifida and 2.4/10,000 for anencephaly. Neural tube defects are identified in 1 in 1600 fetuses, the risk being significantly higher for epileptic women (Adjusted Odds Ratio (AOR) = 3.70, 95% CI 2.25-6.07), multiple births (AOR = 4.56, 95% CI 3.46-6.02), teenage mothers (AOR = 1.47, 95% CI 1.09-2.00) compared with those aged 25-29, and women with three or more previous pregnancies (AOR = 1.40, 95% CI 1.10-1.78). The risk was lower for women of East Asian (AOR = 0.70, 95% CI 0.49-1.00) and Middle Eastern origin (AOR = 0.60, 95% CI 0.35-1.02) and these differences were approaching statistical significance.

CONCLUSION

Total prevalence of neural tube defects did not decline up to 1997.

IMPLICATIONS

It is unlikely that targeting 'at risk' groups identified in this study would make a difference to neural tube defect incidence. However, consideration could be given to identifying larger 'at risk' groups such as those with homocysteine metabolism defects.

Folic acid supplementation

Neural tube defects represent one of a limited number of congenital conditions for which primary prevention strategies are available. Despite strong clinical evidence to support the preventive effect of supplementary folic acid given prior to conception and continued throughout the first 12 weeks of pregnancy, there is limited recent epidemiological data to support the effectiveness of national folic acid supplementation programs. Whether folic acid fortification of staple foods will provide a more effective means of achieving further reductions in the prevalence rates for this condition remains open to question. Recent advances associating folic acid supplementation, hyperhomocysteinaemia and neural tube defects provide a new insight into the possible pathological mechanism of this and possibly other related congenital conditions.

Folic acid antagonists during pregnancy and the risk of birth defects

BACKGROUND

Multivitamin supplementation in pregnant women may reduce the risks of cardiovascular defects, oral clefts, and urinary tract defects in their infants. We evaluated whether the folic acid component of multivitamins is responsible for the reduction in risk by examining the associations between maternal use of folic acid antagonists and these congenital malformations.

METHODS

We compared data on exposure to folic acid antagonists that act as dihydrofolate reductase inhibitors and to certain antiepileptic drugs for 3870 infants with cardiovascular defects, 1962 infants with oral clefts, and 1100 infants with urinary tract defects with data for 8387 control infants with malformations the risk of which is not reduced after vitamin supplementation. Mothers were interviewed within six months after delivery about their medication use.

RESULTS

The relative risks of cardiovascular defects and oral clefts in infants whose mothers were exposed to dihydrofolate reductase inhibitors during the second or third month after the last menstrual period, as compared with infants whose mothers had no such exposure, were 3.4 (95 percent confidence interval, 1.8 to 6.4) and 2.6 (95 percent confidence interval, 1.1 to 6.1), respectively. The relative risks of cardiovascular defects, oral clefts, and urinary tract defects after maternal exposure to antiepileptic drugs were 2.2 (95 percent confidence interval, 1.4 to 3.5), 2.5 (95 percent confidence interval, 1.5 to 4.2), and 2.5 (95 percent confidence interval, 1.2 to 5.0), respectively. Use of multivitamin supplements containing folic acid diminished the adverse effects of dihydrofolate reductase inhibitors, but not that of antiepileptic drugs.

CONCLUSIONS

Folic acid antagonists, which include such common drugs as trimethoprim, triamterene, carbamazepine, phenytoin, phenobarbital, and primidone, may increase the risk not only of neural-tube defects, but also of cardiovascular defects, oral clefts, and urinary tract defects. The folic acid component of multivitamins may reduce the risks of these defects.

Anemia and deficiencies of folate and vitamin B-6 are common and vary with season in Chinese women of childbearing age

Little is known about the micronutrient status of Chinese women of childbearing age. We assessed nonfasting plasma concentrations of folic acid, vitamin B-12, vitamin B-6 (as pyridoxal-5'-phosphate), hemoglobin (Hb), ferritin and transferrin receptor (TfR) in 563 nonpregnant textile workers aged 21-34 y from Anqing, China. All women had obtained permission to become pregnant and were participating in a prospective study of pregnancy outcomes. Mean (SD) plasma concentrations were 9.7 (4.1) nmol/L folic acid, 367 (128) pmol/L vitamin B-12, 40.2 (15.8) nmol/L vitamin B-6, 108 (12. 9) g/L Hb, 42.6 (34.2) microgram/L ferritin and 5.2 (2.7) mg/L TfR. Twenty-three percent of women had biochemical evidence of folic acid deficiency, 26% were deficient in vitamin B-6 and 10% had low vitamin B-12. Overall, 44% of women were deficient in at least one B vitamin. Although anemia (Hb < 120 g/L) was detected in 80% of women, only 17% had depleted iron stores (ferritin < 12 microgram/L); 11% had elevated TfR concentrations. Distinct seasonal trends were observed in the prevalence of moderate anemia (Hb < 100 g/L) and deficiencies of folic acid and vitamin B-6, with significantly lower concentrations of folate and Hb occurring in summer and lower concentrations of vitamin B-6 occurring in winter and spring than in other seasons. We conclude that deficiencies of folic acid, vitamin B-6 and iron were relatively common in this sample of Chinese women of childbearing age and were contributing to the high prevalence of anemia. Without appropriate supplementation, these deficiencies could jeopardize the women's health and increase their risk of adverse pregnancy outcomes.

Primary prevention of neural-tube defects and some other major congenital abnormalities: recommendations for the appropriate use of folic acid during pregnancy

Neural-tube defects (NTDs) are common and serious congenital abnormalities of the central nervous system. Although some cases of NTDs are induced by hyperhomocysteinaemia, resulting from genetic polymorphism of a thermolabile enzyme, in the majority of cases the cause is unknown. Diet supplementation with a folic acid-containing multivitamin or high dose of folic acid alone in the periconception period reduced the recurrence of NTDs by 83 to 91% and 71%, respectively. Two Hungarian intervention studies demonstrated a high efficacy for periconception multivitamin supplementation (containing a physiological dose: 0.8mg of folic acid) in the primary prevention of the first occurrence of an NTD (approximately 92% reduction in the incidence of NTDs). However, a high dose of folic acid (approximately 6mg) alone during the periconception period was less efficient. Periconception folic acid-containing multivitamin supplementation reduces the occurrence of urinary tract and cardiovascular congenital abnormalities, and congenital limb deficiencies. The occurrence of orofacial cleftings may also be reduced by a high dose of folic acid. This preventive effect may be the result of other mechanisms of action (e.g. compensation of impaired mitosis caused by a folate deficiency). There are 3 options for ensuring appropriate multivitamin/folic acid consumption for women of childbearing age. First, providing a folate- and other vitamin-rich diet, which unfortunately may not be appropriate for this purpose. Second, and perhaps the best choice, the unique opportunity for multivitamin/folic acid supplementation during the periconception period. However, a major proportion of pregnancies are unplanned and, even in planned pregnancies, this type of primary prevention has not been widely used. Furthermore, it would require changes to the previous recommendations since a multivitamin containing a physiological dose of folic acid (0.5 to 0.8mg) seems to be more effective in reducing the occurrence of the first NTD and other congenital abnormalities than folic acid alone. Periconception multivitamin supplementation may also reduce the occurrence of recurrent NTDs. Thirdly, food (e.g. flour, bread) may be fortified with folic acid or 3 B vitamins (folic acid, B 12 and B6). This provides a practical means to ensure all women, especially those from lower socioeconomic backgrounds and/or with a low level of education who are more likely to have unplanned pregnancies, have an adequate folic acid intake.

Clinical and laboratory features and sequelae of deficiency of folic acid (folate) and vitamin B12 (cobalamin) in pregnancy and gynecology

Classically, deficiency of folic acid (folate) or vitamin B12 (cobalamin) was recognized by the presence of a macrocytic anemia resulting from megaloblastic changes in the bone marrow. A markedly changing paradigm has identified both new mechanisms for altered folate and cobalamin status and new sequelae and clinical interrelationships that include altered mechanisms of absorption, a changing pattern of neurologic deficits, an increased risk of vascular occlusive lesions, and an important relationship with the mechanisms of neoplastic transformation. Several of these newer characterizations relate to issues of neoplasia in the nonpregnant woman and to issues in pregnancy, such as the potential for developmental abnormalities of the fetal nervous system.

Japanese couples' childbirth experiences in Michigan: implications for care

BACKGROUND

Subtle cultural differences in the childbirth experience for expatriate Japanese couples living in southeast Michigan can sometimes cause conflicts between them and American health caregivers. The purpose of this study was to examine Japanese couples' perceptions and experiences of prenatal care and childbirth in a region of the United States, and to explore the implications for providing culturally competent care.

METHODS

In this qualitative study, in-depth interviews of 11 Japanese couples (n = 22) were conducted at an outpatient primary care clinic in southeast Michigan by a team of researchers fluent in the Japanese language and knowledgeable about the culture. Participants also completed a short questionnaire.

RESULTS

The major themes that emerged comprised perceptions related to a language barrier, ultrasonography, prenatal vitamin supplementation, episiotomy, epidural anesthesia, and practitioner-patient relationship. Throughout these six themes it was evident that Japanese health care professionals had difficulty accepting health care that was different from the care provided in their home country.

CONCLUSION

The most striking finding of this study was the difficulty for health caregivers to provide culturally competent care. Although the program has strongly invested in health professionals and support staff who were fluent in Japanese and knowledgeable about Japanese culture, conflicts still occurred.

College women's awareness and consumption of folic acid for the prevention of neural tube defects

PURPOSE

Awareness and consumption of folic acid in the context of neural tube defect prevention among college women were assessed.

METHODS

Subjects documented folic acid awareness and multivitamin consumption. Beliefs about folic acid before and after an educational intervention were characterized using the Health Belief Model (HBM) and the Fetal Health Locus of Control Scale (FHLCS).

RESULTS

Awareness of folic acid was not associated with multivitamin consumption. Belief variables were not associated with awareness or consumption of folic acid.

CONCLUSION

This study does not support educational interventions based on the HBM or FHLCS to increase multivitamin consumption among college women.

Investigation of folate pathway gene polymorphisms and the incidence of neural tube defects in a Texas hispanic population

Neural tube defects (NTDs) are multifactorial in their etiology, having both genetic and environmental factors contributing to their development. Recent evidence demonstrates that periconceptional supplementation of the maternal diet with a multivitamin containing folic acid significantly reduces the occurrence and recurrence risk for having a pregnancy complicated by NTDs. Unfortunately, the mechanism underlying the beneficial effects of folic acid remains unknown. NTD surveillance data from the Texas-Mexico border show that the high NTD rate (28/10,000 live births) noted during the 1990-1991 Cameron county NTD cluster was superimposed on a background Cameron county NTD rate (16/10,000 live births) which is considerably higher than that generally noted in the United States (8-10/10,000 live births). These data suggest that genetic factors as well as transient environmental factors may contribute to the etiology of the NTDs. Furthermore, clinical and experimental evidence imply that allelic forms of genes involved with folate metabolism and/or transport may explain some of the observed variation in the NTD rates found across different populations. Two folate pathway genes were selected for evaluation in this study. The loci investigated included two known alleles of the 5, 10-methylenetetrahydrofolate reductase (MTHFR) gene, as well as the promoter region of the folate receptor-alpha (FR-alpha) gene. Odds ratios (ORs) for the C677T polymorphism in the MTHFR gene were 1.8 (CI 0.47-6.8) for heterozygosity and 1.8 (CI 0.35-9.4) for homozygosity for the mutant 677T allele, relative to wildtype homozygotes. The odds ratio for the heterozygosity for the A1298C polymorphism in the same gene was 1.1 (CI 0.09-14). No individuals homozygous for the 1298C allele were observed. The OR for heterozygosity of FR-alpha gene polymorphisms detected at nucleotide 762 and at nucleotides 610/631 was 1.4 and 0.7, respectively. Neither of the FR-alpha polymorphisms was observed in the homozygous condition. No statistically significant associations were observed for any of the polymorphisms examined, as the 95% confidence intervals for all of the ORs included one. However, the frequency of the MTHFR 677T allele in the largely Hispanic control group from Texas was significantly different from other populations (P < 0.005), and among the highest reported for any control populations examined.

Periconceptional supplementation with folate and/or multivitamins for preventing neural tube defects

BACKGROUND

Neural tube defects arise during the development of the brain and spinal cord.

OBJECTIVES

The objective of this review was to assess the effects of increased consumption of multivitamins or folate on the prevalence of neural tube defects before pregnancy and in the first two months of pregnancy (periconceptionally).

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group trials register.

SELECTION CRITERIA

Randomised and quasi-randomised trials comparing periconceptional supplementation by multivitamins with placebo, folate with placebo, or multivitamins with folate; different dosages of multivitamins or folate; prepregnancy dietary advice and counselling in primary care settings to increase the consumption of folate-rich foods, or folate-fortified foods, with standard care; increased intensity of information provision with standard public health dissemination.

DATA COLLECTION AND ANALYSIS

Two reviewers assessed trial quality and extracted data.

MAIN RESULTS

Four trials involving 6425 women were included. The trials all addressed the question of supplementation and they were of variable quality. No dissemination trials were identified. Periconceptional folate supplementation reduced the incidence of neural tube defects (odds ratio 0.28, 95% confidence interval 0.15 to 0.53). Folate supplementation did not significantly increase spontaneous abortion, ectopic pregnancy or stillbirth, although there was a possible increase in multiple gestation. Multivitamins alone were not associated with prevention of neural tube defects and did not produce preventive effects when given with folate.

REVIEWER'S CONCLUSIONS

Periconceptional folate supplementation has a strong protective effect against neural tube defects. Information about folate should be made more widely available throughout the health and education systems. Women whose fetuses or babies have neural tube defects should be offered continuing folate supplementation. The benefits and risks of fortifying basic food stuffs, such as flour, with added folate remain unresolved.