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PubMed2005

International retrospective cohort study of neural tube defects in relation to folic acid recommendations: are the recommendations working?

OBJECTIVES: To evaluate the effectiveness of policies and recommendations on folic acid aimed at reducing the occurrence of neural tube defects. DESIGN: Retrospective cohort study of births monitored by birth defect registries. SETTING: 13 birth defects registries monitoring rates of neural tube defects from 1988 to 1998 in Norway, Finland, Northern Netherlands, England and Wales, Ireland, France (Paris, Strasbourg, and Central East), Hungary, Italy (Emilia Romagna and Campania), Portugal, and Israel. Cases of neural tube defects were ascertained among liveborn infants, stillbirths, and pregnancy terminations (where legal). Policies and recommendations were ascertained by interview and literature review. MAIN OUTCOME MEASURES: Incidences and trends in rates of neural tube defects before and after 1992 (the year of the first recommendations) and before and after the year of local recommendations (when applicable). RESULTS: The issuing of recommendations on folic acid was followed by no detectable improvement in the trends of incidence of neural tube defects. CONCLUSIONS: Recommendations alone did not seem to influence trends in neural tube defects up to six years after the confirmation of the effectiveness of folic acid in clinical trials. New cases of neural tube defects preventable by folic acid continue to accumulate. A reasonable strategy would be to quickly integrate food fortification with fuller implementation of recommendations on supplements.

Abortion, Induced↗

PubMed1995

A genetic defect in 5,10 methylenetetrahydrofolate reductase in neural tube defects.

It is now well-established that folic acid, taken peri-conceptionally, can reduce the risk of neural tube defects (NTDs). Recent work has demonstrated that an abnormality of homocysteine metabolism is a critical factor. The gene for 5,10 methylenetetrahydrofolate reductase, an enzyme important in homocysteine metabolism, was studied in relation to NTDs. To determine the frequency of the allele for the thermolabile form of the reductase, DNA samples were collected from people with NTDs, parents of people with NTDs, and normal controls. Of 82 people with NTDs, 15 (18.3%) were homozygous for the abnormal, thermolabile allele. This was significantly higher (p = 0.01) than the rate of 6.1% in the control population (odds ratio 3.47, 95% CI 1.28-9.41). This is the first specific genetic abnormality to be identified in NTDs. It explains the association between some NTDs and elevated homocysteine, given that the reductase is important in homocysteine metabolism. It also explains how folic acid supplementation prevents some NTDs, by overcoming a partial block in the conversion of 5,10 methylenetetrahydrofolate to 5 methyltetrahydrofolate. Genetic screening could identify women who will require folic acid supplements to reduce their risk of having a child with an NTD.

Case-Control Studies↗

PubMed2006

Risk factors for neural tube defects: a study at university-affiliated hospitals in Tehran.

BACKGROUND: Neural tube defects have a complex and imperfectly understood etiology involving both genetic and environmental factors. In this case-control study, we tried to determine the association of known risk factors for neural tube defects in patients referred to university-affiliated hospitals with neurosurgical services in the city of Tehran. METHODS: Risk factors were assessed in-person through interviews with infants' mothers. We found 192 neural tube defect cases. One hundred and ninety-three apparently normal babies were randomly selected from the same hospitals to serve as control cases. RESULTS: Maternal age of less than 18 years (P = 0.02), female sex of the child (P = 0.01), birth in spring and summer seasons (P = 0.001), history of not using folic acid (P = 0.001), less than 5 prenatal visits (P = 0.001), and poverty (P = 0.02) were the most important risk factors for neural tube defects. Logistic regression analysis of these risk factors confirmed these correlations. A negative history of consuming folic acid had the most significant statistical correlation with these malformations. CONCLUSION: Poor quality diets were an important environmental risk factor in this study.

Adolescent↗

PubMed2006

Weekly administration of folic acid and epidemiology of neural tube defects.

OBJECTIVE: In 1999, a folic acid campaign for prevention of neural tube defects was started in Nuevo León, México, with the recommendation of taking a 5000 -mcg tablet of folic acid per week. The purpose of this study was to compare the epidemiology of neural tube defects after four years of the campaign. METHODS: Cases of anencephaly, spina bifida, and encephalocele (ICD Q00, Q01, Q05, 10th Ed.) from public and private hospitals were registered by immediate notification, death certificates, and fetal death registries. Comparisons of neural tube defects rates, phenotype distribution of cases, and sex ratios, registered before and after the folic acid campaign, were done using the Student's t Test and Chi square test. RESULTS: There was a 50% reduction in the incidence of anencephaly and spina bifida cases from 93 in 1999 (1.04x1000) to 46 in the year 2003 (0.56x1000) (p<0.001). Spina bifida cases declined up to 70% in 2002 and anencephaly cases up to 50% in 2003. In 1999, overall, the ratio (females: males) was 0.66 with female excess; the sex ratio was similar for anencephaly and spina bifida cases. In the year 2000, female cases showed a significant reduction for both spina bifida and anencephaly (75% and 56% respectively); the sex ratio was 0.57 with a greater male excess for both phenotypes. CONCLUSIONS: Weekly administration of 5000 mcg of folic acid reduces the incidence of neural tube defects 50%, primarily spina bifida, with a higher reduction of female cases.

Anencephaly↗

PubMed1983

Early morphological abnormalities in splotch mouse embryos and predisposition to gene- and retinoic acid-induced neural tube defects.

Genetic and environmental factors contribute to an individual's neural tube defect liability. In the mouse, the gene mutation Splotch (Sp) causes a pigmentation defect in heterozygotes while homozygotes have spina bifida +/- exencephaly. Splotch homozygotes, heterozygotes, and wild-type embryos were examined for somite number, anterior neuropore closure, and posterior neuropore length. The aim was to distinguish potentially affected homozygotes early in pathogenesis and find a morphological basis for increased teratogen susceptibility in heterozygotes. Posterior neuropore closure as well as anterior neuropore closure was significantly delayed in potentially affected Sp as compared to wild-type litter embryos exceeding the incidence found in day-10-diagnosed homozygotes. Part of this excess was attributed to a transient delay in heterozygotes which in turn might predispose to retinoic acid-induced neural tube defects. This idea was supported by an outcross of Sp heterozygote males by inbred SWV females and wild-type males by SWV where a significant increase in retinoic acid-induced neural tube defects was found in Sp carrier litters.

Animals↗

PubMed1993

Changing trend of neural tube defects in eastern Turkey.

STUDY OBJECTIVE: The aim was to study the relationship between birth prevalence of neural tube defect (including anencephaly) in Eastern Turkey before and after the Chernobyl disaster. DESIGN: This was a prospective study of time trends in live births and stillbirths over the years 1985-1990. Medical and sociodemographic data were recorded for the mothers. SETTING: Elazig, Eastern Turkey. SUBJECTS: There were 5240 live births and stillbirths during the study period, 24 of whom had neural tube defect and of these 20 had anencephaly. MAIN RESULTS: Of the 5240 newborns, 24 had a neural tube defect, giving a birth prevalence of 4.5 per 1000 total births. Of these, 20 were anencephalic (3.8 per 1000). In all, of the 2355 conceptions estimated to have occurred prior to the Chernobyl disaster in May 1986, the birth prevalences of total neural tube defect and anencephaly were the same (1.7 per 1000). This contrasts with the years following after Chernobyl, when the birth prevalence of total neural tube defect was 6.9 per 1000 (5.5 per 1000 for anencephaly). The differences were statistically significant (p < 0.001). These two increased rates reached a peak of 12.4 (for total neural tube defects) and 8.9 (for anencephaly) in 1988. In 1989 the rate of total neural tube defects decreased to 10.0 and that of anencephaly to 8.6 per 1000. In 1990 the rate of total neural tube defects fell to 5.6 and that of anencephaly fell to 4.2. CONCLUSIONS: The changes in birth prevalence of neural tube defects might be due to the Chernobyl disaster. However, the increases observed occurred mainly in infants conceived well over a year after the Chernobyl disaster, suggesting that other factors may be responsible.

Air Pollution, Radioactive↗

PubMed1992

Spectrum of neural-tube defects in 34 infants prenatally exposed to antiepileptic drugs.

We analyzed the spectrum of neural-tube defects associated with maternal exposure to antiepileptic drugs (AEDs) and the possible contribution of familial and genetic factors to epilepsy or neural-tube defects. No specific association with maternal family history of neural-tube defects or epilepsy was seen. The ratio of spina bifida to anencephaly (33:1) suggested a specific association with caudal defects. Hydrocephaly was documented in at least 21 cases. Other midline defects, all associated with valproate (VPA), were hypospadias (two), hypertelorism (two), partial agenesis of corpus callosum, agenesis of septum pellucidum with lissencephaly of medial sides of occipital lobes, Dandy-Walker anomaly, and ventricular septal defect. This study shows that most neural-tube defects following maternal VPA use are severe open defects. They are frequently complicated by hydrocephaly and other midline defects. Prenatal diagnosis is possible.

Anticonvulsants↗

PubMed1993

Prevalence of neural tube defects in South Australia, 1966-91: effectiveness and impact of prenatal diagnosis.

OBJECTIVE: To determine trends in total prevalence of neural tube defects in South Australia during 1966-91, the impact of prenatal diagnosis on birth prevalence, and the effectiveness of prenatal screening for neural tube defects in 1986-91. DESIGN: All births and terminations of pregnancy affected by neural tube defects and information on prenatal screening were ascertained from multiple sources including the South Australian perinatal and abortion statistics collections, birth defects register, and state maternal serum alpha fetoprotein screening programme. SETTING: Southern Australia. SUBJECTS: All 1058 births and terminations of pregnancy affected by neural tube defects in 1966-91. MAIN OUTCOME MEASURES: Total prevalence and birth prevalence of individual and all neural tube defects. The proportion of screened cases detected prenatally. RESULTS: Total prevalence of neural tube defects during 1966-91 was 2.01/1000 births with no upward or downward trend. However, birth prevalence fell significantly (by 5.1% a year), with an 84% reduction from 2.29/1000 births in 1966 to 0.35/1000 in 1991 (relative risk = 0.16, 95% confidence interval 0.07 to 0.34). The fall was 96% for anencephaly and 82% for spina bifida. 85% of defects, both open and closed, were detected before 28 weeks' gestation in women screened by serum alpha fetoprotein or mid-trimester ultrasonography, or both, in 1986-91 (99.0% for anencephaly and 75.7% for spina bifida). CONCLUSIONS: While the total prevalence of neural tube defects in South Australia remained stable, prenatal diagnosis and termination of pregnancy resulted in an 84% fall in birth prevalence during 1966-91. Screening detected over four fifths of cases in 1986-91.

Confidence Intervals↗

PubMed1992

An epidemiologic study of neural tube defects: Delta County, Michigan, 1969-1988.

We determined the incidence of neural tube defects (anencephaly, spina bifida, hydrocephalus) in a rural county in the Upper Peninsula of Michigan because several local physicians perceived that the incidence in this area might be high. To assure that all neural tube defects that occurred were noted, data for the study were collected from hospital birth-log books, patient records of all neural tube defect births, all stillbirth records, and from records of babies transferred to other regional hospitals. A reference group consisting of 10% of all nonneural tube defect births during the 20 years of the study was selected at random and used to make comparisons to the case group. During the twenty-year period 1969-1988, the incidence of neural tube defects (NTDs) was found to be 2.09 per 1000 total births. The incidence of anencephaly was 1.05/1000; of spina bifida, 0.56/1000; and for hydrocephalus, 0.48/1000. Seasonal variations by month of conception were noted for anencephaly and spina bifida, confirming previous findings in the literature. Study results showed that between 1972 and 1976 there was a cluster of NTDs, but the NTD incidence was not statistically different from what might be expected over a twenty-year period. The incidence of NTDs in Delta County was found to be normal for this part of North America. The results of this study indicate that physicians should be cautious when attempting to interpret rare events, which often occur in clusters, leaving the impression that their incidence is excessive.

Adult↗

PubMed1976

Amniotic fluid alpha-fetoprotein as a marker in prenatal diagnosis of neural tube defects.

The prenatal diagnosis of anencephaly and spina bifida (neural tube defect, NTD) through amniotic fluid analysis for alpha-fetoprotein (AFP) is gradually gaining clinical recognition. AFP concentrations were determined in 237 amniotic fluids from normal pregnancies ranging between 7 and 42 weeks of gestation. A steady decline in AFP from 26 mug/ml at 7-9 weeks to 155 ng/ml at term is observed. AFP concentration was determined in 35 amniotic fluids from 33 confirmed neural tube defective pregnancies. In 14 cases where amniotic fluid was examined prior to the 26th week of gestation. AFP was markedly elevated when compared with the normal range of the same gestational period. In 21 amniotic fluids past the 26th week, 17 cases (85-) had markedly elevated AFP levels; however, 2 cases of anencephaly, 1 of spina bifida, and 1 of hydrocephaly gave levels within the normal range. It is concluded that elevated AFP in the amniotic fluid is a reliable but nonspecific marker for open neural tube defects prior to the 26th week of pregnancy, but may become normal after the 26th week in a small percentage of patients.

Amniotic Fluid↗

PubMed2002

Association of low maternal education with neural tube defects in Colorado, 1989-1998.

Despite increasing use of folate prior to conception, neural tube defects remain among the most common birth defects in the United States. The Study objective was to investigate the maternal and child characteristics associated with having an infant born with a neural tube defect (NTD) in Colorado between 1989 and 1998. Data were derived from a population-based case control study of all live-born infants in Colorado from 1989 to 1998 (n=551,285), utilizing birth certificate records and a statewide neural tube defect registry. Chi-square analysis and multiple logistic regression were used to assess the strength of association between sociodemographic characteristics and the main outcome measure, the birth of a child with an NTD. Final analysis was limited to those children born to mothers who themselves were born in either the United States or Mexico. In this ten-year period, there were 251 confirmed cases of NTDs in Colorado, 224 of whom were born to women who were born in either the United States or Mexico. Significant bivariate associations were found between NTDs and the following: female sex of the child, lower maternal age, maternal country of birth in Mexico, and maternal education less than tenth grade. The single strongest predictor of having a child with an NTD was low maternal education (adjusted OR 1.8, 95% CI 1.1-3.1). Low maternal education is an important predictor of having a child with an NTD. In order to further reduce the incidence of neural tube defects, interventions should target women of low educational status.

Adult↗

PubMed1982

Ultrasonography and alpha-fetoprotein determination for antenatal detection of neural tube defects.

We review our experience in the antenatal detection of neural tube defects in a collaborative study between the prenatal diagnostic program of the Section of Medical Genetics and the Ultrasound Laboratory at the West Virginia University. In West Virginia the incidence of neural tube defects is two to three times the national average. The patients were referred to the sonic laboratory for a variety of reasons, even though they had not been classified in the high risk category. Our data confirm the advantage of ultrasonography for screening of the population in the early stages of pregnancy. The study also confirmed the value of serum and amniotic fluid alpha-fetoprotein (AFP) determination in conjunction with ultrasonography, especially when there is a positive family history. The combination of modalities appears to be the best means at present for detection of these severe disorders. Screening the general population in the early stages of pregnancy by means of ultrasonography, a noninvasive technic, can help to review fetal maturity and placental localization, as well as to detect neural tube defects. High risk mothers can then be followed up by further evaluations using serum or amniotic fluid AFP studies.

Amniotic Fluid↗

PubMed1981

Prenatal detection of neural tube defects by maternal serum alphafetoprotein assay.

Mass screening for fetal neural tube defects using maternal serum alpha-fetoprotein assay as the initial test is financially justified in South Africa, despite the relatively low incidence of these defects in this country, using enzyme-linked immunosorbent assay. This technique is efficient and inexpensive and lends itself to mass screening. We report a pilot study in which 3153 maternal serum samples were received during a 4-month period. Of these 3102 were assayed and the outcome of pregnancy was recorded in 2069 cases. On the first assay 147 (4.7%) of the women had serum alpha-fetoprotein levels which were high for the gestational dates given, but in retrospect about half of these had been misinterpreted because of incorrect dates. Among the remainder, 6 women proved to be carrying twins, 4 aborted spontaneously, 10 delivered prematurely or had infants with intra-uterine growth retardation, and 4 had a fetus with a neural tube defect. Two affected fetuses were missed by screening, in both cases because serum was taken after 20 weeks gestation. In this sample the incidence in Indians (1/1000)and Coloureds (1/600) was as expected, but in Whites it was much higher (1/130), which probably reflects a sampling error and indicates that the epidemiology of neural tube defects in South Africa requires investigation.

Adolescent↗

PubMed1996

Blood folic acid and vitamin B12 in relation to neural tube defects.

OBJECTIVE: To determine the relation between blood folic acid and serum vitamin B12 in neural tube defect pregnancies using data from the MRC Vitamin Study and a literature review of all studies. DESIGN: Stored blood samples collected as part of a randomised trial of vitamin supplementation in the prevention of neural tube defects were retrieved from affected pregnancies (cases) and unaffected pregnancies (controls). Four controls were matched with each case by centre, maternal age and duration of storage of the blood sample. The samples had been collected from women at entry to the trial, immediately before the women became pregnant, and at around 12 weeks of pregnancy. Our results were combined with those already published from other studies to obtain an overall assessment of blood folic acid and vitamin B12 in relation to neural tube defects. SETTING: Blood samples were collected as part of the MRC Vitamin Study. The collaborating centres were in the United Kingdom, Hungary, Israel, Australia, Canada and Russia. PARTICIPANTS: Twenty-seven women with neural tube defect pregnancies and 108 matched controls with unaffected pregnancies. RESULTS: Serum and red cell folic acid and serum vitamin B12 levels were lower in the cases than in controls at each of the three occasions when blood samples were collected, but no comparison was significant (P > 0.05). A systematic review of all studies from the literature showed that on average, during the 1st trimester of pregnancy, serum folic acid was 0.6 ng/ml lower in neural tube defect pregnancies (P < 0.01), red cell folic acid was 77 ng/ml lower (P < 0.001) and serum vitamin B12 was 38 ng/l lower (P < 0.001). A logistic regression showed no association between serum B12 and neural tube defects after allowing for serum folic acid. CONCLUSION: our results are consistent with other evidence that folic acid and vitamin B12 levels are lower in women with neural tube defect pregnancies and consistent with evidence from randomised trials which showed that folic acid is protective.

Female↗

PubMed1987

A sonographic sign which predicts which fetuses with hydrocephalus have an associated neural tube defect.

We report a sonographic sign which reliably distinguishes those hydrocephalic fetal heads associated with a neural tube defect from those which are not, particularly in the second trimester. This sign involves a "pointed" deformity of the frontal aspect of the skull in fetuses with hydrocephalus, indicating the presence of a neural tube defect. A retrospective review of 36 cases of hydrocephalus demonstrates that this sign is particularly helpful in the second trimester, where it was present in all the fetuses with hydrocephalus and neural tube defect. It was less reliable in the third trimester; however, this sign was not present in any of the fetuses with hydrocephalus who did not have a neural tube defect. Angulation or pointing of the fetal frontal bone when hydrocephalus is present, particularly in the second trimester, seems to be a reliable predictor of an associated neural tube defect and mandates a careful search for this defect.

Female↗

PubMed1984

Epidemiology of neural tube defects in Utah, 1940-1979.

The prevalence and distribution of 991 cases of neural tube defects who were born in Utah in 1940-1979 are analyzed. The average prevalence at birth is 1.00 per 1000 births (live and stillbirths), which is similar to other states in the western United States. A decline in prevalence is observed during the past 10 years, although there is not a long-term secular trend for the whole time period. Examination of hospital records shows that 17.9% of neural tube defects were not reported on birth or fetal death certificates. The male/female sex ratio is 0.67. No seasonality is found for spina bifida cases; however, a bimodal distribution, with a substantial deficit in May, is observed for anencephaly. A significant negative correlation is found between neural tube defect prevalence and the percentage of individuals in each Utah county who are members of the Mormon Church. No association is found between levels of fallout exposure in Utah and regional variation in neural tube defects, and time-space clustering analysis demonstrates no significant clusters of neural tube defects in Utah.

Anencephaly↗

PubMed1993

Neural tube defects and serum zinc.

OBJECTIVE: To investigate the relationship of zinc in the causation of neural tube defects and so explore the possible role as a cause of these defects. DESIGN: Stored serum samples collected as part of the Medical Research Council's multicentre randomised trial section of vitamin supplementation in the prevention of neural tube defects were retrieved in respect of women who had had an affected pregnancy together with four matched unaffected controls per case. One control was selected from each of the four randomisation groups: 1. no extra vitamins; 2. folic acid supplementation alone; 3. folic acid and other vitamin supplementation; and 4. other vitamin supplementation, such that it was matched with an NTD case by study centre, maternal age (the year of birth differed at most by one year) and duration of storage of the serum sample (in most instances to within the same year). SETTING: A prospective case-control study using serum samples stored at -40 degrees C. The serum samples were collected from women at entry to the trial, immediately before the women became pregnant and at about 12 weeks of pregnancy. SUBJECTS: Twenty-seven women with a pregnancy associated with a neural tube defect and 108 matched controls with unaffected pregnancies. RESULTS: There was no association between serum zinc levels and neural tube defects; the mean values in microgram/dl were: 82 and 85 in cases and controls, respectively, at entry to the study; 86 and 87 micrograms/dl just before pregnancy; and 76 and 80 micrograms/dl in the first trimester of pregnancy. Folic acid supplementation did not have an effect on serum zinc levels. CONCLUSION: Within the range of serum zinc levels observed among women in our study, serum zinc is not a cause of neural tube defects, and periconceptional folic acid supplements do not compromise the zinc status of the mother or the embryo with respect to zinc intake.

Case-Control Studies↗

PubMed1986

Recurrent neural tube defects, risk factors and vitamins.

Data from our trial of periconceptional vitamin supplementation for the prevention of neural tube defects have been analysed to assess the influence of various factors on recurrence rates of neural tube defect. Our data suggest that the risk of recurrence of neural tube defect is influenced by the number of previous neural tube defects, area of residence, immediately prior miscarriage, and interpregnancy interval. None of these factors, however, contributed any significant differential risk between supplemented and unsupplemented mothers. Hence we conclude that the highly significant difference in recurrence rates of neural tube defect between supplemented and unsupplemented mothers was due to vitamin supplementation.

Abortion, Spontaneous↗