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PubMed1991

Vitamin deficiencies and neural-tube defects: human and animal studies.

The evidence for an association between vitamin deficiency in early pregnancy and the prevalence of neural-tube defects in humans is reviewed, with particular emphasis on the methodological problems encountered in conducting such studies. It is apparent that there is strong evidence for an association between maternal vitamin status and the outcome of pregnancy, but this is not universally accepted, due to ethical and practical constraints on the design of the studies. There are also problems in obtaining precise information from experiments on animals in vivo. By culturing rat embryos in dialysed serum in which the micromolecular component is defined, it has been possible to demonstrate that significant numbers of neural-tube defects can be produced by the deficiency of a single vitamin (inositol), and that multiple vitamin deficiency produces a further significant increase in the frequency of such defects.

Animals↗
PubMed1984

Amniotic fluid analysis in prenatal diagnosis of neural tube defects: a comparison between six biochemical tests supplementary to the measurement of amniotic fluid alpha-fetoprotein.

Concanavalin A (con A) and lens culinaris agglutinin (LCA) microheterogeneity pattern of AFP (crossed affinity immunoelectrophoresis), alpha-2-macroglobulin and synaptic membrane protein D-2 (rocket immunoelectrophoresis) and qualitative (polyacrylamide gel electrophoresis) and quantitative (enzyme kinetic reaction rate) acetylcholinesterase were analysed in 87 consequtive samples from normal pregnancies and 37 abnormal samples (fetal neural tube defect or abdominal wall defect). Very few false positive results were obtained in normal pregnancies with any of the tests. In all cases of neural tube defects the correct result was obtained with qualitative acetylcholinesterase analysis, whereas only 2/3 of the abdominal wall defects were correctly predicted. Testing with con A or LCA was less optimal in neural tube defects, whereas all abdominal wall defects could be predicted correctly. Acetylcholinesterase in the quantitative test and protein D-2 did not decrease the rate of false results. Determination of the alpha-2-macroglobulin concentration performed well in the present study, but is not recommended because of the very high susceptibility to contamination of amniotic fluid with fetal or maternal blood.

Abdominal Muscles↗
PubMed1998

Neural-tube defects are associated with low concentrations of cobalamin (vitamin B12) in amniotic fluid.

While folate supplementation reduces the risk of recurrent neural-tube defects (NTD), both folate and cobalamin deficiencies may be independent risk-factors for neural-tube defects. Folate-dependence and impaired remethylation of homocysteine are implicated as mechanisms for NTD. There are few references reported for folate, cobalamin, homocysteine and methionine in the fetal compartment. This case-controlled pilot study of amniotic fluid (AF) samples derived from 16 NTD pregnancies and 64 age-matched controls quantities total homocysteine (tHcy), total cysteine (tCys), folate, cobalamin (B12), and methionine. Only decreased AF B12 concentrations were found (150 pg/ml versus 540 pg/ml, P < 0.02). Since cobalamin, folate and homocysteine participate in the remethylation of homocysteine, via methyl transfer from 5-methyltetrahydrofolate to B12, to methionine, we compared ratios of these methionine synthase (EC 2.1.1.13)-related intermediates. The ratio of B12/folate for NTD versus controls was 48 (34-90) versus 126 (123-182), P < 0.001. The ratio of methionine/(folate x tHcy) was 1.4 (1.2-2.2) versus 2.7 (2.4-3.3), P < 0.001. We conclude that AF from pregnancies with NTD have lower B12 concentrations, and that ratios of product to substrate(s) of homocysteine remethylation suggest impaired methionine synthase in the fetal compartment through the early second trimester.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1995

CD1+ cells in mothers of stillborn infants with neural tube defects.

In healthy individuals, CD1+ cells are found in thymic- tissue, but not in peripheral blood. The thymus, as a key organ of the neuroendocrine system, frequently shows gross abnormalities in infants with neural tube defects. In order to study the immunologic significance of fetal thymic findings, maternal T-lymphocyte subpopulations were investigated. In 10 mothers of healthy newborns, 5 mothers of stillborn infants who had no gross abnormalities, and 5 mothers of stillborn infants with neural tube defects, CD1+, CD3+, CD4+, and CD8+ cells were studied. Only the mothers of the infants with open neural tube defects showed CD1+ cells in their peripheral blood.

Antigens, CD↗
PubMed1995

Mid-second trimester organic acids in severe open neural tube defects.

OBJECTIVE: To investigate amnioic fluid organic concentrations at 16 weeks gestation from normal fetuses and those affected by severe neural tube defects. METHODS: Amniotic fluid collected from normal, anencephalic and severe open spina bifida fetuses was analysed for up to 24 organic acids by gas liquid chromatography. RESULTS: Significant increase in organic acids similar to those observed in defects of phenylalanine and tyrosine metabolism were identified when compared with the normal fetuses. Significant differences in organic acid concentrations were also identified within the two neural tube defect groups. CONCLUSION: A relationship between phenylalanine and tyrosine metabolism, closure rate of the neural tube and folate metabolism is proposed.

Amniocentesis↗
PubMed1987

Neural tube defects and sex ratios.

The sex ratio of 147 fetuses with presumed multifactorial neural tube defect (NTD) was studied. Overall, the ratio (males:females) was 0.73 with expected female excess. However, when the NTDs were subdivided according to the site of the lesion, the sex ratios varied. Total craniorachischisis, anencephaly with cervical spina bifida, holoacrania, and thoracic spina bifida showed a greater female excess than that overall; the sex ratio for meroacrania was close to unity, while that for low spinal lesions, particularly those involving the sacrum, showed an extreme bias towards males. These findings are related to the mode of formation of the neural tube. Females seem prone to defects of neurulation and males to defects in canalization. An explanation for these findings is suggested in possible sex differences in rate of early embryonic development.

Anencephaly↗
PubMed1986

Neural tube defects: heterogeneity and homogeneity.

Detailed investigations were made on 150 fetuses with neural tube defects (NTD). After eliminating those with recognised causes, the rest were found to consist of fetuses with both isolated NTD and NTD with other developmental abnormalities. On evaluation of reproductive history, type and frequencies of NTD in pregnancies before conception, and sex of the fetuses involved, no demonstrable difference between these two types of NTD was found. Secondly, in those with additional developmental abnormalities, a significant clustering of developmental defects rather than a uniform distribution throughout abnormalities were found predominantly in cases of total craniorachischisis and upper thoracic spina bifida, less often in anencephaly and thoraco-lumbar spina bifida, and never in lumbo-sacral spina bifida. Thus it appears that there is not a random concurrence of other developmental abnormalities with NTD but a definite pattern. We suggest that this implies a connection between the developmental abnormality and the NTD and that the additional abnormalities arise due to mechanical induction by the particular specific disturbance of the neural tube and its surrounding tissues. The most important difference between isolated NTD and those with other associated abnormalities is that the disruption in development at neurulation is more far reaching in the latter than in the former.

Abortion, Spontaneous↗
PubMed2003

ACOG practice bulletin. Neural tube defects. Number 44, July 2003. (Replaces committee opinion number 252, March 2001).

Neural tube defects (NTDs) are congenital structural abnormalities of the brain and vertebral column that occur either as an isolated malformation, along with other malformations, or as part of a genetic syndrome. Isolated (ie, nonsyndromic) NTDs occur in 1.4-2 per 1,000 pregnancies and are the second most common major congenital anomaly worldwide (cardiac malformations are first). In the United States, approximately 4,000 fetuses are affected each year of which one third are either aborted or spontaneously lost. Anencephaly accounts for one half of all cases of NTDs and is incompatible with life; with treatment, 80-90% of infants with spina bifida survive with varying degrees of disability. Most importantly, NTDs are among the few birth defects for which primary prevention is possible; prenatal screening and diagnosis are widely available, and prenatal therapy is being investigated.

Biomarkers↗
PubMed2002

Neural-tube defect in dizygotic twins.

Despite the strong association between twinning and neural-tube defects (NTD), concordance of twins with NTDs is very rare. A case of concordant NTDs in dizygotic twins is reported in view of its extreme rarity.

Adult↗
PubMed2004

High rates of neural tube defects in Ukraine.

BACKGROUND: Oral consumption of synthetic folic acid can prevent neural tube defects (NTDs), which are some of the most severe congenital anomalies. The prevalence of NTDs in Ukraine and other countries of the former U.S.S.R. has not been well studied. We determined the prevalence of NTD-affected pregnancies in Northwestern Ukraine as background for policy decisions related to flour fortification in this country. METHODS: The Ukrainian-American Birth Defects Program was established in 1999 and conducts population- based surveillance of birth defects in several oblasts (states) of Ukraine. We determined the prevalence of NTDs in the Volyn and Rivne oblasts of Northwestern Ukraine for three years, 2000-2002. RESULTS: There were 75,928 births in the two oblasts in 2000-2002. There were 159 cases of NTDs among live births, stillbirths, and induced abortions. The prevalence of NTDs in the two oblasts in Northwestern Ukraine is 2.1 per 1000 births. CONCLUSIONS: The prevalence of NTD-affected pregnancies we found in Northwestern Ukraine is almost four times what it should be. This prevalence suggests that population folate deficiency is widespread in Ukraine. Universal folic acid fortification of flour milled in Ukraine is urgently needed to end this epidemic of birth defects. Such fortification would be expected to prevent folate deficiency anemia, heart attacks, and strokes.

Female↗
PubMed1997

Inositol prevents folate-resistant neural tube defects in the mouse.

Clinical trials demonstrate that up to 70% of neural tube defects (NTDs) can be prevented by folic acid supplementation in early pregnancy, whereas the remaining NTDs are resistant to folate. Here, we show that a second vitamin, myo-inositol, is capable of significantly reducing the incidence of spinal NTDs in curly tail mice, a genetic model of folate-resistant NTDs. Inositol increases flux through the inositol/lipid cycle, stimulating protein kinase C activity and upregulating expression of retinoic acid receptor beta, specifically in the caudal portion of the embryonic hindgut. This reduces the delay in closure of the posterior neuropore, the embryonic defect that is known to lead directly to spina bifida in curly tail embryos. Our findings reveal a molecular pathway of NTD prevention and suggest the possible efficacy of combined treatment with folate and inositol in overcoming the majority of human NTDs.

Animals↗
PubMed1992

Maternal vitamin levels during pregnancies producing infants with neural tube defects.

Women at very high risk for having a child with a neural tube defect (NTD) because they had previously delivered affected children significantly reduced their recurrence rate by taking folate supplements before conception. To clarify how these results might apply to a lower-risk general obstetric population, we measured folate, vitamin B12, and retinol levels in maternal serum drawn early in 89 pregnancies resulting in NTD offspring and 178 control pregnancies identified from the Finnish Registry of Congenital Malformations. In 86.5% of the subjects, specimens were collected within 8 weeks after neural tube closure. In the NTD case mothers the mean (+/- SD) levels were not significantly lower than in control mothers: folate, 4.13 +/- 2.36 versus 4.28 +/- 2.52 ng/ml; vitamin B12, 482.8 +/- 161.1 versus 520.3 +/- 191.9 pg/ml; and retinol, 51.2 +/- 17.0 versus 50.5 +/- 16.9 micrograms/dl. After adjustment for age of the specimen, gestational age at which the specimen was drawn, maternal age, and maternal employment status, the odds ratios for being a case mother were 1.00 (95% confidence interval (CI) 0.91 to 1.10) for folate, 1.05 (95% CI 0.92 to 1.19) for vitamin B12, and 0.99 (95% CI 0.88 to 1.10) for retinol. Excluding NTD cases with known or suspected causes unrelated to vitamins, restricting the analyses to interviewed subjects, and excluding subjects whose specimens were collected after 15 gestational weeks confirmed that NTD case and control vitamin levels did not differ significantly. This population-based investigation in a low rate area demonstrated no relationship between maternal serum folate, vitamin B12, or retinol levels during pregnancy and the risk of NTDs.

Adult↗
PubMed1988

Environmental factors in the etiology of neural tube defects: a negative study.

A case-control study was made on women who had an infant with a neural tube defect and twice as many controls. Cases and controls were selected from a national medical birth registry from which prospectively collected data on previous pregnancy, contraceptive use, and smoking were also retrieved. Women's occupation was either retrieved from that registry or from census information which was partially checked with direct interview. Information on environmental characteristics of the place of living of the women in early pregnancy was given by field workers who were unaware of the status of case or control. Cases and controls showed no statistically significant difference with regard to previous pregnancies and use of contraceptives at or the month before the time of conception. Case women smoked 10 cigarettes or more a day slightly more often than control women did but the difference was not statistically significant. No statistically significant difference in occupation distribution was seen between cases and controls (but cases had slightly more occupations where chemical exposure is likely), and no differences in home environment could be found. It is concluded that the factors studied play no major etiological role for the origin of neural tube defects in Sweden.

Abnormalities, Drug-Induced↗
PubMed1986

[Prenatal diagnosis of neural tube defects. Value of electrophoresis of cholinesterases].

Cholinesterase electrophoresis was performed in 802 amniotic fluids and its value in the detection of neural tube defects was compared with those of ultrasonography and amniotic fluid alpha-foetoprotein levels. Cholinesterase electrophoresis confirmed the ultrasonic diagnosis in 51 cases of neural tube abnormality and made it possible to diagnose neural tube defect in 6 other cases which had remained undetected by ultrasound and by alpha-foetoprotein level measurements. When our technique is used before the 28th week of gestation, false-positive results concern abnormalities which are easily detected by ultrasound (omphalocele, Bonnevie-Ullrich syndrome, sacrococcygeal tumour). We did not observe any false-negative result.

Amniotic Fluid↗
PubMed2003

Inositol- and folate-resistant neural tube defects in mice lacking the epithelial-specific factor Grhl-3.

The neural tube defects (NTDs) spina bifida and anencephaly are widely prevalent severe birth defects. The mouse mutant curly tail (ct/ct) has served as a model of NTDs for 50 years, even though the responsible genetic defect remained unrecognized. Here we show by gene targeting, mapping and genetic complementation studies that a mouse homolog of the Drosophila grainyhead (grh) gene, grainyhead-like-3 (Grhl3), is a compelling candidate for the gene underlying the curly tail phenotype. The NTDs in Grhl3-null mice are more severe than those in the curly tail strain, as the Grhl3 alleles in ct/ct mice are hypomorphic. Spina bifida in ct/ct mice is folate resistant, but its incidence can be markedly reduced by maternal inositol supplementation periconceptually. The NTDs in Grhl3-/- embryos are also folate resistant, but unlike those in ct/ct mice, they are resistant to inositol. These findings suggest that residual Grhl3 expression in ct/ct mice may be required for inositol rescue of folate-resistant NTDs.

Animals↗
PubMed1991

Transcobalamins in the etiology of neural tube defects.

In a sample of 79 pregnant women at risk offspring with neural tube defects (NTDs) and 158 controls, significantly increased median values were found for apo-transcobalamins I and II in amniotic fluid in the group at risk, thus confirming previous results. The findings may reflect a genetic disposition to NTDs associated with altered levels of apo-transcobalamins, and research on the etiology and mechanisms of NTDs should focus on these proteins.

Adult↗
PubMed1987

Impact of genetic counseling and prenatal diagnosis for Down syndrome and neural tube defects.

In two parallel studies the impact of genetic counseling and prenatal diagnosis upon family planning decisions was evaluated for parents of a child with Down syndrome and for parents of a child with neural tube defect. One hundred and nineteen parents of a child with standard trisomy 21 volunteered to participate in study I; 94 parents who had a neural tube defect child took part in study II. Each study included three groups of parents: one group received genetic counseling, another group had already an amniocentesis performed and a third group of parents had neither received genetic counseling nor had they an amniocentesis performed. Data collection took place by means of interviews by a social nurse at the parents' home. An exhaustive questionnaire was used to guide the interview and to assess the total impact of the birth of the affected child as completely as possible. Some years later additional follow-up information was gathered by sending a questionnaire to all families. In both studies a significantly better recall of the relevant risk figures was found in the counseled group as compared with the group of parents who did not receive genetic counseling. The relationship between the recalled risk and its subjective interpretation was very complex. The information given during the counseling session(s) influenced more than half of the parents of a child with Down syndrome, to decide in favour of further pregnancies. In the group of parents having a child with neural tube defect the information received at the genetic counseling session(s) even had a more important effect: 80 percent decided to plan another pregnancy. Results of both studies clearly indicate that for more than half of the families the availability of prenatal diagnosis was of crucial importance in the decision to plan future pregnancies.

Amniocentesis↗
PubMed1983

Antenatal screening for neural tube defects in South African blacks.

The place of antenatal screening for open neural tube defects is well established throughout the Western world. Alphafetoprotein assay, followed by amniocentesis in selected instances and the option of termination if proved necessary, is accepted as a means of attempting to minimize the many insoluble problems associated with the birth of children afflicted with spina bifida. Nowhere in South Africa is routine screening attempted in Black expectant mothers. The reasons for this are discussed and the feasibility of introducing a screening programme in the Durban area is evaluated.

Black or African American↗