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PubMed1997

[A correlation study on homocysteine metabolism in pregnant women and neural tube defects in urban and rural areas].

Serum levels of homocysteine, folic acid and vitamin B12 in pregnant women in urban and rural areas were compared to study the relationship between homocysteine metabolism and neural tube defects. Four hundred and eleven serum specimens were sampled randomly from a serum bank for women with early pregnancy in Beijing area, 195 from urban and 216 from rural. Their levels of homocysteine were determined by high performance liquid chromatography combined with electrochemical methods, and those of folic acid and vitamin B12 by radioimmunoassay. Results showed that level of homocysteine was significantly higher in rural pregnant women than that in urban, with 9.31 mumol/L and 5.73 mumol/L, respectively, level of vitamin B12 was lower in rural than that in urban women, with 210.09 pmol/L and 233.35 pmol/L, respectively, and level of folic acid was higher in rural than that in urban women, but no significant difference in deficiency of folic acid between rural and urban was found. The average ratio of folic acid to homocysteine and that of vitamin B12 to homocysteine were higher in rural than those in urban women. It suggests that abnormal metabolism of homocysteine usually correlates with high incidence of neural tube defects in rural area.

Adult↗
PubMed1986

Causes of windowing-induced dysmorphogenesis (neural tube defects and early amnion deficit spectrum) in chicken embryos.

Previous reports suggest that windowing the shells of chicken eggs during the first day of incubation frequently results in dysmorphogenesis of the central nervous system. We report here data that further delineate the neural tube defects associated with this animal model. In addition, we describe another birth defect syndrome associated with windowing: the early amnion deficit spectrum (EADS). Several components of the egg are altered structurally by windowing: the shell, outer and inner shell membranes, yolk, and air space at the blunt end of the egg. A new air space is formed over the embryo as the original one at the blunt end is obliterated. A series of studies (pH, oxygen and carbon dioxide tensions, relative humidity, temperature, and deformation of the yolk documented with magnetic resonance imaging) examining individual steps of the windowing procedure and additional techniques that stimulate windowing suggest that mechanical stress causes isolated neural tube defects and dehydration causes amnion defects. These amnion defects are associated with other embryonic abnormalities suggestive of deformations consistent with EADS.

Amnion↗
PubMed2005

Brain tissue fragments in the amniotic fluid of rats with neural tube defect.

AIMS: Brain tissue nodules are occasionally seen in the lungs of neural tube defect (NTD) cases. We looked for brain tissue fragments in amniotic fluid of rats with NTD as it is the basis for the aspiration hypothesis. METHODS: Eighty-seven pregnant rats were randomly divided into experimental (n=58) and control (n=29) groups. Experimental rats received 100,000 U of vitamin A in 1 mL of corn oil on gestational days 8, 9 and 10, while control rats received corn oil. On gestational days 15, 18, 19, 20 and 21, amniotic fluid was drawn from three control animals and five experimental animals and analysed. RESULTS: NTD was found in 22.75% of experimental fetuses and in no control fetuses. Brain tissue fragment number and volume fraction increased between gestational days 18 and 20, falling on day 21. CONCLUSIONS: Excessive doses of vitamin A induce a high rate of early fetal death and development of NTD. Brain tissue fragments in the amniotic fluid reflect the evolution from exencephaly to anencephaly and could support the aspiration hypothesis. However, as it is a late event in the rat, this model may not reproduce the brain tissue nodules in the lung.

Amniotic Fluid↗
PubMed2004

Epidemiology of neural tube defects and folic acid.

This review article combines four disparate observations about Neural Tube Defects (NTDs). They are the worldwide decline in the birth incidence that began prior to prenatal diagnosis; family recurrence risks; the effect of prenatal diagnosis and termination of affected pregnancies; and the effect of folic acid.

Editorial↗
PubMed1976

Antenatal diagnosis of neural tube defects.

One hundred women with pregnancies at risk for the recurrence of neural tube defects have entered our monitoring programme of echography and alphafetoprotein estimation (AFP) on amniotic fluid and maternal serum during the second trimester. The results of these pregnancies, the application of the programme, sources of error, and the reliability of alphafetoprotein levels are discussed. Conclusions regarding the value of the tests and routine antenatal screening are made.

Adult↗
PubMed1982

Fetal neural tube defects detected by rocket-on-line immunoelectrophoresis of amniotic fluids.

Immunization of rabbits with human fetal brain membranes evoked antisera with reactivity against D-2 protein from brain and cerebrospinal fluid. In amniotic fluids from pregnancies with fetal neural tube defects the presence of D2-protein could be demonstrated by rocket-on-line immunoelectrophoresis. In a prospective study on 72 amniotic fluids with increased alphafetoprotein concentration neural tube defects were correctly predicted in 26 pregnancies. One false-negative and four false-positive pregnancies were encountered. D2-protein determination may thus have a role in antenatal diagnosis of neural tube malformations as a supplement to alphafetoprotein analysis.

Amniocentesis↗
PubMed1997

Sequence analysis of the coding region of human methionine synthase: relevance to hyperhomocysteinaemia in neural-tube defects and vascular disease.

Elevated homocysteine (Hcy) levels are observed in two apparently unrelated diseases: neural-tube defects (NTD) and premature vascular disease. Defective human methionine synthase (MS) could result in elevated Hcy levels. We sequenced the coding region of MS in 8 hyperhomocysteinaemic patients (4 NTD patients and 4 patients with pregnancies complicated by spiral arterial disease, SAD). We identified only one mutation resulting in an amino acid substitution: an A-->G transition at bp 2756, converting an aspartic acid (D919) into a glycine (G). We screened genomic DNA for the presence of this mutation in 56 NTD patients, 69 mothers of children with NTD, 108 SAD patients and 364 controls. There was no increased prevalence of the GG and AG genotypes in NTD patients, their mothers or SAD patients. The D919G mutation does not seem to be a risk factor for NTD or vascular disease. We then examined the mean Hcy levels for each MS genotype. There was no correlation between GG- or AG-genotype and Hcy levels. The D919G mutation is thus a fairly prevalent, and probably benign polymorphism. This study, though limited, provides no evidence for a major involvement of MS in the aetiology of homocysteine-related diseases such as NTD or vascular disease.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1999

Time trends in neural tube defects prevalence in relation to preventive strategies: an international study.

OBJECTIVE: To examine time trends in neural tube defects (NTD) prevalence from 1987 to 1996 in relation to the primary prevention policies for folic acid supplementation strategies in different countries. DESIGN: Retrospective time trends analysis of NTD prevalence. SETTING: 11 birth defect registries of congenital malformations participating in the International Clearinghouse for Birth Defects Monitoring System, in the period from 1 July 1987 to 30 June 1996. SUBJECTS: 8207 live births, stillbirths and terminated pregnancies affected by anencephaly or spina bifida registered by the 11 participating centres 1987-1996. OUTCOME MEASURES: Prevalence rate ratios based on the annual rates, using the Poisson regression model. RESULTS: During the study period a significant fall in prevalence rates for all NTD is present in Atlanta (USA), England and Wales, Hungary and Japan, and a significant rise in Norway and South America. After adjusting for the secular trends observed in the earlier years of the study, no significant trend can be attributed to preventive strategies. Data on NTD prevalence are supplemented with information on folate awareness among some of the populations studied. CONCLUSION: There is no evidence that, up to the middle of 1996, any change in time trend was attributable to the introduction of national folate supplementation policies. The possible effectiveness of folate supplementation policies for the reduction of NTD clearly needs to be tried and studied for several more years. Considering that in the Western world about 50% of pregnancies are unplanned, a policy that rests on action taken before conception can only have limited success. Strategies based on food enrichment, such as was introduced in the USA from the beginning of 1998, may prove to be more successful.

Female↗
PubMed2003

Neural tube defects: knowledge and preconceptional prevention practices in minority young women.

OBJECTIVE: To assess 1) knowledge of neural tube defect (NTD) prevention by folic acid, 2) frequency of intake of multivitamins and folate- and folic acid-fortified food, and 3) factors associated with knowledge and prevention practices among sexually active minority adolescent and young adult women. METHODS: Young minority women were enrolled in a folic acid program at 3 urban Houston, Texas, reproductive health clinics and assessed for NTD knowledge and preventive practices. A 3-month supply of multivitamins was also dispensed at enrollment. A 3-month program follow-up survey of a randomly selected sample at 2 sites was conducted. RESULTS: Of 387 women (mean age: 18 +/- 1.9 years), 72% were black and 28% were Hispanic. At enrollment, clinics were a major source of information of NTD prevention (44%); 52% had heard of folic acid, 45% had heard of NTDs, and 50% had heard of birth defects prevention by multivitamins. Significantly more Hispanic than black young women had heard of NTDs (59% vs 39%). Pregnancy history, regular birth control use, and education level for age were independently associated with knowledge. In young women with low education level for age, regular birth control use was significantly associated with knowledge. At enrollment, daily multivitamin intake was very low (9%) and folate-rich foods were consumed in inadequate amounts. Adequate folate diet was not associated with knowledge. The program follow-up survey indicated that 88% to 92% had knowledge of NTDs and folic acid, and 67% reported taking a daily multivitamin. CONCLUSIONS: Publicly funded clinics may be the only source of information on NTD prevention for many minority young women. Preliminary evidence suggests that a promotion program improves knowledge, and dispensing of multivitamins increases multivitamin use. However, clinicians in such programs need to reinforce daily adherence to multivitamins in young women.

Adolescent↗
PubMed2003

Analysis of the human folate receptor beta gene for an association with neural tube defects.

The folate receptor beta (FRbeta) gene encodes a receptor that binds and transports 5-methyltetrahydrofolate. FRbeta polymorphisms may potentially alter folate delivery and are likely candidates for an association with neural tube defect (NTD) risk. To look for association between FRbeta polymorphisms we studied NTD-affected children and their parents (254 triads) recruited throughout Ireland and a control population of 296 pregnant women who did not give birth to an NTD-affected child. Five potential single nucleotide polymorphisms (SNPs) were examined. These were located within the coding, intronic and 3(')-untranslated regions of the FRbeta gene. Four of these SNPs were not found to be variable within our Irish cohort. SNP rs651646 (A-->T), located upstream of exon 2 within an intronic region, is polymorphic and is thus a marker for an FRbeta NTD association study. The frequency of the SNP rs651646 "A" allele was not significantly different in cases (odds ratio [OR] 1.07, 95% CI. 0.84-1.36; P=0.60), their mothers (odds ratio [OR] 1.09, 95% CI. 0.86-1.38; P=0.51) or fathers (odds ratio [OR] 1.09, 95% CI. 0.86-1.38; P=0.50) when compared to controls. Comparisons of allele transmission from 255 informative heterozygous parents of NTD cases showed no preferential transmission of either the A or T alleles (A: 50.2%, n=128; T: 49.8%, n=127; P=1.00, McNemar chi(2) 0.0). We also measured allele frequencies in a sample of American-Caucasians and African-Americans. Highly significant allele frequency differences were observed between populations. In conclusion, SNP rs651646 within the FRbeta gene is polymorphic but is not associated with neural tube defects within the Irish population.

3' Untranslated Regions↗
PubMed1978

Prenatal diagnosis of neural tube defects through amniotic fluid measurements.

On the basis of our experience with 1314 prospective diagnoses for neural tube defects, we continue to rely on amniotic fluid AFD as the primary and most reliable indicator. The problem of fetal blood contamination has to be tackled in a quantitative manner, and an attempt made to estimate the likely contribution from fetal serum based on measurements of the proportion of fetal erythrocytes in the mixture. We also recommend estimation of the macrophage proportion at 18 hours in the cultured amniotic fluid cells, and a detailed examination of the morphology of cells that adhere, at this time, to the culture surface. An outline of the procedure that we currently employ in handling amniocentesis samples is shown in Figure 3.

Amniocentesis↗
PubMed2000

[The common C677T polymorphism in the methylenetetrahydrofolate reductase gene is associated with neural tube defects and preeclampsia].

OBJECTIVE: To assess whether methylenetetrahydrofolate reductase(MTHFR) gene C677T polymorphism is associated with neural tube defects and preeclampsia. METHODS: Twenty- four mothers who had given birth to normal children, 27 mothers who had given birth to NTDs children, 120 normal women, and 57 women who had suffered from preeclampsia were genotyped for C677T polymorphism by using PCR/RFLP method. RESULTS: (1) VV genotype frequency in the normal mothers group it was 0.13, while in the NTDs mothers group it was 0.33; mothers with VV genotype were at 3 times increased risk to have a NTDs child, compared with the normal mothers. (2) In the normal women group VV genotype frequency was 0.15, while in the preeclampsia women group it was 0.31; women with VV genotype were at 2.5 times increased risk to have preeclampsia, compared with the normal women. CONCLUSION: The authors believe that MTHFR VV genotype is associated with the development of NTDs and preeclampsia.

Female↗
PubMed2006

Alpha-fetoprotein detection of neural tube defects and the impact of standard ultrasound.

OBJECTIVE: The purpose of this study was to evaluate neural tube defect (NTD) detection according to whether serum alpha-fetoprotein (AFP) screening or standard ultrasound are performed. STUDY DESIGN: Prenatal and neonatal datasets were reviewed to identify pregnancies with NTDs from 1 institution between January 2000 and December 2003. AFP screening was offered < 21 weeks and considered elevated if > or = 2.50 multiples of the median. Standard ultrasound was performed for specific indications in low-risk pregnancies. RESULTS: There were 66 NTDs, 1 per 950 deliveries. AFP sensitivity was 65%. If the gestational age used for AFP calculation was confirmed with ultrasound, sensitivity improved to 86%. The sensitivity of standard ultrasound was 100%, P < .001 compared with AFP screening. NTDs detected with standard ultrasound were identified later in gestation, as examinations were performed for other indications. CONCLUSION: Standard ultrasound improved NTD detection over AFP screening alone, by improving AFP test sensitivity and identifying NTDs in low-risk pregnancies.

Adult↗
PubMed2005

Periconceptional dietary intake of myo-inositol and neural tube defects in offspring.

BACKGROUND: Periconceptional intake of nutrients in addition to folic acid may contribute to neural tube defect (NTD) etiologies; a likely candidate is myo-inositol. We investigated whether maternal periconceptional dietary intake of myo-inositol influenced NTD risk. METHODS: Data were derived from a case-control study of fetuses and infants with NTDs among 1989-1991 California births. Interviews were conducted with mothers of 454 NTD cases and with mothers of 462 nonmalformed controls. A standard 100-item food frequency questionnaire was used to assess nutrient intake. RESULTS: We observed small increases in risk, with increases slightly more evident for anencephaly, associated with intakes of myo-inositol less than the highest intake quartile, e.g., risk of anencephaly was 1.3 (0.7-2.4) among fetuses whose mothers consumed lowest versus highest intakes of myo-inositol. These small increases, however, were imprecise, and also did not indicate increasing risk with decreasing level of myo-inositol intake. Adjusted risk estimates did not differ considerably from their unadjusted counterparts. CONCLUSIONS: Our results do not indicate that myo-inositol intake, as measured in this study, is strongly associated with risk of human NTDs.

Female↗
PubMed1983

Effect of hydroxyurea on neural tube defects in the curly-tail mouse.

Around 60% of curly-tail mice spontaneously develop neural tube defects (NTD), that is, exencephaly, and/or spina bifida (open lesions), or a curly tail (closed lesion), due to an incompletely penetrant recessive gene. Various doses of hydroxyurea, a teratogen to the rodent central nervous system, were administered to curly-tail mice on either day 8 or day 9 of pregnancy in an attempt to increase the number of NTD in the embryos. No dose used on either day achieved this. However, on day 8, the proportion of affected mice with open lesions increased from around 30% in control mice to 78% with 400 mg/kg hydroxyurea, and this was accounted for specifically by the production of exencephaly. When administered on day 9, 400, 500, and 600 mg/kg hydroxyurea (the latter two doses being lethal to embryos on day 8) actually reduced the incidence of total NTD, to around 30%. Among these affected mice, even though reduced in number, there was still a slight tendency for an increase in the number of exencephalics. Hydroxyurea also produced gastroschisis in a small percentage of embryos; the greatest incidence was 36% with 400 mg/kg on day 8.

Animals↗
PubMed1998

Maternal smoking, body mass index, and neural tube defects.

The Swedish health registries were used to investigate a possible effect on the incidence of neural tube defects (NTDs) of maternal smoking and maternal body mass index (BMI) (kg/m2). Among 1,199,701 infants born in 1983-1993 with known smoking exposure in early pregnancy, 621 infants with NTDs were selected. After controlling for year of birth, maternal age, parity, education level, BMI, and immigrant status (yes/no), a highly significant, protective effect of maternal smoking on the incidence of NTDs was found. The adjusted odds ratios (OR) and (95% confidence intervals (CI)) for maternal smoking among infants with NTDs (total), anencephaly, and spina bifida were 0.75 (0.61-0.91), 0.49 (0.28-0.85), and 0.76 (0.61-0.95), respectively. A protective dose-response effect of smoking was indicated but was not statistically significant. The association between NTDs and maternal BMI found in earlier studies was supported. Women with BMI >26.0 were found to be at higher risk of having an infant with NTD compared with women in other BMI classes (adjusted OR=1.35, 95% CI 1.00-1.83). For women with BMI > or =29, the corresponding odds ratio was 1.29 (0.81-2.05). No obvious explanation was found, either for the detected association between NTDs and BMI, or for the protective effect of maternal smoking.

Adult↗
PubMed1980

Prenatal diagnosis of neural tube defects. V. The value of amniotic fluid cholinesterase studies.

Total cholinesterase activity in amniotic fluid obtained from 150 fetuses was measured. Elevated values were found in 94% of samples from fetuses known to have neural tube defects (spina bifida, anencephaly) when compared to nonbloody samples from normal fetuses. Contamination of amniotic fluid with blood was observed to elevate total cholinesterase activity in some, but not all, such specimens. Total cholinesterase activity did not vary with gestational age between 15 and 24 weeks. These data were compared to our large alpha-fetoprotein (AFP) assay experience used for the prenatal detection of neural tube defects. We concluded that the assay of total cholinesterase activity in amniotic fluid could be a useful adjunct to the AFP assay, especially in those samples contaminated with blood.

Amniotic Fluid↗
PubMed1994

Use of local neural tube defect registers to interpret national trends.

To conduct a number of studies into the prevalence of neural tube defects (NTD) in the area covered by the Oxford Record Linkage Study (ORLS), multiple sources were used to build a local register of cases occurring in Oxfordshire and West Berkshire between 1968-1990. One source of potential cases--namely, termination and congenital malformation monitoring data available for the locality from the Office of Population Censuses and Surveys (OPCS) data--were kept separate. Comparison of the local cases recorded by OPCS and those known to the register from 1974-1990, using the method of capture-recapture, suggested that national data are only about two thirds complete, but that this underreporting is likely to be reasonably consistent from year to year. OPCS data can therefore be used to study NTD trends if not absolute risks. The local register seemed, by the same yardstick, to be very complete and is being used in a variety of studies of the occurrence of NTD. Survival to one year in this area, over the period 1968-1990, has only improved in the recent past, if at all. Most NTD pregnancies now end in termination rather than birth, and there has been a true decline in the occurrence of NTDs, and likewise the different subtypes.

Abortion, Legal↗