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PubMed1996

Hispanic origin and neural tube defects in Houston/Harris County, Texas. I. Descriptive epidemiology.

High prevalences of anencephaly and neural tube defects (NTDs) have recently been recorded for several Texas counties bordering Mexico. In addition, a few investigators have reported Hispanics to be at elevated risk for NTDs (anencephaly and spina bifida). Factors contributing to this risk have not been established. The authors conducted a study of NTDs in Harris County, Texas, to determine the prevalence of each defect. Prevalence was established by identifying cases among resident live births and fetal deaths (stillbirths at > or = 20 weeks) occurring from April 1, 1989, through December 31, 1991. Using multiple case ascertainment methods, 59 cases of anencephaly and 32 cases of spina bifida were detected, resulting in prevalences of 3.8 (95% confidence interval 2.9-4.9) and 2.0 (95% confidence interval 1.4-2.8) per 10,000 live births, respectively. The ratio of anencephaly prevalence to spina bifida prevalence was 2:1 in 1989, 1:1 in 1990, and 3:1 in 1991, with a significant difference in 1991. The female:male prevalence ratio was 1.0 for spina bifida and 2.2 for anencephaly, and was higher still for anencephaly among non-Hispanics (prevalence ratio = 5.6). For each defect, Hispanics experienced a prevalence approximately three times that of non-Hispanics. This ethnic difference was greater for males with anencephaly and for females with spina bifida. For anencephaly, the Hispanic:white/Anglo prevalence ratio (4.2) and the African-American:white/Anglo prevalence ratio (1.9) were greatly elevated and the Hispanic:African-American prevalence ratio (2.2) was similar, relative to comparable studies from the past two decades. The prevalence of anencephaly recorded for public hospitals (7.0 per 10,000) was three times greater than that for private hospitals (2.4 per 10,000). Spina bifida figures were similar for public (prevalence = 2.2 per 10,000) and private (prevalence = 2.0 per 10,000) hospitals. A significantly higher prevalence of both defects was documented among Hispanics in Harris County. The higher anencephaly rates among Hispanics, African-Americans, and those using public hospitals in an era of NTD screening, prenatal diagnosis, and elective pregnancy termination suggest that socioeconomic and perhaps cultural/religious factors might influence the recorded birth prevalence of this defect in particular groups.

Anencephaly↗

PubMed1999

Lipoic acid prevention of neural tube defects in offspring of rats with streptozocin-induced diabetes.

OBJECTIVE: Increased oxidant stress has been suggested to play a role in the pathogenesis of disturbed embryogenesis in diabetic pregnancies. The present study was conducted to determine whether administration of lipoic acid, a naturally occurring antioxidant, would reduce the incidence of diabetic embryopathy in the streptozocin-induced diabetic rat model. STUDY DESIGN: After conception, rats were randomly distributed to 5 groups. From day 1, rats were daily injected intraperitoneally with either lipoic acid, 30 mg/kg, or vehicle. At day 6, rats from groups 3, 4, and 5 were made diabetic by a single intraperitoneal injection of streptozocin. Group 4 rats were injected with lipoic acid from day 1 to day 6, after vehicle treatment until day 17. At day 17 of gestation, rats were killed. The fetuses were released from the yolk sacs and surrounding decidua and were examined for size, resorption rate, and neural tube defects. RESULTS: Pregnant diabetic rats treated with vehicle lost weight during pregnancy (-3.2 +/- 1.9 g/d), as opposed to normal pregnancy-related weight gain (3.5 +/- 0.5 g/d). Treatment with lipoic acid protected against diabetes-induced weight loss, without a measurable effect on fed-state glucose concentrations. Daily treatment with lipoic acid (pregnancy days 1 to 17) was efficient in reducing the resorption rate from 24.0% +/- 9.5% in vehicle-treated diabetic rats to 10.2% +/- 4.8% in lipoic acid-treated diabetic rats (P <.05). The rate of neural tube defects in diabetic rats treated with lipoic acid throughout the pregnancy was reduced from 26.0% +/- 7.0% to 10.2% +/- 3.2% (P <.05). In rats treated only during pregnancy days 1 to 5 (before diabetes induction), lipoic acid failed to exert its protective effects against neural tube defects, which emphasizes the importance of the presence of lipoic acid during the organogenesis period. The atherosis of placental vasculature demonstrated in the vehicle-treated diabetic rats was absent from placentas obtained from lipoic acid-treated diabetic animals. CONCLUSIONS: Our data demonstrate a protective effect of lipoic acid against diabetic embryopathy, fetal losses, and ultrastructural alteration of diabetic placentas.

Animals↗

PubMed1994

Spontaneous abortion--high risk factor for neural tube defects in subsequent pregnancy.

An increased spontaneous abortion rate has been observed in pregnancies preceding that of fetuses or newborn infants with neural tube defects (NTDs). There are 2 suggested explanations for this observation. One is that a trophoblastic cell rest, remaining from a previous aborted pregnancy, interferes with normal embryogenesis. The second is that the previous lost fetus was affected with NTD. We studied the obstetric history of mothers of newborn infants with NTDs compared to those with other birth defects, in low and high risk groups for NTD (Jew and Bedouins). A significantly higher spontaneous abortion rate (48%) in the preceding pregnancy was found in the NTD group compared to the group with other birth defects (20%). This was especially remarkable for spina bifida cases in the Jewish study population. A significantly higher rate of preceding spontaneous abortion was also found in congenital heart defects (CHD) when compared to other congenital malformations. A hypothesis based on the multifactorial threshold model is put forward to explain these findings. Based on the realization that spontaneous abortion constitutes a high risk factor for NTD and possibly also CHD, we recommend a delay of subsequent pregnancy and periconceptional treatment with folic acid following spontaneous abortion.

Abortion, Spontaneous↗

PubMed2001

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.

Alleles↗

PubMed1993

Prenatal screening for neural tube defects, quality specification of maternal serum alphafetoprotein analysis.

The bimodal approach for quality specification in prenatal screening for neural tube defects has been used. The method for assessing specifications has been the expenses for the society. It has been shown that the cut-off values and analytical bias are of importance. It is recommended to use a reference serum for local calibration to keep the level within defined limits when changing to a new batch of reagents.

Female↗

PubMed2001

[Clinical epidemiological study of neural tube defects classified according to the five sites of closure].

OBJECTIVES: To identify the frequency at birth of neural tube defects (NTD) in the Spanish population. NTDs were considered as a whole as well as according to the different sites of closure failure, following the theory of multisite closure of the neural tube. To analyze the epidemiological characteristics of the different sites. METHODS: Data derived from the Spanish Collaborative Study of Congenital Malformations (ECEMC), from April 1976 to March 1995. Among the 1,222,698 live births during this period, 784 infants had NTD were controlled. Among these, 784 infants had NTD. RESULTS: The prevalence of NTD in our population was 1.01 per 1,000 births, a frequency which is considered medium-to low. Only 5.74% of the NTD were of known etiology: 2.17% were genic, 1.27% were chromosomic and 2.29% were environmental. Excluding NTD of genetic etiology, whether genic or chromosomic, most of the remaining were isolated defects (multifactorial) and 16.78% multiple malformations. Site 1, where the closure of the neural tube starts, represented 24% of all the affected sites. However, more than 50% of the NTDs corresponded to closure failure at the junction of two sites. CONCLUSIONS: As in other populations with a low prevalence of NTD at birth, the prevalence of these defects in our population showed a trend to decrease with time, due to the possibility of interrupting gestation after prenatal diagnosis. All the NTD could be classified according to the theory of multisite closure of the neural tube, including 13 cases with several noncontiguous affected sites. Two types of NTD were observed: in the first, closure failed to occur and in the second, two closures failed to meet.

Anencephaly↗

PubMed1980

Women's attitudes to screening for neural tube defects.

The attitudes of 2254 pregnant and 262 other women to serum alpha-fetoprotein (AFP) screening for neural tube defects (NTDs) were investigated, the former by interview and the latter by questionnaires to which 228 replies were received. Over 97 per cent of the pregnant women wanted to be included in such a screening programme. Ninety-six per cent of other women who completed the questionnaire were in favour of national screening for NTDs but 14 per cent of them were uncertain about the action they would take if the test were positive.

Abortion, Induced↗

PubMed2002

The curly-tail (ct) mouse, an animal model of neural tube defects, displays altered homocysteine metabolism without folate responsiveness or a defect in Mthfr.

Maternal mild hyperhomocysteinemia is associated with increased risk for bearing children with neural tube defects (NTD). Folate intake corrects hyperhomocysteinemia and prevents up to 70% of NTD. The curly-tail (ct) mouse, an animal model for NTD, has been suggested to display features that closely resemble the human defect. We therefore investigated folate metabolism in ct mice. On control and folate-/choline-deficient diets, ct mice exhibited higher plasma homocysteine levels than control C57Bl/6 mice. This increase was associated with increased liver S-Adenosylhomocysteine and decreased S-adenosylmethionine:S-adenosylhomocysteine (SAM/SAH) ratios. Since the ct locus maps in close proximity to the gene for methylenetetrahydrofolate reductase (Mthfr), a modifier of homocysteine levels in man, we also assayed Mthfr activity and sequenced the 5(') regulatory region; these experiments suggested that Mthfr is not defective in the ct strain. Finally, we examined the influence of dietary folate on NTD incidence in the ct strain, but did not identify significant differences among the four diets used in the study. Our work suggests that altered homocysteine metabolism may contribute to the pathogenetic mechanism of the ct defect, but, unlike human NTD, nutritional or genetic deficiencies in folate metabolism do not appear to play a significant direct role.

5' Flanking Region↗

PubMed2004

Folic acid in the prevention of neural tube defect--a programme for Malaysia?

There is good evidence that folic acid is safe and efficacious for reducing neural tube defect (NTD). All women capable of becoming pregnant should take 400 microgram daily. This can be given in the form of a daily vitamin supplement, by food fortification, or by increasing natural dietary folates. Compulsory grain fortification has been shown to reduce NTD in a population but supplementation and dietary advice have not. Malaysia should work towards a programme of grain fortification and use alternative strategies to reach sections of the population that would not be covered but several research questions need to be answered before a programme could be implemented in Malaysia.

Female↗

PubMed1991

Maternal hair zinc concentration in neural tube defects in Turkey.

Hair zinc concentration was measured in samples taken from 57 mothers who delivered infants with neural tube defects (NTD) (mainly anencephaly). Control groups consisted of 30 healthy mothers with normal offspring and 37 nonpregnant women from middle-income backgrounds. Zinc concentration was also measured in the hair of eight infants with NTD (four being anencephalic). The mean maternal hair zinc concentration in the NTD group (128.2 +/- 38.9 micrograms/g) was lower than that of the control women (p less than 0.001), whereas the mean hair zinc level of malformed babies (250.4 +/- 85.2 micrograms/g) was significantly higher than that of normal infants (193.4 +/- 39.2 micrograms/g) (p less than 0.05). Maternal nutritional zinc deficiency was thought to be one of the factors responsible for NTD in Turkey.

Adolescent↗

PubMed1990

Familial clustering of neural tube defects and gastric cancer.

A retrospective cohort study was conducted to determine whether producing an offspring with a neural tube defect (NTD) is associated with the development of unusual patterns of cancer among the parents in subsequent years. Mothers and fathers who had a child with an NTD in Upstate New York from 1945 to 1955 were followed through 1979 and compared to a control group of parents with normal offspring. Overall mortality and site-specific cancer incidence were not significantly different for case parents versus control parents, with the exception of gastric cancer, which occurred significantly more frequently in case parents. The finding of a familial association between NTDs and gastric cancer, coupled with a parallel decline in rates of these two diseases, suggests a common aetiology, perhaps related to dietary factors.

Adult↗

PubMed1988

Amniotic fluid cholinesterase of valproate-induced exencephaly in the mouse: an animal model for prenatal diagnosis of neural tube defects.

After a single administration of the antiepileptic drug valproic acid (VPA; i.p.:600 mg/kg) on day 8 of gestation in the mouse embryotoxicity and amniotic fluid (AF) cholinesterase (ChE) were evaluated on day 16 of gestation. VPA treatment induced an increase in embryolethality, neural tube defects (exencephaly), cleft palate, deformed vertebrae, open eyes, and a reduction in fetal weight. In VPA-exposed fetuses AF total ChE (TChE) activity of exencephalic fetuses was higher than that of normal fetuses. However, in 3 out of 110 normal fetuses of the control group TChE activity was found in the AF. There was no correlation between blood contamination of AF and its TChE activity, either in non-exencephalic control or treated embryos. Using ethopropazine as a "pseudo"-ChE inhibitor in vitro, the percentage of acetyl-ChE in blood-contaminated AF was similar to that of fetal rather than maternal serum, indicating that AF was contaminated with fetal and not with maternal blood. VPA-induced exencephaly in mice may provide an animal model to further investigate biochemical markers for prenatal diagnosis of neural tube defects.

Amniotic Fluid↗

PubMed1986

Monitoring performance in the NHS. The district neural tube defect screening service.

A small medical school team has developed a six item system (SIS) for monitoring the neural tube defect (NTD) screening service. SIS is discussed in relation to possible alternative monitoring systems and the advantages which led to its implementation are described. In July 1982 the system was introduced in three districts in South Wales and the first year's results are presented. These permit the local provision, written policies and clinical and management responsibility of the service to be examined and deficiencies in the relevant information systems to be identified. Of particular concern is the discovery that districts have no way of knowing the number of terminations for NTD, and thus their current NTD incidence. In view of these findings, it would seem advisable for all districts providing NTD screening to monitor their service. SIS provides a simple, cheap and effective monitoring system which could be easily implemented throughout England and Wales.

Diagnostic Tests, Routine↗

PubMed1985

Reduction in the frequency of neural tube defects in splotch mice by retinoic acid.

In the homozygous state, the splotch (Sp) gene causes spina bifida and exencephaly. Close to 25% of the embryos from Sp/ + X Sp/+ litters are affected. The frequency of these defects is significantly reduced by maternal treatment with 5 mg/kg retinoic acid on day 9 of gestation. There is no significant increase in the resorption frequency with this treatment, indicating that the fall in the frequency of neural tube defects is not due to differential mortality of the affected fetuses. The effects of retinoic acid are time specific, with treatment at different times on day 9 having the greatest influence on either the anterior or posterior neuropore. Treatment on day 8 with the same dose of retinoic acid causes an increase in both resorptions and neural tube defects, although only the increase in the former was significant.

Animals↗

PubMed2003

[The epidemiology of neural tube defects in high-prevalence and low-prevalence areas of China].

OBJECTIVE: To describe the epidemiology of neural tube defects (NTDs) in high- and low-prevalence areas of China. METHODS: Birth defects surveillance data, collected from 1992 through 1994 was analyzed. These data were collected as part of the Sino-American cooperative project on NTDs prevention. We classified NTDs as anencephaly, encephalocele, high-level and low-level spina bifida (SB) according to location of the lesion (high vs low) and whether the defect was isolated or occurred in association with other birth defects. Rates were compared in the high-prevalence (North) region and the low-prevalence (South) region, after adjusted for classification, urban and rural, season and sex, and calculated the adjusted rate of NTDs. RESULTS: Among seven hundred and eighty-four NTDs cases in 326 874 recorded births (include in livebirth, stillbirth and fetal death with a gestational age of at least 20 weeks), the overall NTDs prevalence in the North was 5.57/1,000 births, and in the South was 0.88/1 000. There were also significant differences in the prevalence of anencephaly, encephalocele, high-level and low-level SB between North (0.97, 0.49, 2.75 and 1.11/1,000 birth) and South (0.36, 0.15, 0.21 and 0.14/1,000 birth) (P < 0.01), with adjusted prevalences in the North 3 - 7 times higher than those in the South. There were significant difference between urban (2.04) and rural areas (6.57/1,000 birth) in the North (P < 0.01), urban (0.52) and rural areas (0.95/1,000 birth) in the South (P < 0.05). Adjusted prevalence rates in the rural were 3 - 4 times higher than those of urban in the North and 1.6 - 1.9 times higher than in the South; The seasonal rate of high-level SB increased between September and November in the North (3.44/1,000 birth), while the seasonal rate of anencephaly decreased between September and November (0.18/1,000 birth) in the South. However there were no seasonal changes in other classified NTDs both in the South and North. CONCLUSIONS: The birth prevalence of NTDs in the North of China was the highest in the world. There were significant differences between the North and the South, urban and rural. There was seasonal change in high-level SB in the North, which was in accordance to the phenotype of NTDs. It was suggested that there might exist etiological heterogeneity among anecephalus, low- and high-level SB.

China↗

PubMed1996

[Syndromes with neural tube defects: epidemiologic analysis in Spain].

OBJECTIVE: We present, from an epidemiological perspective, the analysis of syndromes which present neural tube defects (NTD). Although there are many epidemiological studies on NTD all over the world, most of them are on isolated NTD; that is, when the infant only has NTD as the only anomaly. PATIENTS AND METHODS: The methodology is based on the review of hospital records of infants with congenital anomalies. This permitted the analysis of the prevalence. RESULTS: The results show that the frequency of syndromes with NTD is 27.5 time higher among stillborn infants than among liveborn infants. Nevertheless, there are not many syndromes in which the NTD are present more or less frequently. In fact, only 1.93% of the total cases with syndromes presented NTD, with the majority (43.4%) with genetic etiology. We also analyze the specific types of syndromes with NTD.

Fetal Death↗

PubMed1992

Long term effects of periconceptional multivitamin supplements for prevention of neural tube defects: a seven to 10 year follow up.

Periconceptional supplementation with Pregnavite Forte F was offered to women who presented consecutively to the Oxford genetic counselling service in the early 1980s who had previously had one or more pregnancies complicated by a neural tube defect. The first 100 children born alive to these women are the subject of this study. Birth weight, gestation, and congenital abnormalities were recorded. At age 2-5 years all 96 children remaining in the United Kingdom were assessed clinically and developmentally and behavioural information was obtained by questionnaire. At age 7-10 years, follow up of 91 children by telephone and postal questionnaire yielded further information about growth, general health, vision, hearing, and educational and behavioural status. Entry criteria excluded single mothers but the social class distribution of the sample was otherwise representative of the Oxfordshire population. There were no recurrences of neural tube defects. One child had radiological evidence of spina bifida occulta affecting only the fifth lumbar vertebra. One had an autosomal recessive disorder. Eight had random minor congenital anomalies. Birth weight for gestational age was significantly greater than for the local population and at age 7-10 years the girls were considerably taller than expected. Health, auditory, visual, and developmental status were no different from the general population. None of the children had special educational needs. None showed a major behaviour disorder but worries, fussiness, and fearfulness were highly significantly over represented.

Adult↗

PubMed2003

Periconceptional folic acid use and the prevalence of neural tube defects in The Netherlands.

OBJECTIVE: To study the effect of increased folic acid intake on the prevalence of neural tube defects (NTD) in The Netherlands. STUDY DESIGN: Using the capture-recapture method, the prevalence of NTD was estimated on the basis of five different registries on births affected by NTD. RESULTS: Total prevalence over the 1988-1998 period varied between 1.43 and 1.96 per 1000 live and still births. No decrease in total prevalence was found to have taken place during that period. Scrutiny of the last 2 years, 1997 and 1998, in which increased folic acid intake might be expected to have had an effect, did not give any indication that the prevalence of NTD was falling. CONCLUSIONS: A decrease in the Dutch prevalence of NTD during the study period could not be demonstrated due to the relatively small number of women using folic acid periconceptionally. This does not mean automatically that periconceptional folic acid use is ineffective in reducing the Dutch prevalence of NTD. Further monitoring is needed.

Dietary Supplements↗