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PubMed2003

Review of animal models of surgically induced spinal neural tube defects: implications for fetal surgery.

Animal models have been used to help study the embryopathy and pathophysiology of neurological deterioration in open neural tube defects. Results from studies of lesion induction and defect repair in these animals have become the basis for intrauterine repair in humans. This review attempts to discern the advantages and flaws in animal models that may help us understand why spinal cord function is not preserved to the same degree in humans compared to the animal models.

Animals↗
PubMedDate not supplied

Prenatal diagnosis and elective termination of neural tube defects in Hawaii, 1986-1997.

OBJECTIVE: To determine the influence of various factors on the prenatal diagnosis and elective termination of neural tube defects (NTDs) in Hawaii in 1986-1997. METHODS: Data from a birth defects registry were analyzed and included 245 cases. RESULTS: 74% of the cases were prenatally diagnosed and 48% were terminated. Anencephaly was more likely to be prenatally diagnosed and electively terminated than spina bifida or encephalocele. Other factors such as maternal age, race/ethnicity, place of residence, and elevated maternal serum alpha-fetoprotein influenced the prenatal diagnosis and/or elective termination of NTD-affected pregnancies. However, a given factor may influence prenatal diagnosis and elective termination in different ways. CONCLUSIONS: Various diagnostic and demographic factors can influence the prenatal diagnosis and the subsequent termination of NTD-affected pregnancies.

Abortion, Induced↗
PubMed2005

Human neural tube defects: developmental biology, epidemiology, and genetics.

Birth defects (congenital anomalies) are the leading cause of death in babies under 1 year of age. Neural tube defects (NTD), with a birth incidence of approximately 1/1000 in American Caucasians, are the second most common type of birth defect after congenital heart defects. The most common presentations of NTD are spina bifida and anencephaly. The etiologies of NTDs are complex, with both genetic and environmental factors implicated. In this manuscript, we review the evidence for genetic etiology and for environmental influences, and we present current views on the developmental processes involved in human neural tube closure.

Animals↗
PubMed1986

Detection of neural tube defects with alpha-fetoprotein measurement in amniotic fluid. A protocol for managing elevated values.

The clinical efficacy of rocket immunoelectrophoresis (RIE) and radioimmunoassay (RIA) methods for the measurement of amniotic fluid alpha-fetoprotein (AFP) were compared in separate series of over 1,000 pregnancies each. Using a mean +3 SD limit, 21 of 1,414 pregnancies monitored with RIE and 21 of 1,006 monitored with RIA were interpreted as having borderline elevated values. Five of the elevated AFP values in each series represented abnormal fetuses. No neural tube defects went undetected, although one was recognized only with ultrasound. Only two of seven abnormal fetuses had a family history of neural tube defects, indicating that maternal serum AFP measurement is an important preventive measure in pregnancies that are not recognized as at high risk. The data support the use of commercially available RIA kits for amniotic fluid AFP measurement and suggest a protocol for management of elevated values.

Amniotic Fluid↗
PubMed1986

Prenatal detection of a neural tube defect after fetal exposure to valproic acid.

Fetal exposure to valproic acid has recently been associated with an increased incidence of neural tube defects. The prenatal detection of a fetus with both hydrocephalus and meningomyelocele after valproic acid exposure is presented and specific recommendations made for antepartum evaluation in future pregnancies.

Abortion, Therapeutic↗
PubMed1994

Maternal flu, fever, and the risk of neural tube defects: a population-based case-control study.

Results of clinical and epidemiologic studies have shown an increased risk for neural tube defects (NTD) in infants whose mothers were exposed to heat during pregnancy. However, the risk for NTD in infants whose mothers had influenza during pregnancy has not been well studied. This population-based case-control study of infants born in metropolitan Atlanta, Georgia, from 1968 through 1980 included 385 infants with NTD, 3,647 infants with other birth defects, and 2,676 infants without birth defects. Of the 385 mothers of case infants, 31 reported having a 2-day or longer episode of flu with fever from 1 month before through 3 months after conception (odds ratio (OR) = 3.0; 95% confidence interval (CI) 1.9-4.7). Infants of mothers who took medications for their episodes of flu with fever had an even higher risk for NTD (OR = 4.3, 95% CI 2.6-7.1). When mothers of infants with birth defects other than NTD were used as controls, an increased risk of NTD remained for flu with fever (OR = 1.7, 95% CI 1.1-2.5). There was no increased risk for NTD among the infants of mothers who reported fever from causes other than flu. Because of the heterogeneity of maternal flu, the individual contributions of infection, fever, and medications remain difficult to disentangle.

Case-Control Studies↗
PubMed2005

Folic acid and pantothenic acid protection against valproic acid-induced neural tube defects in CD-1 mice.

In utero exposure to valproic acid (VPA) during pregnancy is associated with an increased risk of neural tube defects (NTDs). Although the mechanism by which VPA mediates these effects is unknown, VPA-initiated changes in embryonic protein levels have been implicated. The objectives of this study were to investigate the effect of in utero VPA exposure on embryonic protein levels of p53, NF-kappaB, Pim-1, c-Myb, Bax, and Bcl-2 in the CD-1 mouse. We also evaluated the protective effects of folic acid and pantothenic acid on VPA-induced NTDs and VPA-induced embryonic protein changes in this model. Pregnant CD-1 mice were administered a teratogenic dose of VPA prior to neural tube closure and embryonic protein levels were analyzed. In our study, VPA (400 mg/kg)-induced NTDs (24%) and VPA-exposed embryos with an NTD showed a 2-fold increase in p53, and 4-fold decreases in NF-kappaB, Pim-1, and c-Myb protein levels compared to their phenotypically normal littermates (P<0.05). Additionally, VPA increased the ratio of embryonic Bax/Bcl-2 protein levels (P<0.05). Pretreatment of pregnant dams with either folic acid or pantothenic acid prior to VPA significantly protected against VPA-induced NTDs (P<0.05). Folic acid also reduced VPA-induced alterations in p53, NF-kappaB, Pim-1, c-Myb, and Bax/Bcl-2 protein levels, while pantothenic acid prevented VPA-induced alterations in NF-kappaB, Pim-1, and c-Myb. We hypothesize that folic acid and pantothenic acid protect CD-1 embryos from VPA-induced NTDs by independent, but not mutually exclusive mechanisms, both of which may be mediated by the prevention of VPA-induced alterations in proteins involved in neurulation.

Animals↗
PubMed1997

Elevated rates of severe neural tube defects in a high-prevalence area in northern China.

In the northern provinces of China, the birth prevalence rate of neural tube defects (NTDs) is among the highest in the world-at about 6 per 1,000 births in rural areas. A unique population-based birth defects surveillance system in which photographs are taken of infants with selected external birth defects was implemented in two provinces in northern China and two provinces in southern China where NTD rates approximate those in the United States. In the period from March 1992 through December 1993, 660 infants with NTDs were identified by the surveillance project from a birth cohort of 251,567. We compared data from the two surveillance areas in China with data from a low-prevalence area in the United States to determine if the pattern of NTD types differs. Based on birth prevalence rates of NTDs from the Metropolitan Atlanta Congenital Defects Program, the observed to expected ratios for two types of NTDs are markedly increased at 80.8 for craniorachischisis and 25.0 for iniencephaly. Rates of these two NTDs in the southern provinces are increased to a lesser degree with observed to expected ratios of 7.1 for craniorachischisis and 2.7 for iniencephaly. The pattern of NTDs in northern China shows an increase in types that are rare in low-prevalence areas such as metropolitan Atlanta. Increased awareness of varying patterns of NTDs in different populations may have important implications for identifying etiologic and pathogenetic mechanisms of NTDs.

China↗
PubMed1983

Recurrence risk of neural tube defects following a miscarriage.

Data from 280 sibships in three published series were used to see if the increased risk of neural tube defect (NTD) associated with having had a miscarriage in the immediately preceding pregnancy was also found in women with a previous affected pregnancy. A statistically significant relative risk of 4.0 (2-tail P = 0.0111, Fisher exact test) was found among such women, and this could not be accounted for by the effect of parity or of a history of miscarriage in general. The finding may be useful when counselling patients.

Abortion, Spontaneous↗
PubMed2006

Neural tube defects and maternal biomarkers of folate, homocysteine, and glutathione metabolism.

BACKGROUND: Alterations in maternal folate and homocysteine metabolism are associated with neural tube defects (NTDs). The role played by specific micronutrients and metabolites in the causal pathway leading to NTDs is not fully understood. METHODS: We conducted a case-control study to investigate the association between NTDs and maternal alterations in plasma micronutrients and metabolites in two metabolic pathways: methionine remethylation and glutathione transsulfuration. Biomarkers were measured in a population-based sample of women who had NTD-affected pregnancies (n = 43) and a control group of women who had a pregnancy unaffected by a birth defect (n = 160). We compared plasma concentrations of folate, vitamin B(12), vitamin B(6), methionine, S-adenosylmethionine (SAM), s-adenosylhomocysteine (SAH), adenosine, homocysteine, cysteine, and reduced and oxidized glutathione between cases and controls after adjusting for lifestyle and sociodemographic factors. RESULTS: Women with NTD-affected pregnancies had significantly higher plasma concentrations of SAH (29.12 vs. 23.13 nmol/liter, P = .0011), adenosine (0.323 vs. 0.255 mumol/liter; P = .0269), homocysteine (9.40 vs. 7.56 micromol/liter; P < .001), and oxidized glutathione (0.379 vs. 0.262 micromol/liter; P = .0001), but lower plasma SAM concentrations (78.99 vs. 83.16 nmol/liter; P = .0172) than controls. This metabolic profile is consistent with reduced methylation capacity and increased oxidative stress in women with affected pregnancies. CONCLUSIONS: Increased maternal oxidative stress and decreased methylation capacity may contribute to the occurrence of NTDs. Further analysis of relevant genetic and environmental factors is required to define the basis for these observed alterations.

Adult↗
PubMed1987

The impact of screening for open neural tube defects in England and Wales.

Using information derived from the voluntary system of notification of congenital malformations in England and Wales, the birth prevalence of anencephaly and spina bifida was estimated to have declined by 80 per cent from 31.5 to 6.2 per 10,000 between 1964-1972 and 1985. Over the same period, notified terminations of pregnancy with a suspected fetal central nervous system abnormality increased from less than 1 per cent to 56 per cent of neural tube defect births and central nervous system terminations combined, accounting for 31 per cent of the decline in births. Routinely collected national statistics provide a method for monitoring the impact of screening for open neural tube defects. However because they are incomplete and lack detail an alternative method of monitoring is needed. This paper includes an outline of such a method, together with the results of a pilot study designed to assess the feasibility of monitoring screening in the Oxford Region.

Amniocentesis↗
PubMed1994

A familial association between twinning and upper-neural tube defects.

An increased twinning rate has been observed in the near relatives (sibs, parents, and aunts and uncles) of probands with neural tube defects (NTDs) occurring at the level of the 11th thoracic vertebra and above (upper NTDs). The twin rate was more than double that of the near relatives of probands with lower NTDs and of those of probands with Mendelian disorders (the controls). The excess twinning was same sex and can therefore consist of either MZ or same-sex DZ twins. Furthermore, upper-NTD families with twins had a higher NTD-sibling occurrence rate than did families without twins. These findings, if corroborated, may imply an etiology common to twinning and NTDs and can perhaps be applied in counseling NTD families.

Female↗
PubMed1995

Genesis and prevention of spinal neural tube defects in the curly tail mutant mouse: involvement of retinoic acid and its nuclear receptors RAR-beta and RAR-gamma.

A role for all-trans-retinoic acid in spinal neurulation is suggested by: (1) the reciprocal domains of expression of the retinoic acid receptors RAR-beta and RAR-gamma in the region of the closed neural tube and open posterior neuropore, respectively, and (2) the preventive effect of maternally administered retinoic acid (5 mg/kg) on spinal neural tube defects in curly tail (ct/ct) mice. Using in situ hybridisation and computerised image analysis we show here that in ct/ct embryos, RAR-beta transcripts are deficient in the hindgut endoderm, a tissue whose proliferation rate is abnormal in the ct mutant, and RAR-gamma transcripts are deficient in the tail bud and posterior neuropore region. The degree of deficiency of RAR-gamma transcripts is correlated with the severity of delay of posterior neuropore closure. As early as 2 hours following RA treatment at 10 days 8 hours post coitum, i.e. well before any morphogenetic effects are detectable, RAR-beta expression is specifically upregulated in the hindgut endoderm, and the abnormal expression pattern of RAR-gamma is also altered. These results suggest that the spinal neural tube defects which characterise the curly tail phenotype may be due to interaction between the ct gene product and one or more aspects of the retinoic acid signalling pathway.

Animals↗
PubMed1996

[Serum screening in pregnant women for Down syndrome and open neural-tube defects; testing against the Health Council criteria for genetic screening].

OBJECTIVE: To check whether serum screening for Down syndrome and open neural tube defects satisfies the criteria set by the 'Committee Genetic screening' of the Dutch Health Council. DESIGN: Theoretical evaluation. METHOD: Serum screening (the combined serum assessment of alpha-fetoprotein, human chorionic gonadotrophin and unconjugated oestriol, taking into consideration maternal age) was assessed against the Dutch Health Council criteria. The absolute criteria could be subdivided into a group of general conditions not related to a particular screening programme, and a group of programme-specific conditions. RESULTS: Population serum screening satisfied some of the absolute criteria, while the programme-specific conditions should be realised in an actual screening programme. Psychological and community consequences of such a screening have not yet been investigated in the Dutch population.

Chorionic Gonadotropin↗
PubMedDate not supplied

The incidence and risk factors of neural tube defects in Izmir, Turkey: a nested case-control study.

The aim of this study was to determine the incidence of neural tube defects (NTDs) in Izmir, Turkey, and to evaluate risk factors that may be associated with NTD-affected pregnancies. A nested case-control study was carried out in all hospitals in Izmir. Controls were matched with cases on an individual basis according to the newborn's age and hospital in which they were born. There were 56 newborns with NTD out of 36,331 deliveries in Izmir hospitals in 2000. The incidence of NTD was 1.5 per 1000 births. Forty-four cases and 88 controls were analyzed for risk factors. According to chi-square analysis, maternal education, paternal education, maternal nutritional status, maternal drug usage, and presence of maternal chronic diseases and acute infections during pregnancy were found significantly different between case and control groups.

Case-Control Studies↗
PubMed1980

The recurrence risk for neural tube defects in the United States: a collaborative study.

To determine the recurrence risk for patients with one prior pregnancy affected with neural tube defects (NTD), the authors have pooled data from eight testing centers. In 831 pregnancies studied because one sib was affected with an NTD, the recurrence rate was 3.0%, with 95% confidence limits of 2.0-4.3%, and 99% confidence limits of 1.8-4.8%. The recurrent lesion, whether spina bifida or anencephaly, tended to be concordant with the first to a significant degree. Only 12.2% of recurrent NTD were different from the first, with 95% confidence limits of 4.1-26.2%, and 99% confidence limits of 1.7-30.9%. Both an accurate recurrence risk and the information that a recurrent NTD lesions tends to be concordant with that in the first affected child are useful in the genetic counseling of patients in the United States and in the selection of appropriate prenatal diagnostic studies.

Female↗
PubMed1995

Maternal-fetal folate status and neural tube defects: a case control study.

The object of this study was to explore the role of folate in the pathophysiology of neural tube defects (NTD). Maternal and fetal serum and red blood cell folate were assayed in 14 cases of NTDs and compared with 14 controls with other malformations and matched for gestational age (range 18-36 weeks). In mothers of NTD fetuses, serum folate (5.2 ng/ml), red blood cell folate (294 ng/ml) and the folate methylation rate (65%) were significantly lower than in controls (6.6 and 399 ng/ml, respectively, and 77%). However, the fetal folate status was similar in cases and controls. In the NTD group, folate metabolism was altered in the mothers but not in the fetuses. Therefore, a normal folate placental transfer can be assumed in this group. In addition, it could be speculated that decreased maternal folate methylation might be involved in the pathogenesis of NTDs.

Case-Control Studies↗
PubMed2005

An exploration of health effects of folic acid in pregnancy beyond reducing neural tube defects.

OBJECTIVES: First, to examine the biological basis of why folic acid may have health effects beyond its proven effect of reducing neural tube defects; and second, to explore current controversial policies of folic acid supplementation and food fortification. METHODS: We searched MEDLINE for English-language papers published from 1991 to 2003, using the key words "folic acid" and "folate." The literature search was restricted to human studies. Of 8986 publications identified, 65 were relevant to the objectives of this paper. RESULTS: Analysis of the literature revealed that a major mechanism of folic acid in improving infant health may be related to its effect in correcting maternal folate-homocysteine-methylenetetrahydrofolate reductase metabolic defects. Conversely, exposure to high levels of folic acid may have such adverse health effects as increased risk of neurologic disorders in the general population. CONCLUSIONS: Randomized trials or well-designed prospective cohort studies are needed to assess the effects of folic acid on various pregnancy outcomes. To enable an examination of the association between folic acid and rare outcomes, such as a specific category of birth defects and fetal and neonatal deaths, it is necessary to recruit a large number of pregnant women to participate in such studies.

Dietary Supplements↗