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PubMedDate not supplied

Lack of serologic evidence for an association between Cache Valley Virus infection and anencephaly and other neural tube defects in Texas.

We tested the hypothesis that Cache Valley Virus (CVV), an endemic North American bunyavirus, may be involved in the pathogenesis of human neural tube defects. This investigation followed a 1990 and 1991 south Texas outbreak of neural tube defects with a high prevalence of anencephaly and the demonstration in 1987 that in utero infection by CVV was the cause of outbreaks of central nervous system and musculoskeletal defects in North American ruminants. Sera from 74 women who gave birth to infants with neural tube defects in south Texas from 1993 through early 1995 were tested for CVV neutralizing antibody. All tested sera did not neutralize CVV. These data suggest that CVV is not involved in the induction of human neural tube defects during nonepidemic periods but do not preclude CVV involvement during epidemics. Other endemic bunyaviruses may still be involved in the pathogenesis of neural tube defects or other congenital central nervous system or musculoskeletal malformations.

Anencephaly↗

PubMedDate not supplied

Analysis of MTHFR 1298A>C in addition to MTHFR 677C>T polymorphism as a risk factor for neural tube defects in the Turkish population.

Maternal folic acid intake in the periconceptional period is strongly related to reduction in recurrence and occurrence of birth defects involving the neural tube. Among the single nucleotide polymorphisms (SNPs) influencing the folate metabolism, the methylenetetrahydrofolate reductase (MTHFR) gene has been the one most exclusively studied. Many studies have reported significant association between MTHFR 677C>T and increased risk of neural tube defects (NTDs). Our previous study did not support this observation. The present study aimed to determine the prevalence of 1298A>C polymorphism in addition to 677C>T in the same Turkish population as a risk factor for NTDs. We genotyped case (95 offspring with NTDs, 80 mothers, 72 fathers) and control (93 healthy children) populations for MTHFR 677C>T and MTHFR 1298 A>C polymorphisms. The comparison demonstrated a significant increase in the 1298AA/677TT genotype frequency among mothers of offspring with NTDs (OR 5.23 [1.06-25.9]; p=0.067). The 677CT genotype was only 1.35 times higher than controls among mothers when 677C>T polymorphism was evaluated alone, while 677CT/1298AC in the current study demonstrated a 3.8 times increase in this risk. These observations led us to conclude that although not statistically significant, MTHFR 1298AC polymorphism might be a risk factor for the occurrence of NTDs in the Turkish population.

Adult↗

PubMed1978

Amniography in the prenatal diagnosis of neural tube defects.

Amniography for the visualization and confirmation of suspected neural tube defect was performed in 9 midtrimester gravidas. In all cases, amniotic fluid alpha-feto protein (AFP) was abnormally elevated. Four cases of anencephaly and one of spina bifida were demonstrated by amniography. These pregnancies were terminated and the defects were confirmed by gross pathologic examination. In 4 remaining cases, amniography was normal. Three of these pregnancies proceeded to term, culminating in the birth of a normal child. The fourth patient had spontaneous abortion of a normal fetus at 23 weeks of gestation. The experience reported here suggests that amniography is an important adjunctive diagnostic technique in the prenatal diagnosis of neural tube defect, and if used correctly, may significantly reduce the chance of false-positive diagnosis.

Adult↗

PubMed2005

Pax1/E2a double-mutant mice develop non-lethal neural tube defects that resemble human malformations.

Many mouse models exist for neural tube defects (NTDs), but only few of them are relevant for human patients that are born alive with spina bifida aperta. NTDs in humans show a complex inheritance, which most likely result from the involvement of a variety of predisposing genetic and environmental factors. Hints toward the identity of predisposing genetic factors for human NTDs could come from mouse studies on the development of the neural tube and spinal cord, as well as from studies on associated features of this type of diseases. Among such features is the observation that pregnancies affected by a neural tube defect frequently show changes in thymus morphology, and in both neonatal and maternal T-cell repertoire. The genes for E2a and Pax1 have both been implicated in not only paraxial mesodermal development, but also in that of the immune system. Moreover, Pax1 mutant mice have been shown to display NTDs in digenic mouse models. In the present study we have investigated the phenotype of E2a null mutant mice that are also heterozygous for the so-called undulated mutation in Pax1. Here we report that such double-mutant mice develop a non-lethal NTD that strongly resembles the classic human NTD: spina bifida aperta, associated with defects of the axial skeleton, immune system and urinary tract.

Animals↗

PubMed2000

Genetic and embryological approaches to studies of neural tube defects: a critical review. NTD Collaborative Group.

Experimental embryological models have suggested that the morphology and quantity of neural tube defects may be governed by their position along the anteroposterior axis of the embryo. Inductive interactions and genetic regulation during axis development may play a role in the patterning of neural tube defects. A major challenge in the study of human neural tube defects is determining whether the spectrum of developmental neural tube anomalies found in individuals and their families mirror experimental models and are regulated by similar processes. We have found that the various neural tube defect phenotypes can be clustered according to their position along the anteroposterior axis. The findings correlate well to the pattern of early genes expression, inductive models of the embryonic axis, and mutant NTD animal models. We suggest that NTD should be studied by their location along the anteroposterior axis and that specific mutant genes may be identified by the observed pattern of NTD in an individual or a family.

Animals↗

PubMed2000

Dietary folate and the prevalence of neural tube defects in the British Isles: the past two decades.

OBJECTIVES: To measure the changes in folate consumption and the prevalence of neural tube defects in the British and Irish populations during the past two decades. DESIGN: Ecological study. MAIN OUTCOME MEASURES: Average daily dietary folate consumption for Britain for the period 1980-1996 was estimated from the National Food Survey. Annual neural tube defect prevalences for the same period were obtained from the Oxford Record Linkage Study Neural Tube Defect register, the Glasgow EUROCAT register, and the three Irish EUROCAT registers (Belfast, Dublin and Galway). RESULTS: Dietary folate consumption increased on average by 1.6% per annum in Scotland and 1.4% in England during the study period. The annual rate of decline of neural tube defect prevalence averaged 10.4% in the Irish population, 8.2% in Glasgow, and 5.2% in Oxfordshire and West Berkshire. CONCLUSIONS: The decline in neural tube defect prevalence observed in all British and Irish populations since the early 1970s continued with the introduction of folate fortification of cereals, which produced measurable increases in average daily folate consumption. Further declines in neural tube defect prevalence may be achieved by targeted folate supplementation during the periconceptual period.

Diet↗

PubMed2001

Effects of hyperinsulinemia and obesity on risk of neural tube defects among Mexican Americans.

Although both maternal obesity and diabetes mellitus increase the risk for neural tube defects, it is unknown whether they are independent risk factors or manifestations of an underlying prediabetic state such as hyperinsulinemia. We investigated whether hyperinsulinemia was a risk factor for neural tube defects independent of obesity and hyperglycemia in Mexican-American women. We identified case and control women from residents delivering or terminating pregnancies in hospitals or birthing centers in any of the 14 Texas-Mexico border counties during 1995-2000. Case women had a pregnancy affected by anencephaly, spina bifida, or encephalocele; randomly selected control women had normal births, frequency matched by year and birth facility. Questionnaire and laboratory values obtained 5-6 weeks postpartum were available for 149 case and 178 control women. Both hyperinsulinemia and obesity were related to increased neural tube defect risk [odds ratio (OR) = 1.91, 95% confidence interval (CI) = 1.21-3.01 and OR = 1.73, 95% CI = 1.03-2.92, respectively]. Adjustment for obesity only slightly reduced the effect of hyperinsulinemia (OR = 1.75, 95% CI = 1.09-2.82). Alternatively, a modest effect remained for obesity after adjustment for hyperinsulinemia (OR = 1.45, 95% CI = 0.84-2.51). Hyperinsulinemia is a strong risk factor for neural tube defects and may be the driving force for the observed risk in obese women.

Adult↗

PubMed1991

Ultrasound detection of neural tube defects in patients with elevated maternal serum alpha-fetoprotein.

We conducted this study to determine the accuracy of ultrasound in the prenatal diagnosis of neural tube defects in women with elevated maternal serum alpha-fetoprotein (MSAFP). Among 905 pregnancies, 49 neural tube defects were correctly diagnosed by ultrasound alone; one was not. Ultrasound scanning had 98% sensitivity and 100% specificity for the detection of neural tube defects. The predictive value of a positive ultrasound diagnosis was 100% and of a negative ultrasound 99.9% for neural tube defects. Forty-three other structural abnormalities were also detected in patients with elevated MSAFP, including 19 abdominal wall defects, seven chromosomal abnormalities, five urinary tract abnormalities, one cardiac abnormality, and 11 others. Two chromosomal abnormalities were not detected. We suggest that ultrasound can be used reliably to detect neural tube defects, thereby avoiding the risks of amniocentesis.

Female↗

PubMed2000

Neural tube defects in Victoria, Australia: potential contributing factors and public health implications.

OBJECTIVES: To measure population prevalence and determine potential predictors of neural tube defects. METHOD: Analysis of all births reported to a mandated collection of perinatal data, and terminations prior to 20 weeks' gestation that have been reported to a data collection of birth defects in Victoria from 1983 to 1997. Prevalence at birth and risk ratios of infant and maternal characteristics associated with neural tube defects were calculated. RESULTS: Prevalence of spina bifida has remained steady for 15 years and was 8.8/10,000 in 1997. Anencephaly increased to 7.9/10,000 in 1997. After exclusion of pregnancy terminations, the 1997 birth prevalence was 4.5/10,000 for spina bifida and 2.4/10,000 for anencephaly. Neural tube defects are identified in 1 in 1600 fetuses, the risk being significantly higher for epileptic women (Adjusted Odds Ratio (AOR) = 3.70, 95% CI 2.25-6.07), multiple births (AOR = 4.56, 95% CI 3.46-6.02), teenage mothers (AOR = 1.47, 95% CI 1.09-2.00) compared with those aged 25-29, and women with three or more previous pregnancies (AOR = 1.40, 95% CI 1.10-1.78). The risk was lower for women of East Asian (AOR = 0.70, 95% CI 0.49-1.00) and Middle Eastern origin (AOR = 0.60, 95% CI 0.35-1.02) and these differences were approaching statistical significance. CONCLUSION: Total prevalence of neural tube defects did not decline up to 1997. IMPLICATIONS: It is unlikely that targeting 'at risk' groups identified in this study would make a difference to neural tube defect incidence. However, consideration could be given to identifying larger 'at risk' groups such as those with homocysteine metabolism defects.

Confidence Intervals↗

PubMed1995

Cytogenetics of the tissue involved in neural tube defects.

Cytogenetic techniques were used to study the tissue involved in neural tube defects. Eighteen patients have been evaluated and no specific alterations have been detected. We conclude that, whatever are the mechanisms that lead to neural tube defect, their origins must be searched for at the molecular level.

Adolescent↗

PubMed1996

Prenatal maternal dried blood screening with alpha-fetoprotein and free beta-human chorionic gonadotropin for open neural tube defect and Down syndrome.

OBJECTIVE: Our purpose was to evaluate second-trimester prenatal screening for open neural tube defects and Down syndrome by use of dried blood specimen collection and transport. STUDY DESIGN: A prospective study of 7497 dried blood specimens from patients <35 years old was performed. Specimens were assayed for maternal blood alpha-fetoprotein and free beta-human chorionic gonadotropin. Patient-specific risks for both disorders were calculated and used to determine whether further evaluation was indicated. The study included an evaluation of the median and SD of analyte multiple of the median levels. RESULTS: The initial positive rate for open neural tube defect was 4.4% adjusted to 2.7% after ultrasonographic revision and collection of a second sample. The initial positive rate for Down syndrome was 3.6% adjusted to 2.8% after ultrasonographic revision. All seven cases of open neural tube defect were detected within the increased risk group. Six of 8 (75%) cases of Down syndrome were detected. The median alpha-fetoprotein multiple of the median was 3.5 in open neural tube defect cases and 0.6 in Down syndrome cases. The median free beta-human chorionic gonadotropin multiple of the median was 2.4 in Down syndrome cases. The SD (log e) of alpha- fetoprotein and free beta-human chorionic gonadotropin in 5868 unaffected white patients was 0.4022 and 0.5635, respectively. CONCLUSION: Second-trimester dried blood screening for open neural tube defects and Down syndrome can achieve screening efficiency comparable to serum-based protocols with distinct advantages over the conventional method of blood collection.

Adult↗

PubMed2005

[Effects of public initiatives aimed at reducing neural tube defects with folic acid supplementation].

BACKGROUND: In order to prevent neural tube defects, a daily supplement of 400 microg (microgram) folic acid has been recommended in Norway since 1998, during the last month before conception and the first two or three months of pregnancy. Compliance with and effects of this recommendation has recently been evaluated in Norway in a report to the Directorate of Health and Social Welfare. MATERIAL AND METHODS: Reports published on periconceptional folic acid intake in Norway and some other countries from 1998 to autumn 2003 have been evaluated. RESULTS: In spite of several information activities, few Norwegian women start folic acid supplementation before verified pregnancy. The supplementation is started too late for the prevention of neural tube defects. A reduction is not observed in Norway. Internationally, information has not proven effective either, whereas compulsory fortification of foods with folic acid has been associated with reduced incidence. Information about periconceptional folic acid intake should be intensified. Compulsory fortification of foods with folic acid will affect the whole population, not only the target group of fertile women. If ongoing large intervention studies show improved clinical prognosis for patients with cardiovascular disease, this will be an additional argument for fortification of foods.

Female↗

PubMed2002

Polymorphic susceptibility to the molecular causes of neural tube defects during diabetic embryopathy.

Previously, we demonstrated that neural tube defects (NTDs) are significantly increased in a mouse model of diabetic pregnancy. In addition, expression of Pax-3, a gene encoding a transcription factor required for neural tube development, is significantly decreased. This suggests that diabetic embryopathy results from impaired expression of genes regulating essential morphogenetic processes. Here, we report that in one mouse strain, C57Bl/6J, embryos are resistant to the effects of maternal diabetes on NTDs and Pax-3 expression, in contrast to a susceptible strain, FVB, in which maternal diabetes significantly increases NTDs (P = 0.02) and inhibits Pax-3 expression (P = 0.01). Resistance to NTDs caused by diabetic pregnancy is a dominant trait, as demonstrated by heterozygous embryos of diabetic or nondiabetic mothers of either strain. There was no significant difference between strains in expression of genes that regulate free radical scavenging pathways, suggesting that susceptibility to oxidative stress does not account for the genetic differences. Understanding the genetic bases for differential susceptibility to altered gene expression and NTDs in diabetic mice may be important in delineating the mechanisms by which maternal hyperglycemia interferes with embryo gene expression. Moreover, if susceptibility to diabetic embryopathy is variable in humans as well as in mice, it may be possible to screen individuals at increased risk for this complication of diabetes.

Animals↗

PubMed1995

Prenatal ultrasound detection of isolated neural tube defects: is cytogenetic evaluation warranted?

OBJECTIVE: To determine the value of cytogenetic evaluation in fetuses with isolated neural tube defects diagnosed by prenatal ultrasound. METHODS: Fifty-five thousand two hundred sixty obstetric ultrasounds performed for various indications at the Indiana University Prenatal Diagnostic Center from July 1988 to March 1994 were reviewed using a computerized data base. Excluding all cases of anencephaly, fetuses with isolated neural tube defects were identified. Maternal demographic data, pregnancy outcomes, level of defect, and fetal karyotype when available were obtained. Statistical analysis was performed using the chi 2 test, when appropriate. P < or = .05 was considered statistically significant. RESULTS: Seventy-seven medical record charts of women with prenatally diagnosed isolated fetal neural tube defects were reviewed. Nineteen pregnancies were terminated, 42 pregnancies were delivered, and 16 pregnancies were lost to follow-up. Karyotypes were available in 43 of the 77 cases (55.8%). The theoretical risk of chromosomal anomalies in this sample population based solely on maternal age was 0.3%. Of the 43 documented karyotypes, seven chromosomal anomalies were discovered (16.3%). The difference was statistically significant (P = .012). Detected chromosomal anomalies included two trisomy 18, two triploid 69,XXX, one triploid 69,XXY, one balanced Robertsonian translocation t(13q,14q), and one inversion in the q arm of the X chromosome. CONCLUSION: The prevalence of karyotypic abnormalities is significantly increased in fetuses with isolated neural tube defects; therefore, prompt antenatal genetic evaluation should be considered in such cases.

Adult↗

PubMed2001

[Frequency of neural tube defects in public maternity during 1999 in Santiago, Chile].

BACKGROUND: Fortification of wheat flour with folic acid in Chile, started in January 2000. This fortification should decrease the incidence of neural tube defects. AIM: To study the incidence of neural tube defects among Chilean newborns, during 1999. MATERIAL AND METHODS: The records of all newborns and stillbirths with a birth weight over 500 g from 9 public maternity hospitals in Santiago in 1999, were reviewed. All neural tube defects, associated or not to other malformations were taken into account. RESULTS: During the study period, 59.627 newborns and 455 stillbirths were analyzed. The global incidence of neural tube defects was 1.56 per 1.000 born (57% women, 42% men and 1% ambiguous sex). Spina bifida was the most frequent neural tube defect found. CONCLUSION: These baseline data will be useful to assess the impact of folic acid fortification of wheat flour.

Chile↗

PubMed2006

Primary prevention of neural tube defects with folate in Western Australia: the value of the Western Australian Birth Defects Registry.

This paper reviews the role of the Western Australian Birth Defects Registry in the primary prevention of neural tube defects. The Registry provides complete and up-to-date information on all neural tube defects (NTD), including terminations of pregnancy. These data have been used to determine a baseline rate of NTD and to monitor trends in NTD over time, when health promotion of folic acid supplement use and voluntary fortification of food with folate were introduced. The register has also been used to investigate NTD in special populations (Indigenous infants in Australia) and as a sampling frame for case control studies. The data derived from these studies have been used to assist in assessing whether mandatory food fortification in Australia is indicated to prevent NTD.

Australia↗

PubMed1997

Antecedent circumstances surrounding neural tube defect births in 1990-1991. The Steering Committee of the National Confidential Enquiry into Counselling for Genetic Disorders.

OBJECTIVE: To investigate births with neural tube defects at a time when most districts were screening for the condition. The objective was to document the circumstances surrounding each affected birth and assess the care provided against given standards. DESIGN: Retrospective review of antenatal casenotes by the obstetric team. POPULATION: Three hundred and eight births in England and Wales in 1990 to 1991 were reported to the Office of Population Census Survey (OPCS) to involve neural tube defects. Sufficient information was available to identify both the woman and the obstetrician in 213 pregnancies. Details were obtained from a questionnaire completed by the obstetric team for 168 (79%). In 20/168 cases either the reported outcome was not a live birth/stillbirth or the pregnancy did not involve a neural tube defect: eight resulted in a 'normal' infant, eight were terminated and in four the abnormality was not a neural tube defect. Thus 148 eligible cases were available for analysis. RESULTS: Of the 148 births, the anomaly was not detected prenatally or detected later than 25 weeks of gestation in 98 cases (66%), diagnosed in a multiple pregnancy in 24 (16%) and diagnosed prenatally but the woman chose to continue the pregnancy in 26 (18%). Of the 98 births not detected prenatally or detected late during pregnancy, the surrounding circumstances were that screening was declined in six cases (4%), screening was not offered due to late booking in 30 (20%), serum alpha-fetoprotein screening gave a false negative result in eight (5%), ultrasound screening gave a false negative result in 29 (20%), both screening methods gave false negative results in 17 (11%) and other reasons in eight (5%). The estimated sensitivity of ultrasound screening for anencephaly was 100%. For spina bifida the estimated sensitivity for singleton pregnancies is higher for serum alpha-fetoprotein screening, 84% to 92%, than ultrasound screening, 70% to 84%, for a range of assumptions regarding the degree of under-reporting to OPCS of live births and terminations. CONCLUSIONS: Late booking precluded the offer of screening tests in a substantial proportion (22%) of cases. The presence of multiple fetuses including one or more with a neural tube defect was a serious additional complication in prenatal screening, diagnosis and counselling. Screening for neural tube defects was widespread in 1990 to 1991, although variations in the services provided were documented. Ultrasound scanning was a major component but was associated with a lower sensitivity than maternal serum alpha-fetoprotein screening for neural tube defects other than anencephaly.

Anencephaly↗

PubMed1988

Birth prevalence and recurrence rates of neural tube defects in southern Alberta in 1970-81.

Given the observed variation in birth prevalence and recurrence rates of neural tube defects, it is important to obtain such data specific to a given locality for research and genetic counseling purposes. A review of hospital medical charts, the patient lists of the Medical Genetics and Myelomeningocele clinics at Alberta Children's Hospital and data from the Canadian Congenital Anomalies Surveillance System revealed the annual birth prevalence rate of neural tube defects in southern Alberta in 1970-81 to be 1.62/1000 total births. This figure suggests southern Alberta to be a low-frequency area. There was no significant variation in the annual rates of spina bifida, encephalocele or all neural tube defects combined over the study period. A significant linear decline in the frequency of births of anencephalic infants, however, was noted (p = 0.025). Information on the total reproductive history of the mothers revealed that the empiric risk of recurrence of a neural tube defect was 2.2%, and the risk to all siblings was estimated to be 2.3%. In future prevalence studies multiple sources of case ascertainment should be used, including data on pregnancies terminated because of a fetal neural tube defect.

Alberta↗