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PubMed1989

[Epidemiology of neural tube defects in China].

During a period of 12 months (Oct. 1986 to Sep. 1987), 1,243,284 live and still births from 28 weeks of gestation to a period within 7 days after delivery were monitored in 945 hospitals of 29 provinces, cities and autonomous regions of China. A total of 3,404 cases of neural tube defects were recorded, among which there were 1,891 cases of anencephaly (55.6%), 1,050 cases of spina bifida (30.9%) and 463 cases of encephalocele (13.6%). The incidence of neural tube defects in China varied from 6.6 to 105.5 with a mean of 27.4 per 10,000. A female preponderance (35.7 per 10,000) over the male (19.2 per 10,000) was noted (P less than 0.01). The incidence of neural tube defects in the rural area (51.7 per 10,000) is higher than that in the urban area (15.5 per 10,000), (P less than 0.01).

Anencephaly↗
PubMed1993

[Amniotic and serum alphafetoprotein in the chick embryo with neural tube defect].

Although alpha-feto-protein (AFP) is a widely used marker for human neural tube defects (NTD) little is known about the mechanisms for its increase in the amniotic fluid in this condition. For investigating this issue we developed a chick embryo AFP assay and tested it in a NTD experimental model. AFP obtained by electroelution on PAGE/SDS gels from the plasma of 12-day-old embryos was used to produce rabbit polyclonal and mouse monoclonal antibodies. A specific sandwich-type enzyme-immune-assay was developed using both reagents. Sterile aspiration of 5 ml. of albumen from 602 fertile hen eggs on the 27th hour of incubation (Hamburger stages 8 to 11) led to the appearance of NTD in 36 out of the 270 survivors (13%). Amniotic and seric AFP levels were measured on the 15th day of incubation in NTD chicks (n = 11) and in control ones (n = 9) and the results were compared by non-parametric tests. Serum AFP was five times higher in NTD chicks than in controls (119.2 +/- 32.6 vs 523.3 +/- 173.62 micrograms/ml., p < 0.001) and amniotic AFP was absent in control and very increased in NTD animals (0.15 +/- 0.02 vs 87.14 +/- 84 micrograms/ml., p < 0.001). It is concluded that: 1) serum AFP is intriguingly increased in the chick with NTD; 2) since urine is not diversed into the amniotic sac in the avian embryo, the only source of AFP in its fluid is exudation through an open defect. This conclusion is further supported by the absence of amniotic AFP in a chick with a large closed NTD.

Amniotic Fluid↗
PubMed1993

Maternal plasma folate and vitamin B12 are independent risk factors for neural tube defects.

Blood was taken at the first antenatal clinic from 56,049 pregnant women. Neural tube defect (NTD) pregnancies (81) were compared to controls (247) for plasma vitamin B12 (B12) (ng/l), plasma folate (microgram/l), and red cell folate (RCF) (microgram/l). Median values were significantly different and were, respectively, 243 and 296 (p = 0.001); 3.47 and 4.59 (p = 0.002); and 269 and 338 (p < 0.001). There was a significant correlation between plasma B12 and RCF in cases (r = 0.31, p = 0.004) but not in controls (r = 0.02, p = 0.725). In cases only, multiple regression showed that both plasma B12 and plasma folate influenced the maternal RCF (multiple r = 0.68, p < 0.001). Plasma folate and plasma B12 were independent risk factors for NTDs, suggesting that the enzyme methionine synthase is involved directly or indirectly in the aetiology. The levels of folate and B12 where increased risk occurred were not those usually associated with deficiency, calling for a re-evaluation of their recommended daily allowances. Whether the aetiology is purely nutritional or a metabolic defect, this study suggests that consideration should be given to including B12 as well as folic acid in any programme of supplementation or food fortification to prevent NTDs.

Adult↗
PubMed1997

Down syndrome and neural tube defect screening: the value of using gestational age by ultrasonography.

OBJECTIVE: Our goal was to determine whether gestational age should be based on ultrasonographic evaluation or last menstrual period data in the interpretation of second-trimester maternal serum screening for Down syndrome and open neural tube defects. STUDY DESIGN: Initial and revised screen-positive rates and detection rates were reviewed for women undergoing triple-marker testing (maternal serum alpha-fetoprotein, human chorionic gonadotropin, and unconjugated estriol). The study population consisted of > 24,000 women at 15.0 to 21.9 weeks' gestation with approximately 60% of test interpretations based on ultrasonographic evaluation of gestational age. Gestational age and screening results were compared for 24 Down syndrome pregnancies in which both ultrasonography and last menstrual period dating were available. RESULTS: Both initial and revised screen-positive rates for Down syndrome were significantly lower when ultrasonographic data were used compared with last menstrual period dating. The detection rate for Down syndrome appeared to be higher with ultrasonographic dating (approximately 76% vs 60% for last menstrual period dating). Down syndrome fetuses had a significantly shorter gestational age when evaluated by ultrasonography (relative to last menstrual period dating), but a similar trend was also seen in control pregnancies. Initial and revised screen-positive rates for open neural tube defects were higher for women who had received an ultrasonographic examination compared with the rates for those women referred with only last menstrual period data. The detection rates for open neural tube defects were similar for both methods of pregnancy dating. CONCLUSION: By use of ultrasonographic measurement of gestational age, the number of amniocenteses performed to detect Down syndrome can be substantially reduced while detection rates are maintained or improved.

Adult↗
PubMed1980

Diagnostic ultrasound: early detection of fetal neural tube defects.

In a series of 366 patients identified as at risk for a fetal neural tube defect (NTD) before the 24th week of pregnancy, 64 had an abnormal fetus. The abnormalities included anencephaly (39), open spinal defect (17), closed spinal defect (2), encephalocele (1), and a miscellany of other abnormalities (5). An ultrasound examinaton prior to diagnostic anmiocentesis positively identified all anencephalic fetuses, the fetus with the encephalocele, and 15 of the 19 fetuses with spina bifida. The spinal defects in 3 of the remaining 4 fetuses were demonstrated at a second examination. Since both amniotic fluid alpha-fetoprotein (AFP) assays and ultrasound examination have been shown to give false results in the diagnosis of NTDs, the importance of using 2 independent diagnostic techniques is stressed. In patients with elevated levels of maternal serum AFP, a careful ultrasound examination, in addition to identifying the majority of cases associated with an abnormal fetus, provided a good explanation for the elevation in over half of the remainder. In this series more than half the patients (40/69) who underwent amniocentesis because of raised maternal serum AFP levels were shown to have an abnormal fetus.

Amniotic Fluid↗
PubMed2006

Surveillance of neural tube defects in Israel: the effect of the recommendation for periconceptional folic acid.

BACKGROUND: Open neural tube defects are among the most common severely disabling birth defects. Secondary prevention by early diagnosis during pregnancy and abortion of affected fetuses lead to a marked reduction of NTD incidence at birth. For primary prevention of these defects, in August 2000 the Israel Ministry of Health issued guidelines recommending a daily 0.4 mg folic acid supplement for all women in their childbearing years with special emphasis on the 3 months preceding conception and the first trimester of pregnancy. OBJECTIVES: To compare the epidemiologic characteristics of NTD in Israel before and after the guidelines for folic acid supplementation. METHODS: A national registry of NTD was begun in 1999. Since the Ministry of Health published the recommendation for folic acid supplementation in mid-2000, the years 1999-2000 represent the status prior to the recommendation and the years 2002-2004 the status after. RESULTS: A marked decline in the rate of spina bifida was observed in the last 3 years (from 4.9 to 2.7 per 10,000 live births among Jews and 9.5 to 6.2 among Arabs and Druze). There was no apparent reduction for anencephaly. CONCLUSIONS: Following the Ministry of Health guidelines on folic acid supplementation for women in the reproductive age, a marked reduction in the rates of NTD was observed. In light of this apparent success, continuous efforts should be made to increase the percentage of women taking the supplementation and, especially, to introduce folic acid fortification.

Dietary Supplements↗
PubMed2004

Enhancement of re-closure capacity by the intra-amniotic injection of human embryonic stem cells in surgically induced spinal open neural tube defects in chick embryos.

To evaluate the re-closure promoting capacity of human embryonic stem (hES) cells injected into the amniotic cavity on spinal open neural tube defects (ONTDs) of chick embryos, neural tubes were opened at Hamburger and Hamilton stage 18 or 19 and the embryos were divided into three groups: a control group (no injection), a vehicle group, and a hES cell group (injection of 20,000 hES cells immediately after neural tube incision). On postoperative days 3, 5, and 7, ONTDs were significantly more re-closed in the hES cell group than in the other two groups. hES cells were present at the area in the process of re-closure, and covered ONTDs, but were not found in the re-closed area, suggesting indirect effects rather than cell replacement on the neural tissue.

Amnion↗
PubMed1985

Maternal serum alpha-fetoprotein in twin pregnancies uncomplicated by neural tube defect.

The maternal serum alpha-fetoprotein concentration was measured between 16 and 20 weeks in 145 twin pregnancies in which neither fetus had a neural tube defect. When the maternal serum alpha-fetoprotein concentration was less than two multiples of the singleton median, pregnancy outcome was good; the extended perinatal mortality rate was 32.6/1000, mean birth weights for the first and second twins were 2507 and 2443 gm, respectively, and mean gestation at delivery was 36 weeks, 6 days. When the maternal serum alpha-fetoprotein concentration was greater than four multiples of the singleton median, the outcome was poor; the extended perinatal mortality was 400/1000, mean birth weights were 1963 and 1523 gm, and mean gestation at delivery was 32 weeks, 4 days. The negative correlations of maternal serum alpha-fetoprotein concentration with birth weight and gestation at delivery were highly significant. Maternal serum alpha-fetoprotein concentration in midpregnancy is a useful predictor of outcome in twin pregnancy, independent of the occurrence of neural tube defect, and it appears to be related to the timing of delivery rather than fetal growth.

Birth Weight↗
PubMed1998

Preventing neural tube defects: the importance of periconceptional folic acid supplements.

OBJECTIVE: To inform the obstetrician-gynecologist of recent scientific evidence regarding the use of supplemental folic acid for prevention of neural tube defects (NTDs). DATA SOURCES: We selected English language articles via MEDLINE published from January 1990 through February 1997, using the search terms "folic acid" and "neural tube defect." Additional sources were identified through cross-referencing and through searching selected journals published from March through October 1997. METHODS OF STUDY SELECTION: Articles were selected on the basis of their relevance to the relationship between folate intake and NTD incidence, mechanisms of folate responsive NTD formation, and folate provision strategy. We referenced 55 papers in total. TABULATION, INTEGRATION, AND RESULTS: The majority of evidence demonstrates a decreased incidence of NTDs with increased folic acid consumption. The most convincing trials were performed in Europe among women who were planning pregnancy by using multivitamin or folic acid supplements. Some studies suggest that the protective effect of folate is explained, in many cases, not through correction of dietary deficiencies, but through correction of metabolic defects. Other evidence implies that it reduces NTDs by causing abortion of affected conceptuses. Supplemental folic acid tablets are the most proven means of improving an individual's folate status, but ensuring compliance with a strategy using vitamin tablets is problematic. CONCLUSION: Women of reproductive age should be advised to take multivitamin supplements containing 0.4 mg folic acid daily. Women with previously affected offspring who intend to become pregnant should take daily supplementation containing 4 mg of folic acid in the periconceptional period to reduce the risk of recurrence.

Female↗
PubMed1985

Epidemiology of neural tube defects in South America.

We present data from the Latin American Collaborative Study of Congenital Malformations (ECLAMC) on prevalence rates and etiologic factor associations in neural tube defects. Two series of data are analyzed: the A series, including 740,139 consecutive infants born in the 1967-1979 period suitable for secular trend analysis and case-control study of risk factors; and the B series, including 255,834 consecutive stillborn and liveborn infants of the 1980-1982 period suitable for prevalence rate analysis. Anencephaly was registered in 6.0/10,000 births, A spina bifida aperta in 6.2/10,000 births, and cephalocele in 2.4/10,000 births. A stable secular trend was observed for the frequency of all three neural tube defect types. Spina bifida was more frequent in Chile than in the rest of South America. No differences in prevalence rates were seen between tropical and non tropical areas. Parental consanguinity and environmental prenatal factors including maternal illnesses, drug intake, and radiation exposure were found in association with anencephaly and spina bifida.

Anencephaly↗
PubMed1985

Sibs of probands with neural tube defects--a study in the Federal Republic of Germany.

Data for the risk of neural tube defects in sibs of affected children are needed for genetic counselling, for decision on prenatal studies, and for planning of preventive measures. Data have been reported from various populations but were lacking for Germany. This study presents data on the siblings of 240 index patients in the Western part of the Federal Republic of Germany. The prevalence among sibs of affected individuals was found to be 2.6%. This figure agrees well with reports from other countries in Continental Europe and the United States, and fits the expectation of lower recurrence risks in low incidence populations.

Abortion, Spontaneous↗
PubMed1994

Multifactorial inheritance of neural tube defects: localization of the major gene and recognition of modifiers in ct mutant mice.

Neural tube defects (NTD) in humans have been considered to have a multifactorial aetiology, however the participating genes have not been identified. The curly-tail (ct) mutant mouse develops NTD that resemble the human malformations in location, pathology and associated abnormalities. Moreover, there appears to be multifactorial influence on the incidence of NTD in offspring of curly-tail mice. We now describe a linkage analysis that localizes the ct gene to distal chromosome 4 in mice. Further analysis using recombinant inbred strains demonstrates the presence of at least three modifier loci that influence the incidence of NTD. This study provides definitive evidence for multifactorial inheritance in a mouse model of human NTD.

Abnormalities, Multiple↗
PubMed1995

Periconceptional folic acid and neural tube defects: public health issues.

This review examines evidence linking periconceptional folic acid intake to neural tube defects (NTDs) and related public health issues in the United States and developing countries. Sources of information were identified through on-line searches (Medline, UCAT-University of Connecticut) and by contacting researchers in the field. The distribution of NTDs varies across regions. Recurrent NTDs can be prevented with high-dosage folic acid supplementation during periconception, but it is not clear if such a protective effect can be achieved with lower dosages or in low-NTD-risk populations. Overall, it appears that women with a previous NTD pregnancy should receive folic acid supplementation during periconception under medical guidance. Dietary counseling regarding foods rich in folate should be given to all women of childbearing age. However, primary prevention of NTDs through widespread food fortification with folic acid seems unwarranted in both the United States and developing countries due to the low prevalence of NTDs relative to other problems and a potentially unfavorable benefit/risk ratio.

Developing Countries↗
PubMed1986

Increased levels of apo-transcobalamins I and II in amniotic fluid from pregnant women with previous neural tube defect offspring.

In an attempt to identify biochemical components of the genetic predisposition to neural tube defects (NTDs), levels of folate, cobalamin, apo-transcobalamins I and II and alpha-fetoprotein were studied in midtrimester amniotic fluid from 24 pregnant women who had previously had a child with NTD. The control group consisted of 76 mothers, subjected to amniocentesis for reasons other than risk of NTD in offspring. Only pregnancies with normal outcome were included. No differences were found between groups for levels of folate, cobalamin or alpha-fetoprotein. Folate intake or metabolism did not appear to differ between groups. In contrast, the level of apo-transcobalamin I was doubled and the level of apo-transcobalamin II tripled in amniotic fluid from women who had had a child with NTD compared with the control group. Since the variation in apo-transcobalamin II in adults is to a high degree genetically determined, the present results may suggest that the genetic predisposition to NTD is associated with variation in this protein. Further studies are needed to substantiate or reject this possibility.

Adult↗
PubMed2000

Reproductive history in mothers of children with neural tube defects.

The reproductive history of 100 women with at least 1 child with a neural tube defect (NTD) has been studied. The data analyzed correspond to the period previous to their first visit to a genetic counseling service. A total of 204 pregnancies resulted in 205 outcomes. Of the 100 sibships, 14 (14%) had more than 1 affected member. The pregnancy was shorter than 28 weeks in 56/205 (27%) of the total outcomes. Of 104 evaluable previous outcomes, 34 corresponded to short pregnancies, positioned before an affected (23/60, 38%), a healthy (2/18, 11%), or an undiagnosed product (9/26, 35%). Short pregnancies subsequent to affected outcomes were also increased. The inter-gestational interval varied according to diagnosis: it was longer in the affected group than in the healthy one (0.1 > p > 0.05) and the subsequent intervals were shorter for the affected group (p < 0.05). An increased number of abortions adjacent to affected offspring and a changing fertility pattern, depending on the product diagnosis, point to an environmental etiological component in this high-risk NTD group of mothers.

Abortion, Spontaneous↗
PubMed2006

Are the recommendations on the prevention of neural tube defects working?

Many studies showed that reduction by an estimated 80% or more of neural tube defects (NTD) by consumption of folic acid from before conception is achievable. The objectives of this study were to evaluate the effectiveness of recommendations on folic acid aimed at reducing the occurrence of NTD in our region. Cases of NTD were ascertained among liveborn infants, stillbirths, and terminations of pregnancy. Incidences and trends in rates of NTD before and after 1992 (the year of the first recommendations) and before and after 1995 (the year of local recommendations) were obtained. The results showed that the issuing of recommendations on folic acid was followed by no detectable improvement in the trends of incidence of NTD. The rates of NTD per 10,000 were before 1992 9.07, from 1993 to 1995 8.14, and after 1995 10.62, respectively. The incidence rate ratios (IRRs) were not different from 1.00. In conclusion new cases preventable by folic acid continue to accumulate. Recommendations alone did not influence trends in NTD in our country up to 11 years after the confirmation of the effectiveness of folic acid in clinical trials. New strategies are needed.

Anencephaly↗
PubMed2000

Neural tube defects and the 13q deletion syndrome: evidence for a critical region in 13q33-34.

Neural tube defects (NTD) are common findings in the 13q deletion syndrome, but the relationship between the 13q- syndrome and NTDs is poorly understood. We present a child with a 13q deletion and lumbosacral myelomeningocele. This was a boy with microcephaly, telecanthus, minor facial anomalies, and ambiguous genitalia. Cytogenetic and fluorescence in situ hybridization analysis showed a de novo 46,XY,del(13)(q33.2-->qter) with no visible translocation. By using microsatellite markers, the deletion breakpoint was mapped to a 350-kb region between D13S274 and D13S1311 and was paternal in origin. An analysis of 13q deletions with NTDs, including the present case, suggests that a deletion in 13q33-34 is sufficient to cause an NTD. The deletions associated with NTDs are distal to and nonoverlapping with the previously defined critical region in 13q32 for the major malformation syndrome [Brown et al., 1999: Am J Hum Genet 57: 859-866]. Our analysis also suggests that one or more genes in 13q33-34 produces NTDs by haploinsufficiency.

Abnormalities, Multiple↗