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PubMed1996

Fortification of the food supply with folic acid to prevent neural tube defects is not yet warranted.

The relationship between adequate folate intake by pregnant women and reduced risk of delivering infants with neural tube defects (NTDs) has raised the public health issue of increasing folate intake among women of reproductive age. The U.S. Food and Drug Administration has proposed fortifying cereal and grain products with folate, although at a level less than half that recommended by its sister agency, the Centers for Disease Control and Prevention. We question the wisdom of fortifying foods with folate at this time, given a variety of uncertainties, which include the following: 1) the fact that neural tube defects seem to be a multifactorial group of disorders that are polygenic as well, so folate will not help in all or perhaps even in most cases; 2) the incidence of NTDs, which varies geographically, has been decreasing in the United States for years; 3) fortifying more food with folate may pose safety concerns for some not as risk for NTDs; 4) no dose-response relationship has been established between folate and NTDs; and 5) fortification in this case would represent a conceptually new intervention strategy for addressing what may be a metabolic abnormality where pharmacological doses of a nutrient may be required. Launching a major nutritional intervention before better understanding the relationship between nutrients and NTDs and without reasonable assurance that it will not shift health risks from one group (developing embryos) to another (primarily adults with pernicious anemia) might prove ineffective and/or harmful.

Adult↗

PubMed1996

Hispanic origin and neural tube defects in Houston/Harris County, Texas. II. Risk factors.

Several investigators have reported Hispanics to be at elevated risk for neural tube defects (anencephaly and spina bifida). Factors contributing to this risk have not been established. The authors conducted a case-control study of neural tube defects (NTDs) among births occurring in Harris County, Texas, from April 1, 1989, through December 31, 1991. Through the use of multiple ascertainment methods, 59 cases of anencephaly and 32 cases of spina bifida were detected. Controls (n = 451) were sampled for the same time period from Harris County vital records. Regardless of how Hispanic ethnicity was classified, having a Hispanic parent was a risk factor for both anencepahly and spina bifida. The primary etiologic question was whether increased NTD risk in Hispanics is explained by maternal diabetes or by other factors (e.g., maternal birthplace, prenatal care, reproductive history, age, socioeconomic status). Mexico-born Hispanics were no more likely than Texas-born Hispanics to deliver a fetus or infant with an NTD. Having a Hispanic mother was a risk factor for anencephaly among infants born to women with early prenatal care (odds ratio (OR) = 4.54, 95% confidence interval (CI) 2.21-9.40) but not for those born to latecomers. Earlier prenatal care seemed "protective" for non-Hispanics (OR = 0.18, 95% CI 0.06-0.65) but not for Hispanics. After simultaneous adjustment for eight variables in multivariate analysis, having a Hispanic (versus non-Hispanic) mother remained a strong risk factor for both anencephaly (OR = 2.58, 95% CI 1.19-5.61) and spina bifida (OR = 3.71, 95% CI 1.48-9.31). Any previous pregnancy termination/fetal loss was also associated with anencephaly in a final logistic regression model (OR = 2.48, 95% CI 1.20-5.10), and having a teenage mother (aged < 20 years) approached significance (OR = 2.21, 95% CI 0.92-5.31). "Hispanic mother" was the only study variable significantly associated with spina bifida in multivariate analysis. Results for diabetes suggested no association with anencephaly (OR = 1.24, 95% CI 0.25-6.17). An increased risk of NTDs among Hispanics remained after controlling for other factors. For anencephaly, this risk might be partially explained by economic and cultural differences between Hispanics and non-Hispanics, and the effect of these factors on rates of prenatal diagnosis and elective pregnancy termination.

Adult↗

PubMed1988

Clinical, genetic, and epidemiological factors in neural tube defects.

We examined clinical, genetic, and epidemiologic factors among 512 probands with nonsyndromal neural tube defects (NTDs). Data were analyzed after grouping the probands in four different ways with respect to pathological features and putative pathogenic mechanisms. Apparently unrelated congenital anomalies occurred more frequently among probands with craniorachischisis (62%), encephalocele (30%), or multiple NTDs (25%) than among probands with anencephaly (14.7%) or spina bifida (10.1%) (P much less than .0001). Unrelated congenital anomalies occurred less often among probands with low spina bifida (6.7%) than among probands with high spina bifida (19.5%). NTDs were seen in 7.8% of the siblings of probands with high spina bifida but in only 0.7% of the siblings of probands with low spina bifida, in 2.2% of the siblings of anencephalic probands, and in none of the siblings of probands with craniorachischisis, encephalocele, or multiple NTDS (P less than .001). In all 16 families in which two siblings had NTDs, both had either defects of the type associated with abnormal primary neurulation or defects of the type associated with abnormal canalization. High spina bifida and multiple NTDs were found more frequently than expected among the Sikh probands (P less than .02). The frequency of non-NTD congenital anomalies was higher among siblings of Sikh probands (8.8%) than among siblings of other probands (2.4%) (P less than .05). This excess was due to the occurrence of hydrocephalus without spina bifida in four of 68 siblings of Sikh probands.

Adult↗

PubMed1993

First-trimester biochemical screening for fetal chromosome abnormalities and neural tube defects.

Alpha-fetoprotein (AFP), unconjugated oestriol (UE3), intact human chorionic gonadotrophin (intHCG), and the free beta subunit of chorionic gonadotrophin (F beta HCG) were investigated in a series of 21 chromosomally abnormal and 14 open neural tube defect pregnancies ascertained from a series of 14,000 prospectively collected maternal serum samples at 6-14 weeks' gestation. In 16 cases of Down's syndrome, significant reductions were found for AFP (0.65 multiples of the normal median) and UE3 (0.67 MOM). IntHCG levels were unaltered (0.97 MOM) but a significant increase was found for F beta HCG (1.96 MOM). Significant correlations were found for AFP and UE3 in the controls and for intHCG and F beta HCG in both the control and the Down's syndrome pregnancies. In a group of five trisomy 18 pregnancies, median MOMs were for AFP 0.71, for UE3 0.34, for intHCG 0.27, and for F beta HCG 0.15. None of 13 pregnancies with open neural tube defects at 8-13 weeks gestation had elevated maternal serum AFP levels, whereas matched second-trimester samples from the same pregnancies at 16-18 weeks gestation all had significantly elevated AFP levels. Thus, biochemical screening for chromosome abnormalities may be practicable in the first trimester using free beta human chorionic gonadotrophin in combination with AFP and maternal age. However, a separate screening protocol using AFP at 15-18 weeks gestation would still be required for effective detection of neural tube defects.

Biomarkers↗

PubMed2006

Adverse reproductive outcomes among pregnancies of aunts and (spouses of) uncles in Irish families with neural tube defects.

Adverse pregnancy outcomes may be more frequent among sibs of individuals with neural tube defects (NTDs), and transmission of risk in families with an NTD may be more frequent among maternal relatives. In a study designed to evaluate matrilineal risk for NTDs, we compared adverse pregnancy outcomes among maternal and paternal first cousin pregnancies. Pregnancy histories were obtained by interview with 288 uncles and aunts (parents of the first cousin pregnancies) in 48 Irish NTD families. We analyzed pregnancy outcomes (preterm deliveries, stillbirths, and miscarriages) among 1,033 singleton first cousin pregnancies and compared risk among maternal versus paternal relatives. Maternal first cousin pregnancies were more likely to end adversely when compared to paternal first cousin pregnancies (17.4% vs. 11.7%, P = 0.01). In a logistic regression analysis of pregnancies unaffected by birth defects, maternal line remained independently associated with adverse outcomes (odds ratio (OR) = 1.55, 95% confidence interval (CI) 1.06, 2.27) after controlling for NTD type, maternal age, maternal smoking during pregnancy, first cousin pregnancy's year of birth. The excess risk with maternal line related mainly to spina bifida occulta families (OR = 42.4; CI 2.64, 681; P = 0.008); risk in open spina bifida families was 1.24 (CI 0.82, 1.87; P = 0.3). These results support the hypothesis of excess risk for adverse pregnancy outcomes among maternal relatives in NTD families. Further work is needed, epidemiological as well as clinical and molecular, not only to confirm these findings, but also to define the underlying biological mechanisms linking adverse reproductive outcomes, excess maternal risk and occurrence of NTDs.

Adult↗

PubMed1996

Prepregnant weight in relation to risk of neural tube defects.

OBJECTIVE: To examine the relation between prepregnant weight and the risk of neural tube defects (NTDs). DESIGN: Data were collected from 1988 to 1994 in a case-control surveillance program of birth defects. SETTING: Study subjects were ascertained at tertiary care centers and birth hospitals in the greater metropolitan areas of Boston, Mass, and Philadelphia, Pa, and in southeastern Ontario. PARTICIPANTS: Cases were 604 fetuses or infants with an NTD identified within 6 months of delivery. Controls were 1658 fetuses or infants with other major malformations identified within 6 months of delivery. For 1992 to 1994, there were 93 control infants without major malformations. MAIN OUTCOME MEASURE: Relative risk of NTDs in infants or fetuses for different maternal weights. RESULTS: Relative to women who weighed 50 to 59 kg, risk of NTDs increased from 1.9 (95% confidence interval [CI], 1.2 to 2.9) for women weighing 80 to 89 kg to 4.0 (95% CI, 1.6 to 9.9) for women weighing 110 kg or more. When women were classified according to daily intake above or below the recommended level of 400 micrograms of folate, approximate threefold increases in risk were estimated for the heaviest weights in both groups. Intakes of 400 micrograms of folate or more reduced risk of NTDs by 40% among women weighing less than 70 kg, but no risk reduction was observed among heavier women. CONCLUSION: The risk of NTDs increased with increasing prepregnant weight, independent of the effects of folate intake.

Adult↗

PubMed2004

Independent mutations in mouse Vangl2 that cause neural tube defects in looptail mice impair interaction with members of the Dishevelled family.

Mammalian Vangl1 and Vangl2 are highly conserved membrane proteins that have evolved from a single ancestral protein Strabismus/Van Gogh found in Drosophila. Mutations in the Vangl2 gene cause a neural tube defect (craniorachischisis) characteristic of the looptail (Lp) mouse. Studies in model organisms indicate that Vangl proteins play a key developmental role in establishing planar cell polarity (PCP) and in regulating convergent extension (CE) movements during embryogenesis. The role of Vangl1 in these processes is virtually unknown, and the molecular function of Vangl1 and Vangl2 in PCP and CE is poorly understood. Using a yeast two-hybrid system, glutathione S-transferase pull-down and co-immunoprecipitation assays, we show that both mouse Vangl1 and Vangl2 physically interact with the three members of the cytoplasmic Dishevelled (Dvl) protein family. This interaction is shown to require both the predicted cytoplasmic C-terminal half of Vangl1/2 and a portion of the Dvl protein containing PDZ and DIX domains. In addition, we show that the two known Vangl2 loss-of-function mutations identified in two independent Lp alleles associated with neural tube defects impair binding to Dvl1, Dvl2, and Dvl3. These findings suggest a molecular mechanism for the neural tube defect seen in Lp mice. Our observations indicate that Vangl1 biochemical properties parallel those of Vangl2 and that Vangl1 might, therefore, participate in PCP and CE either in concert with Vangl2 or independently of Vangl2 in discrete cell types.

Adaptor Proteins, Signal Transducing↗

PubMed2002

[Dynamic monitoring of neural tube defects in China during 1996 to 2000].

OBJECTIVE: The database from Chinese Birth Defects Monitoring Network was used to describe the epidemiological features and secular trends of neural tube defects (NTDs) prevalence during Jan. 1996 to Dec. 2000, including anencephaly, spina bifida and encephalocele. METHODS: Data were collected with hospital-based cluster sampling method. During the period, all live or still births with 28 weeks or more of gestation were assessed within seven days after delivery. RESULTS: There were 2 873 case with NTDs identified from 2 281 616 births, with an overall prevalence rate of 12.95 per 10,000 births. And, the prevalence rates of anencephaly, spina bifida and encephalocele were 5.02 per 10,000, 6.30 per 10,000 and 1.64 per 10,000, respectively. Significant falls in overall prevalence rates of NTDs and of anencephaly were observed. The prevalence rates of NTDs were 9.75 per 10,000 and 15.96 per 10,000 in male and female births, respectively, 7.76 per 10,000 and 25.20 per 10,000 in the urban and rural areas, respectively, and 19.90 per 10,000 and 5.81 per 10,000 in north and south China, respectively. The prevalence was higher in the groups with maternal age of less than 20 years and more than 30 years than in those other maternal ages. Preterm babies and babies with low birth weight accounted for 50.9% and 50.6% of perinatal babies with NTDs, respectively, with a perinatal mortality of 77.8%. CONCLUSIONS: In China, the occurrence of NTDs was higher in female births than in male births, higher in the rural than in the urban, and higher in the north than in the south. Annual prevalence rate of NTDs in China presented a declining trend, but still higher than that in the other countries at the same time period. Babies with NTDs were in poor birth quality, higher perinatal mortality and poor prognosis. Effective preventive measures and prenatal diagnosis should be strengthened to reduce the occurrences of neural tube defects.

Adult↗

PubMed1998

Neural tube defects, vitamins and homocysteine.

Folic acid (multivitamins) reduce the recurrence and occurrence of neural tube defects (NTDs). Vitamin profiles seem not suitable to identify women at risk for NTDs. A subset of these women have hyperhomocysteinaemia and a mutation of the gene for thermolabile methylenetetrahydrofolate reductase (MTHFR). From studies with the rat embryo in vitro, it can be concluded that the de- and remethylation cycle of methionine, being folate and vitamin B12 dependent, is crucial for embryonic and fetal growth probably via generation of DNA, proteins and polyamines. Nutrition for the embryo is also supplied by the follicular fluid, the yolk sac, the extraembryonic coelomic cavity and the amniotic fluid.

Animals↗

PubMed2001

Neural tube defects: a different pattern in northern Thai population.

The objective of this descriptive study was to describe the demographic and sonographic patterns of fetal neural tube defects (NTDs) in Thai pregnant women. The study was conducted at Maharaj Nakorn Chiang Mai Hospital, Chiang Mai University. The subjects included all pregnancies with diagnosis of fetal neural tube defects. Basic clinical data of the subjects was prospectively collected at the time of diagnosis for NTDs and followed-up until delivery. Antenatal diagnosis was based on sonographic criteria. The results showed that the incidence of NTDs was 0.66/1,000 births, however, spina bifida was very rare, found in only 0.06/1,000 births, similar to encephalocele. All anencephalic fetuses had no concurrent spina bifida, and only a few cases had other associated anomalies. Ultrasound was able to diagnose NTDs with very high accuracy. All cases of antenatal diagnosis were electively terminated. In conclusion, NTDs in the Thai population were rather rare when compared to that of the Europeans and spina bifida was extremely rare. The accuracy of antenatal diagnosis of NTDs with ultrasound was highly reliable.

Adolescent↗

PubMed1994

Ovulation induction and risk of neural tube defects.

The relation between use of ovulation-inducing drugs and risk of neural tube defects (NTDs) was studied in a case-control surveillance programme. The frequency of any use of such drugs during the 6 months before the last menstrual period or during pregnancy was 3.0% for 1034 mothers of infants and fetuses with NTDs (cases) and 2.8% for 4081 mothers of those with other major congenital malformations (controls) (relative risk 1.1, 95% CI 0.8-1.7). Relative risks for clomiphene and for hormones were 0.8 (0.5-1.3) and 1.5 (0.7-3.4), respectively. These data suggest that use of ovulation-inducing drugs before conception does not increase the risk of NTDs.

Case-Control Studies↗

PubMed1989

A study of the value of measuring maternal serum alpha-fetoprotein for the antenatal diagnosis of neural tube defects.

Two neighbouring centres, both located in an area where the prevalence of neural tube defects (NTDs) is low, were compared to determine if there was any advantage in their differing policies as regards the antenatal detection of NTDs. At both centres routine ultrasound examinations were performed at 16-18 weeks gestation but at Hospital A serum alpha-fetoprotein (AFP) was measured at 16 weeks gestation. The prevalence of NTDs was 1.3 per 1,000 births at Hospital A and 1.7 per 1,000 births at Hospital B. The detection of anencephaly at both hospitals was 100%, however, only 43% of spina bifidas were detected at Hospital A compared with 60% at Hospital B. These results, the loss of two fetuses following amniocentesis at Hospital A and the lower detection rate for NTDs at the hospital employing AFP measurement are discussed.

Anencephaly↗

PubMed1998

Cell kinetics of surgically induced spinal open neural tube defect in chick embryos.

In an attempt to understand cell kinetics of open neural tube defects (ONTDs) in the embryonic stages, chronological changes of cell proliferation and cell death patterns in the surgically induced spinal ONTDs of chick embryos were investigated using proliferating cell nuclear antigen (PCNA) staining and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) method. ONTDs were induced at Hamburger and Hamilton stages 17-19. Compared with the control group, the surgery group showed a lower PCNA labeling index for 5 days after surgery and demonstrated more TUNEL-positive cells at 6 h, 3 and 5 days after surgery. Decreased cell proliferation and enhanced apoptosis were seen in the ventral as well as in the dorsal spinal cord. These results partly explain the functional deficits of ONTDs.

Animals↗

PubMed1987

Retinoic acid-induced selective mortality of splotch-delayed mouse neural tube defect mutants.

The allelic loci splotch (Sp) and splotch-delayed (Spd) cause neural tube defects (NTDs) in mice homozygous for either of these genes. The polymorphic enzyme isocitrate dehydrogenase (Idh-1) in conjunction with a recombination suppressor was used as a genetic marker to identify embryos homozygous for these alleles. A split dose of all-trans retinoic acid (RA) totalling 5.0 mg/kg administered on gestation day 9/15 and 9/18 (days/h) significantly reduced the frequencies of NTD and of mutant genotypes in marked Spd embryos examined on day 16 without significantly increasing the resorption frequency. There was a nonsignificant decrease in the frequencies of NTD and mutant genotypes in embryos examined on day 11 of gestation. Thus, retinoic acid treatment was associated with selective mortality of the homozygous Spd mutants. No evidence of selective mortality was observed in RA-treated Sp embryos.

Alleles↗

PubMedDate not supplied

Folic acid knowledge and use among relatives in Irish families with neural tube defects: an intervention study.

BACKGROUND: Relatives in families where a child has a neural tube defect (NTD) may be at higher risk of having an affected child. Little is known of their level of knowledge and use of folic acid. AIM: To carry out an intervention study intended to increase knowledge and use of folic acid among relatives. METHODS: One hundred aunts and female first cousins (relatives of the proband) were interviewed by telephone before and after receiving an information pack. RESULTS: At baseline, although knowledge of the benefits of folic acid was high (73%), use of folic acid was low (8.8%). After the intervention, knowledge increased and use went up to 19% (p < 0.05). CONCLUSIONS: This study suggests that relatives in Irish NTD families have a high level of information about folic acid benefits. This awareness may not translate into action since the intervention produced only a modest increase in folic acid use overall. Future studies focussing on women who are planning a pregnancy may show larger benefits from intervention.

Adolescent↗

PubMed2006

Antiepileptic drugs: a case report in a pregnancy with a neural tube defect.

While receiving lamotrigine, a patient pregnant with triplets suffered a double fetal neural tube defect. Plasma homocysteine, folate, vitamins B12 and B6 (pyridoxal phosphate), and red cell folate levels were measured in samples while she was receiving folic acid therapy for 1 month during the second trimester of pregnancy. Some mutations were sought, involved in homocysteine metabolism and linked with the folate metabolism. Her results were compared with those of a pregnant woman with normal triplets and with those of 58 pregnant women, with a normal pregnancy. Results indicated a decrease in vitamin B12 and B6 values in plasma in the patient, and a genotype AG (polymorphism A66G) was observed, but was not found in the pregnant woman with normal triplets. Even if lamotrigine therapy is not known to be associated with significant changes in red cells or in serum folate, periconceptional folic acid supplementation is counseled for women, along with periconceptional B12 and B6 vitamin supplementation when their plasma values are decreased.

Adult↗

PubMed1995

Detecting neural tube defects by amniocentesis between 11 and 15 weeks' gestation.

Forty-two open neural tube defects (NTDs) were identified in our series of 7440 amniocenteses tested between 11 and 15 weeks of gestation. Using a cut-off of > or = 2.0 MOM, the detection rate for open NTDs was 95 per cent; 100 per cent each for anencephaly and spina bifida; and 78 per cent for encephalocele. Two encephaloceles had AFP levels less than 2.0 MOM and negative AChEs. Thirty-four (81 per cent) of these NTDs were tested between 13 and 15 weeks and 8 (19 per cent) before 13 weeks. There were 0.6 per cent false positives by AFP (excluding serious abnormalities and fetal death) and 0.1 per cent after AChE. The likelihood of an open NTD after an elevated AFP (> or = 2.0 MOM) was 24 and 77 per cent for any serious abnormality. These results, when combined with an earlier study, indicate that amniotic fluid AFP appears to be as sensitive a test for open NTDs between 13 and 15 weeks as between 16 and 20 weeks. Additional experience is necessary to determine this before 13 weeks.

Acetylcholinesterase↗

PubMed2005

Neural tube defects: is a decreasing prevalence associated with a decrease in severity?

OBJECTIVE: Severe neural tube defects (NTDs) tend to occur with disproportionate frequency in areas of high prevalence. The objective of our study was to determine the birth prevalence of NTDs during a 25-year period at a single institution based in an area of high prevalence for NTDs and to investigate if a decreasing prevalence resulted in a change in the type of NTDs. STUDY DESIGN: All cases of NTD affected births born at the Coombe Women's Hospital during the interval 1975-1999 were reviewed. There were 171,260 births at the Coombe Women's Hospital between 1975 and 1999. During this interval, there were 522 NTD affected births. RESULTS: From 1975 until 1999 the prevalence of NTDs significantly decreased (P < 0.0001). This transition from high to low prevalence was associated with a significant decrease in severe forms of NTDs (P < 0.0001). This decreasing trend in rate and severity of NTD affected births was most dramatic prior to either food fortification or periconceptual folic acid supplementation. CONCLUSIONS: Our transition from high to low prevalence for NTDs has been associated with a significant decrease in severe forms of NTDs.

Anencephaly↗