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The determination of AFP in amniotic fluid for the prediction of neural tube defects fails in cases of myelomeningoceles which changes their status from the open to the closed form. AFP values laying in a borderline range require a fundamental clarification by ultrasound examination for the detection of spinal malformation.
In 20 amniotic-fluid samples taken in the second trimester from pregnancies in which the fetus had a neural-tube defect, the proportion of the total viable cell which adhered to glass surfaces after 20 hours in culture ranged from 9 to 100%. In 92 normal amniotic fluids this proportion was less than 6%. Furthermore, the morphology of the rapidly adhering cells was characteristic in spina bifida (8 cases) and anencephaly (12 cases) and distinct from the epithelioid-like cell seen in normal amniotic fluids, including many which were grossly blood-stained. A sample of amniotic fluid from fetal exomphalos and one from a pregnancy in which the placenta had been repeatedly traversed during amniocentesis had proportions of adherent cells in the pathological range, but the morphologies were very different from those seen in neural-tube defects. It is suggested that the techniques described here will be useful adjuncts to amniotic-fluid alpha-fetoprotein determination in the early diagnosis of fetal abnormality, particularly in blood-stained samples.
Records of almost 174,000 consecutive births at six Brooklyn hospitals during the years 1968-1976 were reviewed for congenital neural tube defects. Prevalence of anencephaly, myelomeningocele and occipital encephalocele combined was significantly higher in infants delivered to mothers born in Puerto Rico than in offspring of non-Puerto Rican whites or blacks. The association of prevalence rates with ethnicity remained significant after adjustment for several variables. However, when adjustment was made for private or service status the difference between Puerto Ricans and whites, although still appreciable, was no longer statistically significant. No significant differences in prevalence rates between whites and blacks were observed. Sex ratios of affected infants were close to unity in each ethnic group. Statistically significant associations were found between the prevalence of neural tube defects and parity, gravidity and economic status. The patterns of these associations varied among the ethnic groups. A declining trend in the prevalence of myelomeningocele was observed for all ethnic groups.
OBJECTIVES: To study the epidemiological characteristics of neural tube defects (NTD) classified according to the theory of multi-site closure of the neural tube and to correlate several factors with the failure of different closure sites. MATERIAL AND METHODS: We used the data from the Spanish Collaborative Study of Congenital Malformations (ECEMC), collected from April 1976 to April 1995. During this time, 757 NTD of non-syndromic origin were diagnosed. These were classified into groups according to the failure of the point of closure and a range of variables were analyzed by comparing the different groups of NTD with each other. RESULTS AND CONCLUSIONS: Among non-syndromic NTD, 2.11 % recurred in siblings. However, the real recurrence rate in our population is 2.63 %, which corresponds with the recurrence rate observed before 1986. From this year the recurrence rate was modified by the legal possibility of abortion after prenatal diagnosis. The infants with NTD classified according to multi-site closure failure of neural tube differed in weight, mortality, maternal use of valproic acid, and maternal diabetes mellitus. While valproic acid is more specific to failure of closure sites 1 and 1 5, maternal diabetes mellitus preferentially affects failure of closure site 4. Closure site 4 is clearly genetically determined: it is frequently observed in genetic syndromes, predominantly affects females and is associated with a higher rate of maternal abortions and higher recurrence. Moreover, it is frequently observed in infants with multiple congenital anomalies and is associated with a higher rate of malformations among relatives.
Clarke et al. suggested that women who have had a spontaneous abortion are at an increased risk in their next pregnancy of producing an offspring with a neural tube defect (NTD). A matched case-control study was carried out to test the related hypothesis that a spontaneous abortion occurring in the 6-month period prior to the conception of a pregnancy (recent spontaneous abortion) is a risk factor for the development of an NTD in that pregnancy. The cases were 177 singleton pregnancies to non-primigravida Leicestershire women, which were affected by non-syndromal NTDs between 1976 and 1989. Two control pregnancies were matched with each case on intended place of delivery and date of maternal last normal menstrual period (LNMP). After adjusting for potential confounders, recent spontaneous abortion was found to be associated with a decreased relative risk of neural tube defect, odds ratio 0.46, 95% confidence interval 0.20, 1.07. The result provided little evidence in favour of the hypothesis, suggesting instead that prior spontaneous abortion has a protective effect in relation to subsequent NTD development rather than being a major risk factor in the aetiology of NTDs.
Twins concordant for elevated alpha-fetoprotein (AFP) and acetylcholinesterase (AChE) and discordant for neural tube defect (NTD) and sex are reported. A literature review reveals instances of termination of twin pregnancies with one normal and one abnormal fetus, partly based on concordant high AFP and positive AChE (although discordant on ultrasound examination). The levels of AFP and AChE in twin pregnancies are probably a function of the number of layers of fetal membranes separating twin sacs; dichorionic, diamniotic membranes allow transfer of AFP; monochorionic, diamniotic membranes allow transfer of both AFP and AChE. Cautious interpretation of biochemical findings and reliance on high resolution ultrasonography are suggested.
Between September 1st 1990 and Juli 31st 1993, 5071 pregnant women were screened prospectively by the "triple-test", including maternal serum alpha-fetoprotein, human chorionic gonadotropin and unconjugated oestriol in order to detect chromosomal anomalies and open neural tube defects. The serum samples were collected in collaboration with the obstetricians of the region of West-Mecklenburg and North-West-Brandenburg. Laboratory testing using radioimmunoassays was performed between weeks 15 and 20 of gestation, all serum specimens being investigated in only one institution. The original alpha-software from Wald et al. was the basis for calculating the statistical risk for Down's syndrome. Pregnant women with a high risk for Down's syndrome (cutoff > or = 1:250) were taken care of in a special outpatient clinic including procedures like amniocentesis and fetal blood sampling. Amongst 5071 pregnant women, 21 fetal anomalies were seen. Five cases of Down's syndrome, three of trisomy 18, one trisomy 13, two cases of triploidy and four cases of open neural tube defects, one 46 xy/45 x mosaic karyotype and one case of gastroschisis could be diagnosed correctly. One case of trisomy 21, one case of trisomy 18 and two open neural tube defects showed false negative results. Using the cutoff of 1:250 for prenatal detection of Down's syndrome and performing ultrasound routinely to determine gestational age, the sensitivity of the "triple-test" was 83.33% having a specificity of 92.68%. The predictive value of a positive test for prenatal diagnosis of Down's syndrome was 1.33%.(ABSTRACT TRUNCATED AT 250 WORDS)
The thermolabile variant (677TT) of methylenetetrahydrofolate reductase (MTHFR) is a known risk factor for neural tube defects (NTDs). The relationship between a second MTHFR polymorphism (1298A-->C) and NTD risk has been inconsistent between studies. We genotyped 276 complete NTD triads (mother, father and child affected with an NTD) and 256 controls for MTHFR 1298A-->C. Our findings do not support a role for the 1298A-->C polymorphism in NTDs (OR 0.85 (95% CI 0.49-1.47), p= 0.55), nor do we observe a combined effect with the 677C-->T polymorphism.
Effective supplementation with folate, which prevents neural tube defect (NTD) occurrence, and high homocysteine levels in the blood of NTD children's mothers suggest that genes involved in folate and homocysteine metabolism can be involved in NTD aetiology. Genes encoding methylenetetrahydrofolate reductase (MTHFR) or methylenetetrahydrofolate dehydrogenase (MTHFD) belong to the first group. Genes encoding methionine synthase (MTR), its regulator - methionine synthase reductase (MTRR) and also cystathionine synthase (CBS) can be included in the second group. We present a current list of the folate and homocysteine metabolism genes that are known to be involved in NTD and pay special attention to primary and secondary NTD prevention.
Mildly elevated maternal plasma homocysteine (Hcy) levels (hyperhomocysteinemia) have recently been observed in some neural tube defects(NTDs) pregnancies. The aetiology of NTDs is also known to have both genetic and nutritional components. The frequency of two relatively common mutations in the enzyme of cystathionine beta-synthase (CBS), which is one of the main enzymes that controls Hcy level, was examined. Among 76 nonpregnant women in the study, 40 of whom had given birth to infants with NTDs and 36 control women previously had normal offspring. The results showed that no significant difference was found between NTDs mothers and non-NTDs mothers for the frequency of T833-C and the G919-A mutations in the CBS gene. The data suggests that the mother's genotype is not the direct factor involved in the pathogenesis of NTDs.
Mildly elevated maternal plasma homocysteine (Hcy) levels (hyperhomocysteinemia) have recently been observed in some neural tube defect (NTD) pregnancies. Plasma levels of Hcy are governed by both genetic and nutritional factors and the aetiology of NTDs is also known to have both genetic and nutritional components. We therefore examined the frequency of relatively common mutations in the enzyme cystathionine beta-synthase (CBS), which is one of the main enzymes that controls Hcy levels, in the NTD population. Neither the severely dysfunctional G307S CBS allele nor the recently reported 68 bp insertion/I278T CBS allele was observed at increased frequency in the cases relative to controls. We therefore conclude that loss of function CBS alleles do not account for a significant proportion of NTDs in Ireland.
BACKGROUND: We investigated the levels of S100B protein in the serum of patients with neural tube defects (NTD), and the ontogenetic variation on this group of patients. METHODS: Samples from 24 control individuals and 25 patients with NTD were studied. S100B protein levels were determined using LIA-mat Sangtec kit. RESULTS: We observed no difference between the levels of S100B in NTD patients (median 0.860 microg/l) and control individuals (median 0.580 microg/l). When groups were classified according to age, decreased levels were observed in subjects > or = 4 y compared to the younger ones, on the control group; no significant difference was observed when the same comparison is performed on the group of patients with NTD. CONCLUSIONS: This study indicates that the serum concentration of S100B in patients with NTD is similar to that of normal individuals; however, patients with NTD do not show the negative correlation with age which was observed on normal individuals.
Folate administration substantially reduces the risk on neural tube defects (NTD). The interest for a disturbed homocysteine (Hcy) metabolism in relation to NTD was raised by the observation of elevated blood Hcy levels in mothers of a NTD child. This observation resulted in the examination of enzymes involved in the folate dependent Hcy metabolism. This leads to the identification of the first and likely a second genetic risk factor for NTD. The C677T and A1298C mutations in the methylenetetrahydrofolate reductase (MTHFR) gene are associated with an increased risk of NTD and cause elevated Hcy concentrations. These levels can be normalized by an additional folate intake. Thus, a dysfunctional MTHFR partly explains the observed elevated Hcy levels in women with NTD pregnancies, and also in part the protective effect of folate on NTD. Although, the MTHFR polymorphisms are only moderate risk factors, population wide they may account for an important part of the observed NTD prevalence.
Embryos of Ambystoma mexicanum, Xenopus laevis, and Hyperolius viridiflavus taeniatus were exposed to various concentrations of valproic acid (VPA: 0.1, 1.5, 10 mM) from blastula stage (S) 9 on up to advanced gastrulation of control embryos (S 11 1/2-12). At 10 and 5 mM VPA early development was affected in all species tested. However, the most pronounced effects occurred in Ambystoma: the neural folds appeared delayed and showed a flattened and wavy shape; the neural tube was not formed and embryos successively died. In Xenopus and Hyperolius (10, 5 mM VPA) the beginning of gastrulation was delayed up to neurulation of control embryos. In Xenopus many of the embryos completed neurulation, whereas some embryos exposed to 10 mM VPA showed neural tube defects (NTDs) of different type and degree (open neural tube at different regions of the dorsum). In Hyperolius neural folds arose around the blastoporus and fused later on (earlier in embryos treated with 5 mM VPA), but the shape of these embryos was abnormal and the development was not continued (pronounced effect at 10 mM VPA). Comparing the three species, Xenopus proved to be the least sensitive species (at 5 mM VPA 14.2% NTDs of total malformations compared to 100% in the other species). The most sensitive species, Ambystoma, developed head-oedema at 1 mM VPA, whereas the anurans were not affected. Our results suggest a similar mechanism of VPA-induced NTDs in mammals and amphibians.
We have reported previously a 10% aneuploidy detection rate among 39 cases of fetal neural tube defects (NTD). Subsequently we amassed an additional experience of over 17,000 prenatal diagnosis cases over a 5-year period. During this period 106 cases of NTDs were identified; 44 with anencephaly, 62 with open spina bifida. The average maternal age of this population with NTDs was 29 years (15-40); 6 patients declined amniocentesis. Six of 100 cytogenetic studies were aneuploid; one anencephalic fetus had inherited a maternal marker chromosome, and 5 NTD cases had trisomy 18. The average maternal age of the aneuploid cases was 31 (19-40); 3 were 35 years or older. Four of 5 trisomy 18 cases had multiple congenital anomalies (MCA). The overall aneuploidy detection rate in our cohort was 5-6%, while aneuploidy occurred in 2% of the isolated NTD cases, and 24% of the MCA cases. Combining the earlier experience, 4/39 aneuploidy (2 trisomy 18, 4p+, del 13q) yields an aneuploidy detection frequency of 10/145 (7%), of which most (7/10) had trisomy 18. These data support fetal karyotyping for accurate diagnosis, prognosis, and recurrence-risk counseling.
BACKGROUND: Maternal nutritional factors have been implicated in the complex aetiology of neural tube defects (NTD). We investigated whether the amount of weight a woman gained during pregnancy was associated with her risk of delivering an infant with an NTD. METHODS: We conducted a population-based case-control study within the cohort of 708 129 live births and fetal deaths occurring in selected California counties in 1989-1991. Face-to-face interviews were conducted with mothers of 538 (88% of eligible) NTD cases (including those electively terminated, stillborn, or liveborn) and with mothers of 539 (88%) non-malformed liveborn controls within an average of 5 months from the term delivery date. Respondent-reported weight gain during pregnancy (kg) was analysed. Risks of infants having NTD were estimated among women who gained <10 kg compared to those who gained > or =10 kg during > or =38 week gestations. RESULTS: Compared to women who gained > or =10 kg, an increased risk for NTD offspring was observed among women who gained <10 kg (odds ratio [OR] = 3.2, 95% CI : 2.3-4.6). The OR was 5.0 (95% CI : 2.6-9.7) among those women who gained <5 kg during pregnancy. The increased risk was not attributable to maternal non-use of a multivitamin containing folic acid, diabetes, NTD-pregnancy history, age, race/ethnicity, education, gravidity, alcohol use, cigarette use, prepregnant obesity, low socioeconomic status, dieting, nausea, nor to lower dietary intakes of folate, zinc, energy, protein, fat, carbohydrates, and methionine. An increased risk was observed even after simultaneous adjustment for most of these factors (OR = 2.2, 95% CI : 1.2-3.8). The risk associated with gaining <10 kg was greater for anencephaly, but still elevated for spina bifida. CONCLUSIONS: We did not have information on weight gain during early pregnancy. Because weight gain during the relevant embryological period for NTD (first month post-conception) is relatively small and often variable, it seems less likely that elevated NTD risks indicate a causal association between lowered weight gain throughout pregnancy and abnormal development of the neural tube. It seems more likely that lowered weight gain is a consequence of carrying an NTD-affected fetus. However, what this consequence is and why risk was substantially larger for anencephaly is unknown.
Neural tube defects (NTDs) are very serious malformations for the fetus, causing either low life expectancy or a chance of survival only with costly and difficult surgical interventions. In western countries the average prevalence is 1/1000-2000 and in Turkey it is 4/1000. The aim of the study was to characterize ethical approaches at institutional level to the fetus with an NTD and the mother, and the role of health care professionals in four major centers in Turkey. The authors chose perinatology units of four university hospitals and prepared questionnaires for the responsible professionals concerning their own and their institution's ethical approaches to the fetus with an NTD and the mother. The investigation revealed that there were no institutional ethical frameworks or ethics committees available to professional teams in the units. The roles of the health care professionals and their individual decisions and approaches based on ethical principles are described. The ethical decision-making process concerning fetuses with NTDs, examples of institutional approaches to the topic and institutional frameworks, and the role of nurses and other health care professionals are all discussed, based on a literature review. The authors suggest that institutional ethical frameworks, ethics committees, professionals' ethics education and multidisciplinary teamwork should be established for critical situations such as fetuses with an NTD.
At the University Hospital of Groningen maternal serum screening for fetal neural tube defects and Down's syndrome is available to pregnant women on their request. We have inquired into the reasons why women apply for serum screening and how this affects them. We did so by means of questionnaires sent to 200 women and by interviewing 20 women whose screening result indicated an increased chance of giving birth to a Down's syndrome child. The response percentage was 52.5. It appeared that opting for serum screening is seen as a self evident choice rather than a conscious one. In general, at the time of the decision, the women only saw the advantages of the test while possible consequences were often not taken into account. More than 70% of the women said they would apply for amniocentesis if they were told that they had an increased risk of having a baby with Down's syndrome. The confrontation with an increased risk of Down's syndrome then came unexpectedly and caused much distress. How to deal with the risk assessment results proved to be very difficult for these women. The difference in scale of the risk factor as established by the screening test compared with the original risk factor based on maternal age was interpreted by them as being of more significance than the statistical implication of the factor itself.