Antenatal detection of neural tube defects: Comparison of biochemical and immunofluorescence methods

The aim of this study was to determine whether identification of glial cells in amniotic fluid samples could form a useful supplementary test in the antenatal diagnosis of neural tube defects (NTDs). In a 5-year study, 1452 samples of middle trimester amniotic fluid were examined blind to the results of other antenatal diagnostic tests and to the outcome of pregnancy. Reasons for amniocentesis included raised serum alpha-fetoprotein (329), previous NTD (73), and a family history of NTDs (71). Duplicate cytospin preparations were stained with Giemsa and an antibody to glial fibrillary acidic protein (GFAP), and on this basis a prediction of fetal NTD status was made which was not communicated to clinicians. Subsequent management of pregnancies was influenced only by the results of routine antenatal testing for NTDs. Twenty cases of NTDs occurred among the 1406 cases in which the outcome was subsequently known. Of these 20 cases, only five (four anencephalic, one spina bifida) were correctly predicted by immunofluorescent identification of GFAP-positive cells in the amniotic fluid. The remaining 15 cases (two anencephalic, 13 spina bifida) were not so identified. In a further 18 cases, apparently GFAP-positive cells were identified in the absence of NTDs. We conclude that GFAP immunofluorescence examination of routine amniocentesis samples of amniotic fluid is not a useful predictive test for NTDs.     

The early diagnosis of neural tube defects

The sonographic diagnosis of fetal neural tube defects (NTDs) has been enhanced by the recognition of associated brain and skull anomalies. Previous reports have found these anomalies to be accurate in predicting spina bifida after 16 weeks' gestation, and an inverse correlation was suggested between the presence of these sonographic markers and gestational age. Therefore, we assumed that early second-trimester sonography would be at least as accurate as that performed after 16 weeks' gestation. To examine this hypothesis, we looked for the presence of these cranial sonographic markers suggestive of open NTDs in 8011 low-risk cases, using transvaginal sonography (TVS), between the 12th and 17th week of gestation (menstrual age). Fetal NTDs were identified in ten cases (l.25%o). The NTDs were cervico-cranial in three, lumbo-sacral in six, and thoracal in one of the ten cases. None of the seven cases examined was dyskaryotic. Cerebellar dysmorphism, ‘banana’ sign, cerebellar absence, and hypoplasia were detected in all the low NTDs, usually before the detection of the spinal lesion. All the sonographically diagnosed malformations were confirmed by post-abortal examination except in one case, where the patient decided to continue the pregnancy and refused follow-up. We therefore conclude that transvaginal sonographic examination of the fetal skull before the 17th week of gestation is an accurate method for the detection of low NTDs.     

Approaches to studying the genomic architecture of complex birth defects

Every year nearly 6 percent of children worldwide are born with a serious congenital malformation, resulting in death or lifelong disability. In the United States, birth defects remain one of the leading causes of infant mortality. Among the common structural congenital defects are conditions known as neural tube defects (NTDs). These are a class of malformation of the brain and spinal cord where the neural tube fails to close during the neurulation. Although NTDs remain among the most pervasive and debilitating of all human developmental anomalies, there is insufficient understanding of their etiology. Previous studies have proposed that complex birth defects like NTDs are likely omnigenic, involving interconnected gene regulatory networks with associated signals throughout the genome. Advances in technologies have allowed researchers to more critically investigate regulatory gene networks in ever increasing detail, informing our understanding of the genetic basis of NTDs. Employing a systematic analysis of these complex birth defects using massively parallel DNA sequencing with stringent bioinformatic algorithms, it is possible to approach a greater level of understanding of the genomic architecture underlying NTDs. Herein, we present a brief overview of different approaches undertaken in our laboratory to dissect out the genetics of susceptibility to NTDs. This involves the use of mouse models to identify candidate genes, as well as large scale whole genome/whole exome (WGS/WES) studies to interrogate the genomic landscape of NTDs. The goal of this research is to elucidate the gene-environment interactions contributing to NTDs, thus encouraging global research efforts in their prevention.     

土壤性质在出生缺陷环境风险中的指示作用

为研究土壤性质在出生缺陷环境风险中的指示作用,考虑了区域人口分布和疾病空间结构,使用Bayesian方法,对山西省和顺县连续4年的神经管畸形发生的数据进行了处理,并使用非参数统计的方法,结合土壤环境过程机理,对土壤的理化性质和出生缺陷的环境风险做了系统分析. 结果表明:土壤的机械组成,阳离子交换量(CEC),pH,有机质含量及碳酸钙含量都与神经管畸形发生率显著相关. 土壤砂粒含量高的地区,神经管畸形发生的风险会显著增加;土壤粘粒含量高的地区,神经管畸形发生的风险会显著降低. 土壤阳离子交换量高的地区,神经管畸形发生的风险会显著降低. 在偏碱性土壤且pH较高的地区,神经管畸形发生的风险会显著降低.在有利于土壤提供有效形态重金属及稀土元素的环境条件下,神经管畸形发生率会显著提高.在影响神经管畸形发生的环境因素中,土壤介质中各形态元素的有效含量比其总量具有更强的指示作用.      

Open fetal surgery for myelomeningocele

Despite efforts at prevention through the use of preconception folic acid, spina bifida remains one of the most common congenital anomalies of the central nervous system that is compatible with life. It is, however, associated with a significant degree of lifelong morbidity. The development of open fetal surgery for myelomeningocele (MMC) has been a long process but one that serves as a model for how new procedures and technologies need to be properly evaluated before being brought into mainstream medical practice. Even so, risks and benefits need to be evaluated for each patient. The currently available studies have been carried out on a highly selected patient population where the fetal findings provided the maximum opportunity for benefit from prenatal closure of the MMC defect. There is the potential that as the surgery becomes more widely available, pressure will be brought to bear to perform surgery in cases where the likelihood for benefit is decreased and yet the risks are not. The only way to duplicate the results of the current studies is to follow the methodology and criteria that were used in the studies. This will mean that not every fetus with an MMC will be a candidate for in utero surgery. The balance of risk to benefit will continue to evolve as further technological advances are evaluated and more follow-up information is obtained. Copyright © 2011 John Wiley & Sons, Ltd.     

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 ≥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 (≥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.     

Vitamins,folic acid and neural tube defects: Comments on investigations in the United States

No clear answer concerning whether multivitamin/folate supplementation prevents neural tube defects (NTDs) is provided by three studies in the United States. All these studies are occurrence in nature, no recurrence studies having been conducted. The Atlanta Birth Defects Study is subject to pronounced memory and recall biases, the length between event and interview being as long as 16 years. In a second study (Boston University), objections can be raised to certain aspects of the experimental design, and the claim that 22 per cent of women started vitamins sufficiently early after pregnancy diagnosis to influence NTD formation is suspicious. Our NICHD case control study of 541 women in California and Illinois revealed no evidence for multivitamins or folic acid preventing NTDs. U.S. public policy-makers face difficulties in applying results of recurrence or occurrence studies in high-risk areas to low-risk areas in the U.S.     

Fetal therapy: practical ethical considerations

Progress in prenatal diagnosis can lead to the diagnosis of severe fetal abnormalities for which natural history anticipates a fatal outcome or the development of severe disability despite optimal postnatal care. Intrauterine therapy can be offered in these selected cases. Prenatal diagnosis is the only field of medicine in which termination is an option in the management of severe diseases. Fetal therapy has therefore developed as an alternative to fatalist expectant prenatal management as well as to termination of pregnancy (TOP). There are few standards of fetal care that have gone beyond the stage of equipoise and even fewer have been established based on appropriate studies comparing pre- and postnatal care. Several ethical questions are being raised as fetal surgery develops, including basic Hippocratic principles of patients' autonomy and doctors' duty of competence moving the boundaries between experimental surgery, therapeutic innovation and standard care. In addition, the technical success of a fetal intervention can only rarely fully predict the postnatal outcome. Managing uncertainty regarding long-term morbidity and the possibility for fetal therapy to change the risk of perinatal death into that of severe handicap remains a critical factor affecting women's choice for TOP as an alternative to fetal therapy. Copyright © 2011 John Wiley & Sons, Ltd.     

Serum alpha-fetoprotein and neural tube defects in the first trimester of pregnancy

As part of the Medical Research Council randomized trial of vitamin supplementation in the prevention of neural tube defects (NTDs), maternal serum alpha-fetoprotein (AFP) was available for 19 NTD pregnancies. Each of these was matched with four unaffected controls, by maternal age, participating centre, and duration of sample storage. The samples came from women whose gestational age ranged from 6 to 14 completed weeks. The median AFP level in the affected pregnancies was 1·2 multiples of the median value in unaffected pregnancies of the same gestational age (95 per cent confidence interval (CI) 0·83–1·59). This confirmed the view that serum AFP measurement is of no practical value in the detection of NTDs in the first trimester of pregnancy. The study also showed that folic acid supplementation, used as a method of preventing NTDs, had no effect on the concentrations of maternal serum AFP up to 14 weeks of pregnancy.     

A prospective study of amniotic fluid cholinesterases: Comparison of quantitative and qualitative methods for the detection of open neural tube defects

The value of quantitative and qualitative methods of cholinesterase (ChE) analysis in the detection of open neural tube defect (NTD) has been assessed in a prospective survey of 1495 mid-trimester amniotic fluids. Using a quantitative method the mean ChE values were much lower in fluids from pregnancies of normal outcome but it was not possible to discriminate these fluids completely from those associated with NTD pregnancies. particularly when the specimens were contaminated with blood. Similarly, measurement of acetylcholinesterase (AChE) activity alone by three different methods also failed to eliminate the overlap between the two groups. In contrast, polyacrylamide gel electrophoresis revealed only a single band of ChE activity in 1408 out of 1410 fluids from pregnancies with a normal outcome whilst amniotic fluids from all 60 cases of open NTD. 6 out of 7 cases of exomphalos and 3 out of 4 cases of intra-uterine death gave the characteristic second faster-running AChE band. A qualitative gel method which requires the same amount of ChE activity to be loaded from each amniotic fluid is an effective method for pre-natal diagnosis of NTDs.     

Prenatal diagnosis: does it alter outcome?

The prenatal detection of urinary tract anomalies is changing paediatric practice but in many areas the impact on clinical outcome remains difficult to quantify. However it is already apparent that termination of pregnancy has reduced the numbers of infants with lethal pulmonary hypoplasia and renal dsyplasia who would previously have been liveborn but destined to succumb as neonates. Similarly, referrals of major non lethal abnormalities such as bladder exstrophy are declining as parents increasingly opt for termination. Fetuses at greatest risk of early onset postnatal renal failure can now be identified with considerable accuracy on prenatal ultrasound. Termination, prompted by quality of life considerations, could result in reduced numbers of infants and young children requiring end stage renal failure treatment in the first few years of life. Pre natal detection of anomalies such as PUJ obstruction and reflux undoubtedly provides an opportunity to avert functional deterioration and minimise urinary infection. But the proportion of children who genuinely benefit has proved difficult to assess. The prenatal detection of mild dilatation is of doubtful benefit in all but a minority of cases. Clinically significant underlying pathology is rare yet this common prenatal finding often generates disproportionate parental anxiety. Copyright © 2001 John Wiley & Sons, Ltd.     

Neural tube defects in the sample of genetic counselling

Objective This study was conducted to evaluate the major demographic details, diagnostical and clinical features, as well as the risk of recurrence of cases with the major types of neural tube defects (NTD). We also examined the efficiency of ultrasonography based on autopsy examinations during 26 years. Methods The investigations were made into the sample of 743 NTD diagnosed between 1 January 1976 and 31 December 2002. A computerized database was used to sum up the available information about the individual cases; in addition to surveying the couples' major demographic details, we also had the opportunity to collect detailed information about the history, diagnostics (ultrasound) and outcome of the pregnancies as well as the results of the autopsies during the investigation. Results In the 743 cases of NTD, maternal and paternal median ages turned out to be 23.7 years (±5.22 years) and 28.7 years (±5.81 years), respectively. The male:female ratio was 0.78. Comparable samples of anencephaly and spina bifida allowed for the conclusion that a positive genetic history was equally often found while a positive obstetrical history was almost twice as common in anencephaly. The sensitivity of the maternal serum-alpha fetoprotein (AFP) screening test is the highest in anencephaly and lowest in encephalocele. While the majority of cases of anencephaly were diagnosed before the 24th gestational week, examples of diagnosing spina bifida and encephalocele at a later time could also be found. Among the associated malformations other than those of the central nervous system special mentioning should be made of fetal pyelectasia, cleft palate as well as diaphragmatic herniation. No pathological karyotypes were found in association with encephalocele or spina bifida, but anencephaly was accompanied with trisomy 21 and trisomy 18 in one case each. Anencephaly was found to have the highest risk of recurrence in both nervous system malformations and malformations other than those of the nervous system. Sonography proved to be the most reliable method in cases of enecephalocele. Conclusion The respective median values of maternal and paternal age show that aetas has no role in the occurrence of NTDs. NTDs are more common among girls. Positive genetic, obstetrical and medical findings are of great importance in the incidence of NTDs. Although reliable to only a limited extent, maternal serum-AFP tests are considered to be useful and necessary in screening NTDs, while sonography is the gold standard method in recognizing these frequent malformations. The knowledge of the eventual associated malformations is mainly important in certain cases of spina bifida, which may also yield a good post-natal prognosis. Our data obtained from the sample of 26 years also confirm that the periconceptional administration of folic acid reduces the incidence and risk of recurrence of NTDs. Copyright © 2007 John Wiley & Sons, Ltd.     

The behaviour of maintenance and the intensive husbandry of cattle,sheep and pigs

A major feature of our living environment consists of the domesticated animals. As their use intensifies so too does the obligation to them — and to their basic life practices — which we acquired at the moment of their domestication. Much of the behaviour of farm animals is concerned with self-maintenance, indeed, highly successful self-maintenance is the basis of animal productivity. Activities involved in such maintenance appear to fall into eight primary categories. These are basically of innate origin and include much instinctive behaviour. The use of these behaviours of reactivity, ingestion, exploration, movement, association, body care, territorialism and rest are vital to the animal in its integration and mediation with its environment. Within these eight primary systems of behaviour, numerous specific behaviours are exhibited in natural free-ranging conditions. Cattle exhibit 44 specific behaviours related to maintenance; sheep have 43 and pigs show 48. All of these above behaviours require environmental facility and where this is deficient, deficits occur in behaviour.Ethological deficits have been determined for methods of husbandry relating to the intensive production of calves, steers, sheep and pigs. Veal calves had 25 behavioural deficits, feedlot cattle had 11, housed sheep had 13 and enstalled swine had 26. These figures give indices of behavioural deprivation ranging from 25% in feedlot cattle to 56% in veal calves in stalls.Anomalous behaviour is now increasingly seen among animals which are managed under close confinement; restricted accommodation in an essentially featureles environment. Much of the anomalous behaviour which has been investigated is found to be the result of aversive environments. Anomalous behaviours are typically found in those forms of husbandry which involve intense grouping of animals and also a lack of what might be termed diversionary facilities in their environment. Reduced input of environmental stimulation and opportunity is evidently capable of acting with adverse effect on functional mediation, so as to generate anomalous forms of behaviour such as “orosthenia” — pathological oral activity. Such abnormal behaviour serves as a symptom of confinement stress. In animal production the application of ethology can provide a monitoring operation for livestock care to ensure welfare and ethological entitlement.     

Cystic lung lesions – prenatal diagnosis and management

With increasing use of fetal ultrasound comes an increase in the detection of clinically silent ‘abnormalities’ which pose diagnostic and management dilemmas for perinatologists and paediatricians. Congenital thoracic malformations (CTMs) (excluding congenital diaphragmatic hernia) are one such example, where a few cases are symptomatic in early life and management options are clear, but the majority are clinically asymptomatic, giving rise to difficulties in defining postnatal management of the well child with a sonographic or radiological lesion. Here, we will outline the prenatal presentation and natural history of CTMs that are not congenital diaphragmatic herniae and briefly discuss the approach to postnatal management, which is covered in more detail in the review by Laje and Liechty in this issue. Copyright © 2008 John Wiley & Sons, Ltd.     

The value and limitations of using predetermined criteria in decision making for maternal-fetal interventions

Maternal-fetal interventions—such as prenatal fetal myelomeningocele (MMC) repair—are at the forefront of clinical innovation within maternal-fetal medicine, pediatric surgery, and neonatology. Many centers determine eligibility for innovative procedures using pre-determined inclusion and exclusion criteria based on seminal studies, for example, the “Management of Myelomeningocele Study” for prenatal MMC repair. What if a person's clinical presentation does not conform to predetermined criteria for maternal-fetal intervention? Does changing criteria on a case-by-case basis (i.e., ad hoc) constitute an innovation in practice and flexible personalized care or transgression of commonly held standards with potential negative consequences? We outline principle-based, bioethically justified answers to these questions using fetal MMC repair as an example. We pay special attention to the historical origins of inclusion and exclusion criteria, risks and benefits to the pregnant person and the fetus, and team dynamics. We include recommendations for maternal-fetal centers facing these questions.     

Prenatal diagnosis and management of twin pregnancies complicated by a co-existing molar pregnancy

Recent advances in ultrasound and molecular genetics have increased our understanding and hence enhanced the perinatal management of complete and partial hydatidiform mole. By contrast, the management of a twin pregnancy combining a normal pregnancy with a normal fetus and a complete hydatidiform mole (CHM) remains complex and controversial due to conflicting data from different parts of the world. The aim of this review is to analyse the international literature on twin pregnancies that include a mole, present the complications and outcome of pregnancy and to discuss the perinatal management. Management is complicated and women should be counselled about the maternal and fetal complications, and the pregnancy monitored carefully by a perinatal team with experience in high-risk obstetrics and access to neonatal care. The data reviewed here suggest that a woman who decides to continue with the pregnancy including a CHM must be aware that, overall, she only has a one in four chance of live birth and in around 35% of cases she will develop persistent trophoblastic disease (PTD) after delivery. In ongoing pregnancies, there will be, in at least 20% of the cases, an early onset of pre-eclampsia (PET) and a 29% risk of fetal loss due to late miscarriage, intrauterine death and neonatal death. Maternal serum human chorionic gonadotrophin (MShCG) could be useful in predicting outcome in twin pregnancy combining normal pregnancy and CHM, but this needs to be investigated prospectively. Copyright © 2005 John Wiley & Sons, Ltd.     

Prenatal testing for Imprinting Disorders: A clinical perspective

Imprinting Disorders (ImpDis) are a group of congenital conditions caused by aberrant imprinting resulting in disturbed expression of parentally imprinted genes. ImpDis are rarely associated with major malformations, but pre- and/or postnatal growth and nutrition are often affected. In some ImpDis, behavioral, developmental, metabolic and neurological symptoms might present in the perinatal context or later in life, and in single ImpDis, there is a higher risk of tumors in childhood. Prognosis depends in part on the molecular cause of each ImpDis, but due to high clinical variability and (epi)genetic mosaicism, predicting the clinical outcome of a pregnancy solely based on the underlying molecular disturbance is difficult. Therefore, interdisciplinary care and treatment approaches play an important role in the management and decision making of affected pregnancies, especially taking into account fetal imaging in addition to genetic findings. Prenatal findings influence perinatal management, and thereby improve the prognosis of ImpDis associated with severe but sometimes transient clinical complications in the neonatal period. Therefore, prenatal diagnosis can be crucial for appropriate management not only to the pregnancy itself but might also have a life-long effect.     

Increased maternal serum alpha-fetoprotein and human chorionic gonadotropin in compromised pregnancies other than for neural tube defects or Down syndrome

Intrauterine fetal death occurred in four women who were ‘screen-positive’ in a screening programme for neural tube defects (NTDs) and Down syndrome (DS). These women had very high levels of maternal serum alpha-fetoprotein (MSAFP) and maternal serum human chorionic gonadotropin (MShCG). Therefore, we evaluated all ‘screen-positive’ women in whom both of these markers were ⩾ 2.0 multiples of the median. The cases fulfilling these criteria totalled 11, and only one of them had no complications. High concentrations of both MSAFP and MShCG in a number of these cases might have been caused by an increased placental volume, which, in turn, might have been induced by decreased perfusion of the placenta. We conclude that screening programmes wrongly determine a high risk of fetal NTD or DS if the concentrations of both these parameters are very high. Invasive diagnostic procedures should be avoided in these cases, particularly in view of the increased risk of an adverse pregnancy outcome.     

Is maternal alpha-fetoprotein screening still of value in a low-risk area for neural tube defects?

Estimation of maternal serum alpha-fetoprotein (AFP) was used as a screening method for the detection of neural tube defects (NTDs) in 6344 women over three years. Of 88 (1.4 per cent) who had one or more serum AFP levels equal to, or greater than, 2.5 multiples of the median (MoM) for the relevant gestational age, 43 (0.68 per cent) underwent amniocentesis. There were eight NTDs. Four of these were screened by serum AFP, and all cases of spina bifida had serum AFP levels greater than 3.0 MoM, including one small open defect which was not seen on ultrasound. The other four cases of NTD, which were not screened, were identified by ultrasound. Of 64 singleton pregnancies 32 (50 per cent) had serum AFP levels between 2.5 and 3.0 MoM, and low birthweight (⪕2500 g) occurred in 29 per cent. Because of improvements in ultrasound techniques and the apparent falling incidence of NTD, the role of serum AFP as the primary screening procedure should be regularly reviewed. Effective screening is dependent on mothers booking early.     

Postnatal management of prenatally diagnosed abdominal masses and anomalies

Rapid advancement in fetal diagnostic imaging has increased our ability to diagnose a multitude of anomalies in the prenatal period. The purpose of this chapter is to review our current understanding of prenatally diagnosed intra-abdominal lesions, and describe the current guidelines for the postnatal management and subsequent outcome for these lesions. Copyright © 2008 John Wiley & Sons, Ltd.