Increased frequency of neural tube defects in sibs of children with other malformations

A non-coding insertional mutation of Grhl2 causes gene over-expression and multiple structural anomalies including cleft palate, spina bifida and encephalocele

Orofacial clefts, including cleft lip and palate (CL/P) and neural tube defects (NTDs) are among the most common congenital anomalies, but knowledge of the genetic basis of these conditions remains incomplete. The extent to which genetic risk factors are shared between CL/P, NTDs and related anomalies is also unclear. While identification of causative genes has largely focused on coding and loss of function mutations, it is hypothesized that regulatory mutations account for a portion of the unidentified heritability. We found that excess expression of Grainyhead-like 2 (Grhl2) causes not only spinal NTDs in Axial defects (Axd) mice but also multiple additional defects affecting the cranial region. These include orofacial clefts comprising midline cleft lip and palate and abnormalities of the craniofacial bones and frontal and/or basal encephalocele, in which brain tissue herniates through the cranium or into the nasal cavity. To investigate the causative mutation in the Grhl2Axd strain, whole genome sequencing identified an approximately 4 kb LTR retrotransposon insertion that disrupts the non-coding regulatory region, lying approximately 300 base pairs upstream of the 5' UTR. This insertion also lies within a predicted long non-coding RNA, oriented on the reverse strand, which like Grhl2 is over-expressed in Axd (Grhl2Axd) homozygous mutant embryos. Initial analysis of the GRHL2 upstream region in individuals with NTDs or cleft palate revealed rare or novel variants in a small number of cases. We hypothesize that mutations affecting the regulation of GRHL2 may contribute to craniofacial anomalies and NTDs in humans.

Three generations of matrilineal excess of birth defects in Irish families with neural tube defects

BACKGROUND

Neural tube defects (NTDs) and birth defects overall are more likely to occur among maternal compared to paternal relatives in two generations (uncles/aunts and first cousins) of Irish families where an individual has been born with an NTD.

AIMS

The aim of this study was to determine if the matrilineal excess persisted into the third generation.

METHODS

First cousins were interviewed about their pregnancy outcomes and their offsprings' health.

RESULTS

Maternal first cousins once removed (FCOR) were more likely to have birth defects than paternal FCOR: 6.7 versus 3.5% (adjusted odds ratio 1.49, 95% CI 0.57, 3.89). No NTDs occurred. Folic acid supplementation significantly reduced the risk of birth defects (P = 0.04).

CONCLUSIONS

This study demonstrates an excess of birth defects among maternal relatives in three consecutive generations of NTD families, and supports the hypothesis that an underlying mechanism links distant maternal relatives in at least some NTD families.

Birth defects in uncles and aunts from Irish families with neural tube defects

BACKGROUND

Previous studies suggested an excess of matrilineal cases of neural tube defects among distant relatives in NTD families. There is little information on patterns of heredity of other birth defects among distant relatives.

METHODS

Between 1995 and 2003, 78 nuclear families and 373 uncles and aunts were interviewed about birth defects among uncles and aunts in Irish families with an NTD.

RESULTS

Among 783 total uncles and aunts, those related through the mother had more birth defects overall than those related through the father (8.4 vs. 4.0%, p = 0.01). The excess persisted after controlling with logistic regression models for maternal and paternal age, gender of uncle/aunt, proband's NTD diagnosis, and year of birth (OR 2.52; 95% CI: 1.29, 4.91; p = 0.007). Among individual birth defects, significant excesses over expected rates were seen for spina bifida, congenital heart defects, and syndactyly.

CONCLUSIONS

This study of reported birth defects suggests that maternal uncles and aunts in Irish families have significantly more birth defects than paternal uncles and aunts. These results, if confirmed, support the hypothesis that NTD relatives carry a susceptibility to other birth defects, preferentially on the mother's side of the family, suggesting opportunities for prevention. Birth Defects Research (Part A) 2008.

Nonsyndromic cleft lip and palate is not associated with cancer or other birth defects

Nonsyndromic cleft lip with or without cleft palate (NSCLP) is one of the most common human malformations with an average prevalence of 1 in 1,000 live births. The cause(s) of NSCLP remain unclear as the relative roles of genes, of the environment, and/or of chance alone are unknown. The purpose of this study was to evaluate the potential role of environmental factors in the cause of NSCLP, to determine if other birth defects aggregate in families with at least one individual affected with NSCLP, and to investigate the frequency of cancer in the first- and second-degree relatives of NSCLP index-cases. Included in this study were 196 index-cases and their families. Information pertaining to environmental factors and pedigree information was obtained on each family. Analysis showed that no single environmental factor could explain the occurrence of NSCLP in this population. The frequency of other birth defects in these families was 1.2%, which is not increased over that in the general population. One hundred seven cancers were reported in 72 of the 196 families included in the study. The frequency of cancer was not significantly increased in the first- or second-degree relatives of the NSCLP index cases or in those families with a positive family history of NSCLP. No childhood or adult cancers were reported in any of the 196 NSCLP index cases.

Does periconceptional multivitamin use reduce the risk of neural tube defects associated with other birth defects? data from two population-based case-control studies

The role of periconceptional folic acid in the prevention of neural tube defects (NTDs) is well established. However, it is not clear whether a protective effect exists for the subset of nonsyndromic NTD with other "unrelated" major structural birth defects (NTD-multiples). This question is important to investigate because of shared pathogenetic mechanisms between NTD and other types of birth defects, and because of the epidemiologic differences that have been shown between NTD-multiples and NTD-singles. We analyzed data from two population-based case-control studies of NTDs, Atlanta 1968-1980, and California 1989-1991, to assess whether periconceptional multivitamin use reduces the risk of NTD-multiples. Maternal vitamin histories were assessed for 47 and 65 NTD-multiples cases and 3,029 and 539 control babies in Atlanta, and California, respectively. There was a substantial risk reduction associated with periconceptional multivitamin use (-3 to +3 months) for NTD-multiples (pooled odds ratio = 0.36, 95% C.I. 0.18-0.72) that persisted after adjustment for maternal race/ethnicity and education. Also, no specific types of NTDs or NTDs with specific defects explained the risk reduction with vitamin use. These data suggest that multivitamins reduce the risk of nonsyndromic NTD cases associated with other major birth defects. The implication of this finding for the role of vitamins in the prevention of non-NTD birth defects should be further explored.

A population-based study of the risk of recurrence of birth defects

BACKGROUND

Certain birth defects are known to recur in families, but most estimates of the risk of recurrence have come from clinic-based studies. In this study we estimated the risk of recurrent birth defects using a population-based registry.

METHODS

The study was based on the records of the first and second infants delivered by 371,933 women from 1967 through 1989. The records are maintained by the Medical Birth Registry of Norway. For the 9192 women whose first infant had a birth defect, we determined the relative risk of similar and dissimilar defects in the second infant. The reference population was women whose first infant had no defect.

RESULTS

Among first infants, 2.5 percent had a birth defect. The mothers of affected first infants were 2.4 times as likely as other women to have second infants with any registered defect. This increased risk was due primarily to an increased (7.6 times higher) risk of the same defect in the second infant as in the first (95 percent confidence interval, 6.5 to 8.8) and secondarily to a slightly increased (1.5 times higher) risk of a different defect in the second infant (95 percent confidence interval, 1.3 to 1.7). Among the women who lived in the same municipality during both pregnancies, the relative risk of having a second infant with the same defect was 11.6, as compared with 5.1 among the women who moved to another municipality after the birth of their first infant (P < 0.001).

CONCLUSIONS

Among women whose first infant has a birth defect, the risk of the same defect in the second infant is substantially increased and the risk of a different defect in the second infant is slightly increased. Environment plays a strong part in repeated defects.

Familial occurrence of agonadism and multiple internal malformations in phenotypically normal girls with 46,XY and 46,XX karyotypes, respectively: a new autosomal recessive syndrome

We report on 2 phenotypic sisters, one with 46,XY; the other with 46,XX. The 2 girls had similar related internal malformations, including agonadism, hypoplasia of the right pulmonary artery, hypoplasia of the right lung, isolated dextrocardia with complex vitium cordis, and diaphragmatic hernia (only sib 1) or omphalocele (only sib 2). This combination of malformations did not fit into any of the previously described syndromes. For this syndrome we suggest the acronym PAGOD ([hypoplasia of the] pulmo, and pulmonary artery, agonadism, omphalocele/diaphragmatic defect, dextrocardia). The occurrence of a basically similar set of malformations in 2 unlike sex is interpreted as evidence for autosomal recessive inheritance. The different gonosomal status excludes the Y chromosome as a responsible factor. The peculiar finding of a 46,XX sex chromosome constitution combined with agonadism and an intact urogenitral tract emphasizes the concept of secondary regression of Wolffian and Müllerian structures. The associated malformations of mesodermal structures can be interpreted as midline defects. We suggest that, from the developmental field perspective, secondary regression of midline structures including the gonadal anlage explains the pathogenesis reasonably well.

An international collaborative study of the epidemiology of esophageal atresia or stenosis

Epidemiologic data were analyzed for a total of 2,693 infants with esophageal atresia registered in nine congenital malformation registries around the world. The average recorded prevalence at birth was 2.6 per 10,000 births, with a significant variability among programs--and sometimes within a program--and a maximum prevalence of above 3 per 10,000 births. Clusters of infants with esophageal atresia were observed but may be random. An increasing rate was seen during the period 1965 to 1975 (Norway, South America, Sweden). The type of esophageal atresia was specified in only 439 cases, but no major differences were seen in the epidemiologic characteristics of infants with the most common type (distal fistula) and infants with other types. There was an excess of low birth weight and preterm birth, and infants with esophageal atresia had a birth weight 500 to 1,000 g less than normal infants in each gestational week. There was an excess of twins, apparently mainly or exclusively due to monozygotic twinning, but in only two pairs did both twins have esophageal atresia. There was no effect seen of maternal age, but low parity, irrespective of maternal age, was associated with an increased risk for esophageal atresia. Infant survival varied among programs and depended heavily on associated malformations. Among 1,107 sibs born before the proband and 385 born after the proband, only 25 (1.7%) had a serious malformation; three had esophageal atresia. In 57.3% of the infants with esophageal atresia, no other malformations were present, in 36.4% other major malformations were recorded, and in 6.3% there were chromosomal anomalies. The malformations present associated with esophageal atresia were analyzed: a large proportion entered the constellation sometimes called "caudal mesoderm spectrum of malformations": VATER, Potter, and caudal regression sequences.

Genetic-epidemiologic study of omphalocele and gastroschisis: evidence for heterogeneity

On the basis of clinical manifestations, epidemiologic characteristics, and the presence of additional malformations, omphalocele (OM) and gastroschisis (GA) are considered casually and pathogenetically distinct abdominal wall defects. More than 50% of infants with OM have additional defects, but only about 15% of those with GA do. To evaluate whether there is heterogeneity between isolated and multiply affected cases of OM and GA, we analyzed epidemiologic characteristics and familial risks of major defects for 82 OM and 81 GA cases drawn from a population-based study in the Maryland-Washington, DC-Northern Virginia area and born from 1980 through June 1987. We examined year of birth, sex, race, and maternal age distributions after stratifying the infants into isolated and multiple defect groups. We found significant differences in maternal age between cases with isolated OM and GA, but not between cases with GA or OM who had other defects. Using regressive logistic models, we analyzed familial aggregation of birth defects among relatives of infants with OM and GA. An autosomal recessive model of inheritance was found to be the most parsimonious explanation for the families of infants with isolated OM or GA. However, for families of infants with multiple defects, a sporadic or nongenetic model fit best. These findings are not only useful for estimating familial risk of major birth defects, but they also suggest further heterogeneity of infants with OM and GA according to the presence of other malformations.

Dietary folate and nonneural midline birth defects: no evidence of an association from a case-control study in Western Australia

In a population-based case-control study of dietary folate and neural tube defects, information was collected by interview and self-administered questionnaires from the mothers of cases with only neural tube defects, from the mothers of matched control infants with defects other than neural tube defects, and from the mothers of matched live-born infants with no birth defects. The association of midline birth defects (excluding neural tube defects) with dietary folate intake in the first 6 weeks of pregnancy was assessed by restricting the analysis to the 59 mothers of infants with midline defects in the first control group and comparing them with their matched control infants in the second control group. The crude and adjusted odds ratios for dietary folate and for folic acid supplementation were close to one, and all confidence intervals embraced unity. These data do not provide evidence of an association between midline birth defects (excluding neural tube defects) and either dietary folate or folic acid supplementation.

Clustering of malformations in the families of South American oral cleft neonates

The relatives of 741 newborn children with non-syndromic cleft lip with or without cleft palate (CL +/- P), of 115 with isolated cleft palate (CP), and of equal numbers of appropriate controls were screened for the presence of the same or different malformations. The main findings were as follows. (1) The frequency of familial cases of CL +/- P (17.3%) was much higher than the prevalence of this malformation among the relatives of controls (0.5%). (2) The sibs of CL +/- P subjects showed a higher prevalence of this condition than their parents (2.9% v 1.6%). (3) The degree of genetic determination of this condition should be high (70 to 74%), and the data in general favour a multifactorial model of inheritance, with different thresholds between sexes. However, the action of dominant genes cannot be excluded since selection or dominant genes or both could be postulated to explain the parent/sib difference. (4) The frequency of other malformations was also significantly raised in the families of CL +/- P probands, as compared to controls (12.1% v 6.2%). (5) The prevalence of these other malformations was higher among sibs (1.6%) than parents (0.7%) of CL +/- P babies. (6) A general susceptibility to malformations and different exposure to selective agents may explain these latter findings. (7) None of the comparisons involving CP children yielded significant results.

Familial congenital diaphragmatic defect and associated midline anomalies: further evidence for an X-linked midline gene?

We report on familial occurrence of congenital diaphragmatic defect and associated midline anomalies, namely cleft palate and omphalocele in brothers. This family further supports the existence of an X-linked gene involved in the organization of the embryonal midline. This particular mutant gene might be active in the schisis-morphogenesis phenomena occurring at the midline.

Reproductive behaviour and consistent patterns of abnormality in offspring of Vietnam veterans

In view of the persistent claim of Australian Vietnam veterans that their health and that of their children were adversely affected, aspects of reproductive behaviour and the distribution of disease and disability in family units were investigated in a sample of Tasmanian veterans and another group chosen for comparison of selected characteristics. One third of veterans reported serious health problems and their reproductive behaviour differed with more marital breakdowns, increased use of reproductive alternatives, and more complications of pregnancy. Patterns of malformation and disease among veterans' children involved predominantly the central nervous, skeletal, and cardiovascular systems. A similar pattern was detected on review of the three other major investigations on veterans' offspring in the USA and Australia. Although plausible mechanisms remain unknown, the evidence from all available studies supports a causal contribution to defects in veterans' children from a paternally mediated genetic effect.

Twinning, nonrighthandedness, and fusion malformations: evidence for heritable causal elements held in common

Certain relatively common congenital malformations that are reported to be excessive in frequency among twins are also found in excess among first-degree relatives of twins. They are familially associated with each other. Like twinning, they are familially associated with nonrighthandedness (NRH). They also share the fact that they affect structures that are built by the fusion of bilateral embryonic halves and then remodeled under the influence of neural crest mesenchyme. This conjunction of associations suggests that twinning, NRH, and the fusion malformations share causal elements, some of which may be heritable. Determination of spatial relationships in embryogenesis ("embryonic body symmetry determination") and the functions of neural crest mesenchyme may be mechanisms unifying these effects.

Genetic aspects of early childhood scoliosis

Eighty-seven families with early onset scoliosis were evaluated. These were divided into 3 groups: resolving infantile idiopathic scoliosis (15 families), progressive infantile idiopathic scoliosis (21 families), and congenital scoliosis due to vertebral malformations (51 families). The children with congenital scoliosis were subdivided into those who had closed neural arch defects (19 families) and those who did not (32 families). Resolving infantile idiopathic scoliosis was usually associated with plagiocephaly, and both deformations tended to show spontaneous recovery. These children were otherwise normal. Seven (33%) of the children with progressive infantile idiopathic scoliosis were mentally retarded, but only 2 had a congenital malformation. In contrast, 18 (33%) of the children with congenital scoliosis had other malformations, but only 2 were mentally retarded. The recurrence risk for scoliosis was low in each group studied. However, there was an increased risk (4% for sibs) of neural tube defects in the families with congenital scoliosis (with or without neural arch defects). This sib risk was apparent for probands with only a single hemivertebrum in addition to probands with more extensive vertebral defects and would support an etiological relationship between neural tube defects and other vertebral malformations.

Studies in neural tube defects. I. Epidemiologic and etiologic aspects

In the NIH Collaborative Perinatal Project, a prospective study of over 53,000 pregnant women and their offspring, 71 single-born children (13.33/10,000) were found to have a non-syndromal neural tube defect (NTD). A family history was present in only one case. The group of individuals with NTD was compared to a group of 400 randomly selected non-malformed control infants. Of over 50 maternal factors studied the following showed significant association with NTD in the offspring: diabetes mellitus; organic heart disease; lung disease; and diuretic, antihistamine, and sulfonamide use. The interval between the termination of the immediately previous pregnancy and the start of the proband pregnancy was significantly shorter in mothers of NTD children than in mothers of control infants. The risk for NTD was also significantly increased if the immediately previous pregnancy was a spontaneous abortion. There was no increased risk for NTDs among sibs of children with major malformations such as tracheo-esophageal "dysraphism," cleft lip/palate, or renal agenesis. NTDs are apparently etiologically heterogeneous.

Neural tube defects and sex ratios

The sex ratio of 147 fetuses with presumed multifactorial neural tube defect (NTD) was studied. Overall, the ratio (males:females) was 0.73 with expected female excess. However, when the NTDs were subdivided according to the site of the lesion, the sex ratios varied. Total craniorachischisis, anencephaly with cervical spina bifida, holoacrania, and thoracic spina bifida showed a greater female excess than that overall; the sex ratio for meroacrania was close to unity, while that for low spinal lesions, particularly those involving the sacrum, showed an extreme bias towards males. These findings are related to the mode of formation of the neural tube. Females seem prone to defects of neurulation and males to defects in canalization. An explanation for these findings is suggested in possible sex differences in rate of early embryonic development.

Neural tube defects: epidemiology, detection, and prevention

Neural tube defects are common congenital malformations of the central nervous system and include anencephaly, spina bifida, and encephalocele. Prenatal detection by amniotic fluid analysis of alpha-fetoprotein is possible in those women known to be at high risk for neural tube defects. Maternal serum screening for increased alpha-fetoprotein levels is now available nationally and has the potential to identify women who otherwise would not be known to be at risk. The epidemiology, detection, screening, and prevention of neural tube defects are discussed, and an explanation of alpha-fetoprotein and its use in screening is offered.

Prenatal diagnosis policy without routine amniocentesis in pregnancies with a positive family history for neural tube defects

The recurrence risk for neural tube defects in pregnancies of women with a family history of neural tube defects greatly exceeds the general population risk. In these high risk pregnancies, we used a prenatal diagnostic method differing from that usually employed, relying mainly on the results of maternal serum alpha-fetoprotein (MSAFP) and ultrasound examination, without routine amniocentesis. During the 6 years reviewed in this study, this method was applied in 539 pregnancies. Of a total of 20 neural tube defects, 19 were detected using this combination of MSAFP, ultrasound, and selective amniocentesis, and the authors estimate that about 8-10 spontaneous abortions were avoided because only 28 amniocenteses were carried out instead of 539. The risk of recurrence was found to be lower than that experienced earlier.

Risks to sibs of probands with neural tube defects: data for clinic populations in British Columbia

The purpose of this study is to determine whether couples receiving genetic counselling because of a child with a neural tube defect (NTD) are a selected group and therefore not representative of the general population with respect to sib risks for NTDs. British Columbia (B.C.) provides an excellent opportunity to look at this for several reasons. Firstly, genetic counselling services are centralized. Secondly, there is virtually complete ascertainment of all infants with NTDs in the province. Thirdly, sib risks for NTDs in the general population have been derived previously [McBride, 1979] and, therefore, are available for comparison with the risks for sibships in the clinic populations. In the present study, data were available on 398 sibships in which the index case had anencephaly and/or spina bifida. In all instances, sib risks for the clinic populations did not differ significantly from those for the general population. In addition, congenital malformations other than NTDs did not occur among sibs of index cases more often than expected, based on provincial incidence data.

Neural tube defects: a review of human and animal studies on the etiology of neural tube defects

Although neural tube defects are a common congenital anomaly, their etiology is not known. Human studies have emphasized the pathology and epidemiology of the defects and suggest that in the majority of cases the etiology is multifactorial. Factors which appear possibly to be important are genetic predisposition, maternal illness, and fetal drug exposure. Animal studies have utilized naturally occurring neural tube defects and teratologically induced lesions. No animal model has been convincingly established as the equivalent of human neural tube defects. However, animal models have allowed investigation of the mechanisms of suggested human teratogens and determination of the pathogenesis of naturally occurring animal defects. Their most important contribution has been in furthering the understanding of the normal mechanisms of neural tube closure. It may be through this understanding that the etiology of human neural tube defects will be determined.

Etiological study on isolated esophageal atresia

A study group of 160 index patients with isolated esophageal atresia, a control group of 160 matched healthy controls, and the first-degree relatives of patients and controls were examined; epidemiological, family planning, teratological, and genetic data were obtained by personal interview in the study and control groups. One half of the index patients were male. Intrauterine growth retardation, a higher proportion of mothers under 19 or over 30 years of age, and less skilled professions of the parents were found in the study group. There were more extramarital conceptions, more pregnancies in spite of the use of contraceptive pills, and more delayed conceptions in index patients' mothers. The teratogens studied did not have an obvious pathological effect here. The sib occurrence of isolated esophageal atresia was 0.43%, which did not correspond too well to the expected figure of 1.34% based on the polygenic model.

A family study of congenital diaphragmatic defects

The occurrence of specific and nonspecific congenital anomalies was determined in first degree relatives of index patients with congenital diaphragmatic defects who were born in Hungary between 1970 and 1979 and were ascertained through a population-based registry. The cases were grouped into Bochdalek types (N = 156), other types (N = 26), unclassified types (N = 55), and multiple congenital anomalies (MCA) cases including those with congenital diaphragmatic defects (N = 96). The sib occurrence in the Bochdalek type was 0.9% (taking into consideration also the unclassified cases or the total material, it was 0.5% or 0.4%, respectively). Specific familial clusters were not found in other types. Neural tube defects were detected in 1.8% of sibs in the total material and 2.4% in MCA cases.

Possible causal heterogeneity in spina bifida cystica

A study was performed to determine whether causal heterogeneity can be demonstrated among the nonsyndromal spina bifida cysticas based on the vertebral level of the defect. Two groups were compared, probands with defects at or above T 11, likely representing defects of neuralization, and probands with defects at or below T 12, likely defects of canalization. Differences between the two groups were found with respect to reproductive history and occurrence of other malformations. A high degree of concordance for the type of defect among affected sib pairs was also observed. These findings indicate that there is probably heterogeneity within the spina bifida cysticas based on the level of the defect.

X-linked midline defects

Opitz and Gilbert [Am J Med Genet 12:443-455, 1982] have postulated that the midline may be a kind of developmental field. Although developmental field defects (primary malformations) usually occur sporadically, in some instances they can be caused by a single gene mutation. We report on a family in which the occurrence of midline defects was consistent with X-linked inheritance. Anomalies present in the family include hydrocephalus, anencephaly, cleft lip, congenital heart defect, renal agenesis, and hypospadias.

The epidemiology of spina bifida in south-western Ohio--1970-1979

Multiple epidemiological variables of 131 children with spina bifida born during 1970 and 1979 in a seven-county urban/rural region of south-western Ohio were analyzed retrospectively via personal interviews, hospital and clinic records, and birth and stillbirth certificates. The estimated incidence of spina bifida was 0.69/1000. It did not vary over the 10 years, seasonally, or in the urban vs. rural areas. The incidence for whites was three times that for non-whites. Reporting of spina bifida on the birth certificate was found for 52 per cent. Fetal loss in the children's mothers was similar to that for controls. However, there was a high number of therapeutic abortions just prior to the conception of the child with spina bifida. Oral contraceptives were used in the early months of the affected pregnancy more frequently than in controls. Recurrence risk was 3.2 per cent. Almost 12 per cent of the children with spina bifida had other major malformations. Even when the deceased probands were discounted, the malformation rate was higher than in the general population. Siblings of affected children had a less impressive but still increased rate of malformations.

Maternal serum alpha-fetoprotein screening for neural tube defects. Report of a combined study in Germany and short overview on screening in populations with low birth prevalence of neural tube defects

The basis of maternal serum alpha-fetoprotein (AFP)-screening for neural tube defects is discussed. A report is given of a large scale screening study in the Federal Republic of Germany combining the experiences in Giessen and Hannover on over 50,000 pregnant women, about evenly distributed among both centers. Published and known forthcoming data from other low incidence populations, particularly of European countries, are reviewed briefly. The conclusion is reached that general screening could effectively be instituted and in the final result should also be cost-beneficial.

Recurrence risk after neural tube defects in a genetic counselling clinic

The recurrence of isolated neural tube defects in a population of women from a genetic counselling clinic was found to be 3.4%. After one baby with a neural tube defect the recurrence was 2.3%. Of the 15 pregnancies of women who had two previous babies with neural tube defects, there were three further recurrences. These findings show that the Hungarian recurrence risk of isolated neural tube defects has not changed with a declining birth prevalence, and that the rate in genetic counselling clinic patients is the same as in a previous population based epidemiological study.

Additional data on spontaneous abortion and facial cleft malformations

Examination of fetal wastage data for a large collection of CL +/- P and CP sibships reported previously (Bear 1978) does not indicate the frequency of recognized abortion to be higher in the sibships of CL + P vs CL index cases, female vs male CL +/- P index cases, bilateral vs unilateral CL +/- P index cases, female bilateral CL +/- P index cases vs male unilateral CL +/- P index cases, or male vs female CP index cases. These observations fail to confirm those reported by Dronamraju (Dronamraju et al. 1982, Dronamraju & Bixler 1983a, b), and provide no evidence of a positive relation between degree of liability to facial cleft malformation and fetal mortality.

Congenital malformations associated with anencephaly in the Fylde peninsula of Lancashire

The necropsy reports of 174 cases of anencephaly, born in the Fylde peninsula of Lancashire between 1957 and 1980, have been analysed for the presence of other malformations. The results were compared with a similar previous series from Bristol, though the Bristol study differed both in time (1948 to 1975) and in the fact that it was hospital based and, unlike the present study, did not achieve near complete ascertainment. Of the Lancashire anencephalics, 24% had other malformations, a significantly lower rate than in the Bristol series. There was a much higher rate of renal and urinary tract defects in the Bristol series, and a higher rate of cardiovascular defects in the Lancashire series. The distribution of associated malformations differed in the two areas, possibly representing different patterns of aetiological heterogeneity. The iniencephaly rate was so much lower in Lancashire as to suggest an artefact, perhaps owing to the lack of a precise definition of the condition.

Empirical recurrence risk after unidentified multiple congenital abnormalities

Thirty-five fetal deaths (30.4%) and 12 cases of congenital abnormality (15.0%) occurred in 117 subsequent pregnancies and 80 sibs of 112 consultands who had babies with unidentified multiple congenital abnormalities after genetic counselling. The specific recurrence risk of unidentified multiple congenital abnormalities was 5%.

Neural tube defects in the Sikhs

Background information on the incidence of neural tube defects (NTD) in Sikhs in India and elsewhere is given. The incidence of NTD in the Sikh population of British Columbia is estimated for 4 years and found to be 2.86 per 1,000 births. The overall rate for NTD in all B.C. births for these same years is 1.26 per 1,000 births. This difference is statistically significant. Analysis of cases showed that a greater proportion of Sikh cases are stillborn, and these account for much of the excess over expected. It appears that the incidence of NTD in Sikhs is increased compared to the general population incidence of these birth defects in B.C.

Occurrence of neural tube defects among first-, second-, and third-degree relatives of probands: results of a United States study

Data on the occurrence of neural tube defects in first-, second-, and third-degree relatives of probands were collected in a United States study. The proportions of affected individuals were 3.2%, 0.5%, and 0.17% respectively. These findings are compared to those from other recent North American studies, and differences are discussed. It is pointed out that accurate recurrence risk figures may not be available, and that caution should be used when counseling families with relatives who are affected with NTD.