Linking a European cohort of children born with congenital anomalies to vital statistics and mortality records: A EUROlinkCAT study

EUROCAT is a European network of population-based congenital anomaly (CA) registries. Twenty-one registries agreed to participate in the EUROlinkCAT study to determine if reliable information on the survival of children born with a major CA between 1995 and 2014 can be obtained through linkage to national vital statistics or mortality records. Live birth children with a CA could be linked using personal identifiers to either their national vital statistics (including birth records, death records, hospital records) or to mortality records only, depending on the data available within each region. In total, 18 of 21 registries with data on 192,862 children born with congenital anomalies participated in the study. One registry was unable to get ethical approval to participate and linkage was not possible for two registries due to local reasons. Eleven registries linked to vital statistics and seven registries linked to mortality records only; one of the latter only had identification numbers for 78% of cases, hence it was excluded from further analysis. For registries linking to vital statistics: six linked over 95% of their cases for all years and five were unable to link at least 85% of all live born CA children in the earlier years of the study. No estimate of linkage success could be calculated for registries linking to mortality records. Irrespective of linkage method, deaths that occurred during the first week of life were over three times less likely to be linked compared to deaths occurring after the first week of life. Linkage to vital statistics can provide accurate estimates of survival of children with CAs in some European countries. Bias arises when linkage is not successful, as early neonatal deaths were less likely to be linked. Linkage to mortality records only cannot be recommended, as linkage quality, and hence bias, cannot be assessed.

Prevention of neural tube defects in the UK: a missed opportunity

OBJECTIVE

In 1991, the Medical Research Council (MRC) Vitamin Study demonstrated that folic acid taken before pregnancy and in early pregnancy reduced the risk of a neural tube defect (NTD). We aimed to estimate the number of NTD pregnancies that would have been prevented if flour had been fortified with folic acid in the UK from 1998 as it had been in the USA.

DESIGN

Estimates of NTD prevalence, the preventive effect of folic acid and the proportion of women taking folic acid supplements before pregnancy were used to predict the number of NTD pregnancies that would have been prevented if folic acid fortification had been implemented.

SETTING

Eight congenital anomaly registers in England and Wales.

MAIN OUTCOME MEASURES

The prevalence of pregnancies with an NTD in the UK and the number of these pregnancies that would have been prevented if folic acid fortification had been implemented.

RESULTS

From 1991 to 2012, the prevalence of NTD pregnancies was 1.28 (95% CI 1.24 to 1.31) per 1000 total births (19% live births, 81% terminations and 0.5% stillbirths and fetal deaths ≥20 weeks' gestation). If the USA levels of folic acid fortification from 1998 onwards had been adopted in the UK, an estimated 2014 fewer NTD pregnancies would have occurred.

CONCLUSIONS

Failure to implement folic acid fortification in the UK has caused, and continues to cause, avoidable terminations of pregnancy, stillbirths, neonatal deaths and permanent serious disability in surviving children.

Large-scale discovery of novel genetic causes of developmental disorders

Despite three decades of successful, predominantly phenotype-driven discovery of the genetic causes of monogenic disorders, up to half of children with severe developmental disorders of probable genetic origin remain without a genetic diagnosis. Particularly challenging are those disorders rare enough to have eluded recognition as a discrete clinical entity, those with highly variable clinical manifestations, and those that are difficult to distinguish from other, very similar, disorders. Here we demonstrate the power of using an unbiased genotype-driven approach to identify subsets of patients with similar disorders. By studying 1,133 children with severe, undiagnosed developmental disorders, and their parents, using a combination of exome sequencing and array-based detection of chromosomal rearrangements, we discovered 12 novel genes associated with developmental disorders. These newly implicated genes increase by 10% (from 28% to 31%) the proportion of children that could be diagnosed. Clustering of missense mutations in six of these newly implicated genes suggests that normal development is being perturbed by an activating or dominant-negative mechanism. Our findings demonstrate the value of adopting a comprehensive strategy, both genome-wide and nationwide, to elucidate the underlying causes of rare genetic disorders.

Trends in the prevalence, risk and pregnancy outcome of multiple births with congenital anomaly: a registry-based study in 14 European countries 1984-2007

OBJECTIVE

To assess the public health consequences of the rise in multiple births with respect to congenital anomalies.

DESIGN

Descriptive epidemiological analysis of data from population-based congenital anomaly registries.

SETTING

Fourteen European countries.

POPULATION

A total of 5.4 million births 1984-2007, of which 3% were multiple births.

METHODS

Cases of congenital anomaly included live births, fetal deaths from 20 weeks of gestation and terminations of pregnancy for fetal anomaly.

MAIN OUTCOME MEASURES

Prevalence rates per 10,000 births and relative risk of congenital anomaly in multiple versus singleton births (1984-2007); proportion prenatally diagnosed, proportion by pregnancy outcome (2000-07). Proportion of pairs where both co-twins were cases.

RESULTS

Prevalence of congenital anomalies from multiple births increased from 5.9 (1984-87) to 10.7 per 10,000 births (2004-07). Relative risk of nonchromosomal anomaly in multiple births was 1.35 (95% CI 1.31-1.39), increasing over time, and of chromosomal anomalies was 0.72 (95% CI 0.65-0.80), decreasing over time. In 11.4% of affected twin pairs both babies had congenital anomalies (2000-07). The prenatal diagnosis rate was similar for multiple and singleton pregnancies. Cases from multiple pregnancies were less likely to be terminations of pregnancy for fetal anomaly, odds ratio 0.41 (95% CI 0.35-0.48) and more likely to be stillbirths and neonatal deaths.

CONCLUSIONS

The increase in babies who are both from a multiple pregnancy and affected by a congenital anomaly has implications for prenatal and postnatal service provision. The contribution of assisted reproductive technologies to the increase in risk needs further research. The deficit of chromosomal anomalies among multiple births has relevance for prenatal risk counselling.

The evolution of prenatal screening and diagnosis and its impact on an unselected population over an 18-year period

OBJECTIVE

To review changes in and impact of prenatal screening and diagnosis.

DESIGN

Population-based congenital anomaly register study.

SETTING

Oxfordshire.

POPULATION

Congenital anomalies confirmed and those suspected prenatally, delivered 1991-2008.

METHODS

Analysis of proportions of congenital anomalies confirmed and those suspected prenatally.

MAIN OUTCOME MEASURES

Birth prevalence, prenatal detection rates, pregnancy outcomes.

RESULTS

A total of 2651 (2.3%) infants/fetuses had a congenital anomaly diagnosed. There were 3839 suspected or confirmed cases, 2847 due to a prenatal suspicion, of which 1659 had an anomaly confirmed at delivery, and 1188 false-positive diagnoses, 91% due to reporting ultrasound normal variants. The percentage of prenatal notifications rose from 48% in 1991-93 to 83-88% from 1996 to 2003 and dropped to 61% in 2006-08, partly reflecting changes in the reporting of normal variants. Reporting these increased the prenatal diagnosis rate from 53 to 63% with an increase in false-positive rate from 0.09 to 1.04%. A total of 722 (44% of prenatally detected affected fetuses) resulted in termination; 48% of these had chromosome anomalies, 34% had isolated structural anomalies, 7% had multiple anomalies, 10% had familial disorders; 42% had lethal anomalies and 58% would probably have survived the neonatal period giving an estimated 20% reduction in birth prevalence of congenital anomalies compatible with survival because of terminations.

CONCLUSION

There has been an improvement in prenatal detection of congenital anomalies over the two decades studied. The recognition that reporting normal variants, although increasing prenatal detection rates, leads to an increase in false-positive diagnoses has had an impact on practice that has redressed the balance between these two effects.

The hidden mortality of transposition of the great arteries and survival advantage provided by prenatal diagnosis

OBJECTIVE

To describe the sensitivity of fetal anomaly scanning at detecting transposition of the great arteries (TGA) and to investigate whether prenatal detection improves survival.

DESIGN

Retrospective review of survival by comparing those who had an antenatal diagnosis with those who did not.

SETTING

Population-based study in Wessex region over 13 years.

POPULATION

Babies with isolated TGA and an intact ventricular septum.

METHODS

Review of outcomes by comparing those who had an antenatal diagnosis with those who did not.

MAIN OUTCOME MEASURES

Mortality rates in each group.

RESULTS

TGA occurred more commonly in boys than in girls. Using the existing national screening policy, the antenatal detection rate of TGA was only 6.9% over the study period, improving to 25% in the last 4 years. This contrasts with a 40% detection rate when TGA was associated with a ventricular septal defect (VSD). All the babies who had TGA diagnosed antenatally survived through surgery. Of those who were not diagnosed antenatally, two were stillborn, five died before the diagnosis was made and four died after surgery. Although the difference in survival rates between those who were antenatally diagnosed and those who were not is not statistically significant (chi(2)= 3.9; P = 0.11), some of these deaths could have been prevented if a prenatal diagnosis had been made.

CONCLUSIONS

Improved antenatal diagnosis could lead to a significant reduction in the mortality associated with TGA. The current low detection rate of TGA in the UK could be improved by the inclusion of outflow tract views in routine fetal anomaly scans, and we believe that the extra workload is justified.

An aetiological classification of birth defects for epidemiological research

BACKGROUND

Congenital anomaly registers collect data on antenatally and postnatally detected anomalies for surveillance, research, and public health purposes. Each anomaly is coded using the International Statistical Classification of Diseases and Related Health Problems (ICD-9/ICD-10) based on body systems, allowing accurate comparisons between registers for individual anomalies. When commencing an environmental, epidemiological study, it became clear to us that there is no standard classification that takes aetiology into account. This paper describes a new classification for use in studies addressing aetiology.

METHOD

A classification system was evolved and piloted using cases in a study of geographical variation in congenital anomaly prevalence.1 Cases that were difficult to categorise were noted, and after discussion with a team of experts, the classification was adjusted accordingly.

RESULTS AND CONCLUSION

A robust, hierarchical method of classifying birth defects into eight categories has been produced, for use at source of data registration in conjunction with, but independent of, ICD coding.

Prevalence of congenital anomalies in five British regions, 1991-99

AIMS

To describe trends in total and live birth prevalence, regional differences in prevalence, and outcome of pregnancy of selected congenital anomalies.

METHODS

Population based registry study of 839,521 births to mothers resident in five geographical areas of Britain during 1991-99. Main outcome measures were: total and live birth prevalence; pregnancy outcome; proportion of stillbirths due to congenital anomalies; and secular trends.

RESULTS

The sample consisted of 10,844 congenital anomalies, giving a total prevalence of 129 per 10,000 registered births (95% CI 127 to 132). Live birth prevalence was 82.2 per 10,000 births (95% CI 80.3 to 84.2) and declined significantly with time. The proportion of all stillbirths with a congenital anomaly was 10.5% (453 stillbirths). The proportion of pregnancies resulting in a termination increased from 27% (289 cases) in 1991 to 34.7% (384 cases) in 1999, whereas the proportion of live births declined from 68.2% (730 cases) to 58.5% (648 cases). Although similar rates of congenital anomaly groups were notified to the registers, variation in rates by register was present. There was a secular decline in the total prevalence of non-chromosomal and an increase in chromosomal anomalies.

CONCLUSIONS

Regional variation exists in the prevalence of specific congenital anomalies. For some anomalies this can be partially explained by ascertainment variation. For others (neural tube defects, diaphragmatic hernia, gastroschisis), higher prevalence rates in the northern regions (Glasgow and Northern) were true differences. Live birth prevalence declined over the study due to an increase in terminations of pregnancy.

Congenital anomaly surveillance in England--ascertainment deficiencies in the national system

OBJECTIVE

Firstly, to assess the completeness of ascertainment in the National Congenital Anomaly System (NCAS), the basis for congenital anomaly surveillance in England and Wales, and its variation by defect, geographical area, and socioeconomic deprivation. Secondly, to assess the impact of the lack of data on pregnancies terminated because of fetal anomaly.

DESIGN

Comparison of the NCAS with four local congenital anomaly registers in England.

SETTING

Four regions in England covering some 109,000 annual births.

PARTICIPANTS

Cases of congenital anomalies registered in the NCAS (live births and stillbirths) and independently registered in the four local registers (live births, stillbirths, fetal losses from 20 weeks' gestation, and pregnancies terminated after prenatal diagnosis of fetal anomaly).

MAIN OUTCOME MEASURE

The ratio of cases identified by the national register to those in local registry files, calculated for different specified anomalies, for whole registry areas, and for hospital catchment areas within registry boundaries.

RESULTS

Ascertainment by the NCAS (compared with data from local registers, from which terminations of pregnancy were removed) was 40% (34% for chromosomal anomalies and 42% for non-chromosomal anomalies) and varied markedly by defect, by local register, and by hospital catchment area, but not by area deprivation. When terminations of pregnancy were included in the register data, ascertainment by NCAS was 27% (19% for chromosomal anomalies and 31% for non-chromosomal anomalies), and the geographical variation was of a similar magnitude.

CONCLUSION

The surveillance of congenital anomalies in England is currently inadequate because ascertainment to the national register is low and non-uniform and because no data exist on termination of pregnancy resulting from prenatal diagnosis of fetal anomaly.

Contribution of ultrasonographic examination to the prenatal detection of trisomy 21: experience from 19 European registers

The objective of this study was to evaluate the contribution of ultrasound scanning to the prenatal detection of trisomy 21 in a large unselected European population. Data from 19 congenital malformation registers in 11 European countries were included. The prenatal ultrasound screening programs in the countries ranged from no routine screening to three ultrasound investigations per patient. Routine serum screening was offered in four of the 11 countries and routine screening on the basis of maternal age amniocentesis in all. The results show that overall 53% of cases of trisomy 21 were detected prenatally with a range from 3% in Lithuania to 88% in Paris. Ninety-eight percent of women whose babies were diagnosed before 24 weeks gestation chose to terminate the pregnancy. Centres/countries that offer serum screening do not have a significantly higher detection rate of trisomy 21 when compared to those that offer maternal age amniocentesis and anomaly scanning only. Fifty percent of trisomy 21 cases were born to women aged 35 years or more. In conclusions, second trimester ultrasound plays an important role in the prenatal diagnosis of trisomy 21. Of those cases prenatally diagnosed, 64% of cases in women <35 years and 36% of those in women >or=35 years were detected because of an ultrasound finding. Ultrasound soft markers accounted for 84% of the scan diagnoses. There is evidence of increasing maternal age across Europe with 50% of cases of trisomy 21 born to women aged 35 years or more.

Unusual prenatal presentation of Beckwith–Wiedemann syndrome

When Beckwith-Wiedemann syndrome (BWS) is detected prenatally, it is usually on the basis of macroglossia, exomphalos or enlarged kidneys. We describe a case that presented as gross hepatomegaly and a suspected enlarged pancreas at 20 weeks' gestation, with none of the usual features.

Fetal renal anomalies and genetic syndromes

Renal abnormalities are some of the commonest and most easily detectable anomalies on ultrasound. Many are an isolated finding but the prognosis may be altered considerably by the detection of other anomalies which could indicate a genetic disorder or syndrome. It is often easier to detect presupposed anomalies and the purpose of this article is to introduce and discuss those syndromes that may present with a renal abnormality on ultrasound. Common renal findings are presented with the range of additional anomalies that should be sought and suggested diagnostic tests. It should be remembered that although for many genetic conditions specific mutation analysis is now available, this usually requires pre-pregnancy investigations. Furthermore, in some cases the definitive diagnosis may not be suspected until post mortem. By this time it may be too late to establish a cell line to confirm the suspicion using laboratory methods. It is therefore important to take tissue samples antenatally where possible, or at delivery, as postnatal samples may have a high culture failure rate.

Six year survey of screening for Down's syndrome by maternal age and mid-trimester ultrasound scans

OBJECTIVE

To assess the effectiveness of antenatal screening for Down's syndrome by maternal age and routine mid-pregnancy ultrasound scanning.

DESIGN

Retrospective six year survey.

SETTING

Maternity units of a district general hospital.

SUBJECTS

Pregnant women booked for delivery in hospital between 1 January 1993 and 31 December 1998.

MAIN OUTCOME MEASURES

All cases of Down's syndrome occurring in district identified from regional congenital anomaly register and cytogenetic laboratory records. Women's case notes were examined to identify indication for karyotyping, gestation at diagnosis, and outcome of pregnancy.

RESULTS

31 259 deliveries occurred during study period, and 57 cases of Down's syndrome were identified, four in failed pregnancies and 53 in ongoing pregnancies or in neonates. The analysis was confined to ongoing pregnancies or liveborn children. Invasive antenatal tests were performed in 6.6% (2053/31 259), and 68% (95% confidence interval 56% to 80%) of cases of Down's syndrome were detected antenatally, giving a positive predictive value of 1.8%. There were 17 undetected cases, and in seven of these the women had declined an offer of invasive testing. In women aged less than 35 years the detection rate was 53% (30% to 76%). Most of the cases detected in younger women followed identification of ultrasound anomalies.

CONCLUSIONS

The overall detection rate was considerably higher than assumed in demonstration projects for serum screening. As a result, the benefits of serum screening are much less than supposed. Before any new methods to identify Down's syndrome are introduced, such as nuchal translucency or first trimester serum screening, the techniques should be tested in properly controlled trials.

Asymmetry and skin pigmentary anomalies in chromosome mosaicism

We report six persons mosaic for a chromosome anomaly. All were mentally retarded and dysmorphic. Unilateral or asymmetrical features were found in all cases, in one an unusual transverse terminal limb anomaly, and in the others various degrees of hemiatrophy of the left side of the body. Five of the subjects had skin pigmentary anomalies which were distributed in the lines of Blaschko. The abnormal cell lines found were ring chromosome 22, trisomy 22, a large acrocentric marker, a deletion of 18q, a deletion of 8q, and triploidy. In four cases the clinical diagnosis was only confirmed by skin biopsy. In one case low level mosaicism in blood was fortuitously detected because of cytogenetic fragile X screening and confirmed in a skin biopsy. The sixth case was of dynamic mosaicism of a non-mosaic deletion 18q with a chromosome 18 derived marker present in a proportion of cells. Chromosome mosaicisn may cause subtle and asymmetrical clinical features and can require repeated cytogenetic investigations. The diagnosis should be actively sought as it enables accurate genetic counselling to be given.

A new form of X-linked, high-frequency, sensorineural deafness

A kindred is described in which five male members over three generations manifested a high-frequency deafness. Their isolated sensorineural hearing loss was non-progressive and only in the 1500-8000 Hz range. The pattern of inheritance and nature of the auditory deficit would suggest it is a previously undescribed X-linked form of deafness.

The aetiology of intellectual disability in Western Australia: a community-based study

A register of intellectual disability is being established to assess the level and aetiology of intellectual disability in all children born and/or living in Western Australia. 1602 children aged between six and 16 years were identified who had IQs less than 70. 40 per cent had a definite genetic basis, 20 per cent an environmental cause and 40 per cent were of unknown aetiology. The insult was prenatal in 61 per cent, 10 per cent had a possible perinatal cause, 8 per cent were postnatal and for 21 per cent the timing could not be assessed. Approximately 20 per cent had concomitant cerebral palsy and 13 per cent were epileptic. A disparity was found between rural and urban areas, the prevalence being 9.9 and 6.5 per 1000 live births.

Cataracts, aberrant oral frenula, and growth retardation: a new autosomal dominant syndrome

We report on a mother and her two children with an autosomal dominant cataract syndrome with associated aberrant oral frenula, growth retardation, and specific facial appearance. Their phenotype differs from that of other reported cataract syndromes, and we conclude that this is a previously undescribed entity.

Assignment of the locus for Waardenburg syndrome type I to human chromosome 2q37 and possible homology to the Splotch mouse

We have demonstrated close linkage between the locus for the autosomal dominant Waardenburg syndrome type I and the placental alkaline phosphatase locus on chromosome 2q37. In five families the peak lod score was 4.76 at a recombination fraction of .023. In the mouse the Splotch locus maps to near the homologous position. Splotch mice have white spotting and hearing defects, suggesting that Splotch may be the murine homologue of Waardenburg syndrome type I.

Simultaneous trisomy 9q3 and monosomy 5p in two children with der(5),t(5;9)(p15.1;q34.13): report of an extended family

We present a family segregating for t(5;9)(p15.1;q34.13). Two cases with der(5),t(5;9), resulting in a partial duplication 9q34.13----qter and partial deletion of 5p15.12----pter, were ascertained. The phenotypes were consistent with features of both the cri du chat and trisomy 9q3 syndromes.