Detection and investigation of temporal clusters of congenital anomaly in Europe: seven years of experience of the EUROCAT surveillance system

A multidisciplinary and structured investigation of three suspected clusters of transverse upper limb reduction defects in France

INTRODUCTION

Between 2019-2021, facing public concern, a scientific expert committee (SEC) reanalysed suspected clusters of transverse upper limb reduction defects (TULRD) in three administrative areas in France, where initial investigations had not identified any risk exposure. We share here the national approach we developed for managing suspicious clusters of the same group of congenital anomalies occurring in several areas.

METHODS

The SEC analysed the medical records of TURLD suspected cases and performed spatiotemporal analyses on confirmed cases. If the cluster was statistically significant and included at least three cases, the SEC reviewed exposures obtained from questionnaires, environmental databases, and a survey among farmers living near to cases' homes concerning their plant product use.

RESULTS

After case re-ascertainment, no statistically significant cluster was observed in the first administrative areas. In the second area, a cluster of four children born in two nearby towns over two years was confirmed, but as with the initial investigations, no exposure to a known risk factor explaining the number of cases in excess was identified. In the third area, a cluster including just two cases born the same year in the same town was confirmed.

DISCUSSION

Our experience highlights that in the event of suspicious clusters occurring in different areas of a country, a coordinated and standardised approach should be preferred.

Teratogenicity and Reactive Oxygen Species after transient embryonic hypoxia: Experimental and clinical evidence with focus on drugs causing failed abortion in humans

Teratogenicity and Reactive Oxygen Species after transient embryonic hypoxia: Experimental and clinical evidence with focus on drugs with human abortive potential. Reactive Oxygen Species (ROS) can be harmful to embryonic tissues. The adverse embryonic effects are dependent on the severity and duration of the hypoxic event and when during organongenesis hypoxia occurs. The vascular endothelium of recently formed arteries in the embryo is highly susceptible to ROS damage. Endothelial damage results in vascular disruption, hemorrhage and maldevelopment of organs, which normally should have been supplied by the artery. ROS can also induce irregular heart rhythm in the embryo resulting in alterations in blood flow and pressure from when the tubular heart starts beating. Such alterations in blood flow and pressure during cardiogenesis can result in a variety of cardiovascular defects, for example transpositions and ventricular septal defects. One aim of this article is to review and compare the pattern of malformations produced by transient embryonic hypoxia of various origins in animal studies with malformations associated with transient embryonic hypoxia in human pregnancy due to a failed abortion process. The results show that transient hypoxia and compounds with potential to cause failed abortion in humans, such as misoprostol and hormone pregnancy tests (HPTs) like Primodos, have been associated with a similar spectrum of teratogenicity. The spectrum includes limb reduction-, cardiovascular- and central nervous system defects. The hypoxia-ROS related teratogenicity of misoprostol and HPTs, is likely to be secondary to uterine contractions and compression of uterinoplacental/embryonic vessels during organogenesis.

The trend of marriage, childbearing, and divorce and its determinants of socio-economic factors on divorce in Yazd province 2016-2021: A cross-sectional study

Background

In recent decades, families and their stability as an important social institution have changed significantly.

Objective

This study aimed to investigate the marriage trends, childbearing, and divorce changes in Yazd province from 2016 to 2021 to estimate the effect of socioeconomic factors on divorce.

Materials and Methods

A cross-sectional study was done in 2 phases. In the first phase, an ecological (time trend) was conducted to investigate the 5 yr trend in the occurrence of marriage, childbearing, and divorce, as well as the factors affecting the occurrence of divorce in the second phase. For the second phase of the study, 600 participants were selected. 300 divorced and 300 married applicants were chosen between 2016 and 2021. A binary logistic regression model was used to find the related factors affecting the occurrence of divorce.

Results

The results showed a declining marriage (p = 0.05) and childbearing trend (p = 0.84), as well as an increasing trend in divorces (p = 0.02) in Yazd. Logistic regression analysis showed that college education (OR = 0.22, CI: 0.116-0.430, p < 0.001) and being self-employed (OR = 0.48, CI: 0.255-0.934, p = 0.03) could reduce the odds of divorce. In addition, nonresidents (OR = 2.1, CI: 1.314-3.562, p < 0.001), with > 10-yr age differences (OR = 3.8, CI: 1.803-8.213, p < 0.001) or the woman being older than her husband (OR = 3.4, CI: 1.981-5.848, p < 0.001) could increase the odds of divorce.

Conclusion

Our results confirmed that a combination of socioeconomic characteristics affects the stability of family institutions.

Student A, Pourkashani P, Tabatabaei Z, Eftekhar E, Saberi M, Mahjoubi F. Prenatal diagnosis of Sex determining region Y -box transcription factor 2 anophthalmia syndrome caused by germline mosaicism using next-generation sequencing: A case report

Background

Sex determining region Y box transcription factor 2 (SOX2) mutations lead to bilateral anophthalmia with autosomal dominant human inheritance. SOX2 mutations could result in severe ocular phenotypes usually associated with variable systemic defects. Most patients described with SOX2 anophthalmia syndrome possessed de novo mutations in this gene.

Case Presentation

In this case report, we describe 2 brothers with mental retardation and bilateral anophthalmia caused due to SOX2 germline mosaicism in unaffected parents. Next-generation DNA sequencing was carried out to determine the family's possible cause of genetic mutation. Sanger sequencing was performed on the patients and their parents. Prenatal diagnosis was done in both pregnancies of the older brother's wife via chorionic villus sampling. A novel heterozygous pathogenic frameshift deletion variant (exon1:c.58_80del:p.G20fs) was identified in the SOX2 gene, which was confirmed by Sanger sequencing in both affected brothers and did not exist in healthy parents, indicating germline mosaicism.

Conclusion

Most SOX2 mutations known look to arise de novo in probands and are diagnosed through anophthalmia or microphthalmia. Prenatal diagnosis should be offered to healthy parents with a child with SOX2 mutation every pregnancy.

Prevalence of congenital anomalies and related factors in live births in Zahedan, Southeast of Iran: A cross-sectional study

Background

The term congenital anomalies (CAs) refers to structural or functional abnormalities at the time of conception. Approximately 12 deaths related to congenital disabilities occur in every 10,000 babies born.

Objective

This study aimed to evaluate the prevalence and associated factors of single and multiple CAs in live births in Zahedan, Southeast Iran.

Materials and Methods

This cross-sectional study was conducted on 59,087 live births in a referral hospital in Zahedan located in the southeast of Iran from 2009 to 2019. All live births were examined by pediatricians and the CAs and categorized based on the international classification of diseases.

Results

Of 59,085 live births, at least 883 had a significant anomaly, and the prevalence rate of CAs was about 149 per 10,000. Anomalies of the nervous (24.1%) and cardiovascular systems (21.10%) were the most frequent, occurring in 213 and 187 of the live births, respectively. Spina bifida is the most common anomaly of the central nervous system. The most common anomalies in the cardiovascular system were unspecified heart malformations (17.1%), cardiovascular malformations (18.7%), and patent ductus arteriosus (11.7%). Significant correlations were found between the parent's consanguinity marriage, the mother's age, an existing anomaly in the family, and relatives in single and multiple CAs (p = 0.02, p = 0.02, p < 0.001, p = 0.01, respectively).

Conclusion

The prevalence of CAs was 149 per 10,000 live births. The highest prevalence of CAs was related to the central nervous system. Increasing the public's knowledge about fetal defects can reduce the prevalence of CAs.

EUROlinkCAT protocol for a European population-based data linkage study investigating the survival, morbidity and education of children with congenital anomalies

INTRODUCTION

Congenital anomalies (CAs) are a major cause of infant mortality, childhood morbidity and long-term disability. Over 130 000 children born in Europe every year will have a CA. This paper describes the EUROlinkCAT study, which is investigating the health and educational outcomes of children with CAs for the first 10 years of their lives.

METHODS AND ANALYSIS

EUROCAT is a European network of population-based registries for the epidemiological surveillance of CAs. EUROlinkCAT is using the EUROCAT infrastructure to support 22 EUROCAT registries in 14 countries to link their data on births with CAs to mortality, hospital discharge, prescription and educational databases. Once linked, each registry transforms their case data into a common data model (CDM) format and they are then supplied with common STATA syntax scripts to analyse their data. The resulting aggregate tables and analysis results are submitted to a central results repository (CRR) and meta-analyses are performed to summarise the results across all registries. The CRR currently contains data on 155 594 children with a CA followed up to age 10 from a population of 6 million births from 1995 to 2014.

ETHICS

The CA registries have the required ethics permissions for routine surveillance and transmission of anonymised data to the EUROCAT central database. Each registry is responsible for applying for and obtaining additional ethics and other permissions required for their participation in EUROlinkCAT.

DISSEMINATION

The CDM and associated documentation, including linkage and standardisation procedures, will be available post-EUROlinkCAT thus facilitating future local, national and European-level analyses to improve healthcare. Recommendations to improve the accuracy of routinely collected data will be made.Findings will provide evidence to inform parents, health professionals, public health authorities and national treatment guidelines to optimise diagnosis, prevention and treatment for these children with a view to reducing health inequalities in Europe.

Evidence for a cluster of rare birth defects in the Ain department (France)

BACKGROUND

REMERA (REgistre des Malformations En Rhône-Alpes) is a registry of congenital malformations that covers 58,000 births annually in Central-East France. In 2010, the registry raised an alarm to the health authorities (Santé publique France, SpF) about three cases of a unilateral isolated transverse upper limb reduction defect (UITULRD) in a small subarea; the general prevalence of this defect is one case in 10,000 births. In the following years, more infants were born with the same malformation in the same territory of the Ain department. Public health authorities, supported by an expert committee, rejected the existence of a cluster, but we aim here at providing evidence for this cluster.

METHODS

Geocoded data for all UITULRD cases (ICD-10 codes Q71.2 and Q71.3) were extracted from the REMERA database. We conducted a Kulldorff cluster analysis of these data, using the spatial SaTScanTM algorithm.

RESULTS

The analysis found a cluster of eight cases of UITULRD among the 8,204 births occurring between 2009 and 2014 within a circle of 16.24 km radius centered on a village of the Ain department, whereas 0.82 cases were expected under a uniform probability of such a birth throughout the registry territory. This represents an almost 10fold excess over the expected number of cases (p = .0057).

CONCLUSIONS

The arguments used to deny the cluster are disputed and we present the evidence supporting its reality. The controversy that has followed the alarm has compromised the search for the cause(s) of this excess of rare malformations.

Why Does Child Mortality Decrease With Age? Modeling the Age-Associated Decrease in Mortality Rate Using WHO Metadata From 14 European Countries

Background: Mortality rate rapidly decreases with age after birth, and, simultaneously, the spectrum of death causes show remarkable changes with age. This study analyzed age-associated decreases in mortality rate from diseases of all main chapters of the 10th revision of the International Classification of Diseases. Methods: The number of deaths was extracted from the mortality database of the World Health Organization. As zero cases could be ascertained for a specific age category, the Halley method was used to calculate the mortality rates in all possible calendar years and in all countries combined. Results: All causes mortality from the 1st day of life to the age of 10 years can be represented by an inverse proportion model with a single parameter. High coefficients of determination were observed for total mortality in all populations (arithmetic mean = 0.9942 and standard deviation = 0.0039). Slower or no mortality decrease with age was detected in the 1st year of life, while the inverse proportion method was valid for the age range [1, 10) years in most of all main chapters with three exceptions. The decrease was faster for the chapter "Certain conditions originating in the perinatal period" (XVI).The inverse proportion was valid already from the 1st day for the chapter "Congenital malformations, deformations and chromosomal abnormalities" (XVII).The shape of the mortality decrease was very different for the chapter "Neoplasms" (II) and the rates of mortality from neoplasms were age-independent in the age range [1, 10) years in all populations. Conclusion: The theory of congenital individual risks of death is presented and can explain the results. If it is valid, latent congenital impairments may be present among all cases of death that are not related to congenital impairments. All results are based on published data, and the data are presented as a supplement.

Down syndrome among primiparae at older maternal age: A test of the relaxed filter hypothesis

BACKGROUND

Down syndrome (DS) ranks as one of the most common birth defects in the United States. The relaxed filter hypothesis (RFH) asserts that mothers with no previous children but nearing reproductive senescence reduce fetal selectivity against DS pregnancies in the first trimester given the high probability of having no offspring at all if the DS pregnancy is not carried to term. We test the parity prediction of RFH-specifically, that pregnancies to older mothers with no previous live births show an elevated prevalence of DS above values expected from the separate contributions of older maternal age and primiparity.

METHODS

We retrieved maternal age and parity information on 2,748 DS cases (live, stillborn, or terminated due to anomaly) from the Paris Birth Defects Registry, 1983-2015. We used two waves of the Enquête Fertility Survey (n = 5,460) and counts of stillbirths to calculate total prevalence of DS by maternal age and parity.

RESULTS

Primiparous mothers 35+ years show the greatest prevalence of any parity group (9.78 cases per 1,000 deliveries). Tests for additive interaction of primiparity and older maternal age reject the null (relative excess risk due to interaction = 1.01; 95% confidence interval: 0.33, 1.69; null value on additive scale is 0).

CONCLUSIONS

Relaxed selection may account for 10% of the increase in the prevalence, among older primiparous mothers, of DS detected during or after the 11th week. Future work may hold implications for understanding, among older mothers, the strength of this maternal screen against other defects.

Chemically induced aneuploidy in germ cells. Part II of the report of the 2017 IWGT workgroup on assessing the risk of aneugens for carcinogenesis and hereditary diseases

As part of the 7th International Workshops on Genotoxicity Testing held in Tokyo, Japan in November 2017, a workgroup of experts reviewed and assessed the risk of aneugens for human health. The present manuscript is one of three manuscripts from the workgroup and reports on the unanimous consensus reached on the evidence for aneugens affecting germ cells, their mechanisms of action and role in hereditary diseases. There are 24 chemicals with strong or sufficient evidence for germ cell aneugenicity providing robust support for the ability of chemicals to induce germ cell aneuploidy. Interference with microtubule dynamics or inhibition of topoisomerase II function are clear characteristics of germ cell aneugens. Although there are mechanisms of chromosome segregation that are unique to germ cells, there is currently no evidence for germ cell-specific aneugens. However, the available data are heavily skewed toward chemicals that are aneugenic in somatic cells. Development of high-throughput screening assays in suitable animal models for exploring additional targets for aneuploidy induction, such as meiosis-specific proteins, and to prioritize chemicals for the potential to be germ cell aneugens is encouraged. Evidence in animal models support that: oocytes are more sensitive than spermatocytes and somatic cells to aneugens; exposure to aneugens leads to aneuploid conceptuses; and, the frequencies of aneuploidy are similar in germ cells and zygotes. Although aneuploidy in germ cells is a significant cause of infertility and pregnancy loss in humans, there is currently limited evidence that aneugens induce hereditary diseases in human populations because the great majority of aneuploid conceptuses die in utero. Overall, the present work underscores the importance of protecting the human population from exposure to chemicals that can induce aneuploidy in germ cells that, in contrast to carcinogenicity, is directly linked to an adverse outcome.

Evaluation of drug prescriptions for pregnant women in the Legal Amazon Region

Abstract Objectives: to evaluate the drug prescriptions for pregnant women in the Legal Amazon during prenatal care. Methods: this is a pharmacoepidemiological, descriptive, retrospective and cross-sectional study. Medical records included sociodemographic variables, prenatal care, most frequent pharmacological classes prescribed, risk classification of drugs and possible drug-drug interactions among pregnant women. Results: a total of 159 records from pregnant women, enrolled in the Unified Health System were used. Most pregnant women began prenatal consultations in the first trimester of pregnancy (53.3%) whereas most of the drugs were prescribed in the second gestational trimester (55.5%). The most used pharmacological classes, classified according to the National List of Essential Drugs were: antianemic preparations (52.9%), vitamins (12.5%) and analgesic (10.6%). According to the risk classification, the highest prevalence of prescribed drugs belongs to category A (46.8%), followed by category C (28.9%), category B (20.0%) and category D (4.3%). Eight possible drug-drug interactions were found, being considered with mild severity, and six classified with moderate risk. Conclusions: the results demonstrate a lack of information regarding prescription drugs for pregnant women and this may endanger maternal and fetal health. It is essential that medical records be an effective therapeutic tool, which should be read, analyzed and reviewed in order to ensure effective and safe medical treatment.

Rare disease registries: potential applications towards impact on development of new drug treatments

BACKGROUND

Low prevalence, lack of knowledge about the disease course, and phenotype heterogeneity hamper the development of drugs for rare diseases. Rare disease registries (RDRs) can be helpful by playing a role in understanding the course of the disease, and providing information necessary for clinical trial design, if designed and maintained properly. We describe the potential applications of a RDR and what type of information should be incorporated to support the design of clinical trials in the process of drug development, based on a broad inventory of registry experience. We evaluated two existing RDRs in more detail to check the completeness of these RDRs for trial design.

RESULTS

Before and during the application for regulatory approval a RDR can improve the efficiency and quality in clinical trial design by informing the sample size calculation and expected disease course. In exceptional circumstances information from RDRs has been used as historical controls for a one-armed clinical trial, and high quality RDRs may be used for registry-based randomized controlled trials. In the post marketing phase of (conditional) drug approval a disease-specific RDR is likely to provide more relevant information than a product-specific registry.

CONCLUSIONS

A RDR can be very helpful to improve the efficiency and quality of clinical trial design in several ways. To enable the applicability and optimal use of a RDR longitudinal data collection is indispensable, and specific data collection, prepared for repeated measurement, is needed. The developed checklist can help to define the appropriate variables to include. Attention should be paid to the inclusion of patient-relevant outcome measures in the RDR from the start. More research and experience is needed on the possibilities and limitations of combining RDR information with clinical trial data to maximize the availability of relevant evidence for regulatory decisions in rare diseases.

Modeling the Age-Associated Decrease in Mortality Rate for Congenital Anomalies of the Central Nervous System Using WHO Metadata From Nine European Countries

Background: In humans, the mortality rate dramatically decreases with age after birth, and the causes of death change significantly during childhood. In the present study, we attempted to explain age-associated decreases in mortality for congenital anomalies of the central nervous system (CACNS), as well as decreases in total mortality with age. We further investigated the age trajectory of mortality in the biologically related category "diseases of the nervous system" (DNS). Methods: The numbers of deaths were extracted from the mortality database of the World Health Organization (WHO) for the following nine countries: Denmark, Finland, Norway, Sweden, Austria, the Czech Republic, Hungary, Poland, and Slovakia. Because zero cases could be ascertained over the age of 30 years in a specific age category, the Halley method was used to calculate the mortality rates in all possible calendar years and in all countries combined. Results: Total mortality from the first day of life up to the age of 10 years and mortality due to CACNS within the age interval of [0, 90) years can be represented by an inverse proportion with a single parameter. High coefficients of determination were observed for both total mortality (R2 = 0.996) and CACNS mortality (R2 = 0.990). Our findings indicated that mortality rates for DNS slowly decrease with age during the first 2 years of life, following which they decrease in accordance with an inverse proportion up to the age of 10 years. The theory of congenital individual risk (TCIR) may explain these observations based on the extinction of individuals with more severe impairments, as well as the bent curve of DNS, which exhibited an adjusted coefficient of determination of R ¯ 2 = 0.966. Conclusion: The coincidence between the age trajectories of all-cause and CACNS-related mortality may indicate that the overall decrease in mortality after birth is due to the extinction of individuals with more severe impairments. More deaths unrelated to congenital anomalies may be caused by the manifestation of latent congenital impairments during childhood.

EUROCAT: an update on its functions and activities

This paper provides an outline of the development and growth of EUROCAT, the European network of congenital anomaly registers. In recent years the network has been through a period of transition and change. The Central Register of data has transferred from the Ulster University to the EU Joint-Research-Centre, Ispra, Italy.The benefits of combining data from across Europe, from different populations and countries are described by the uses to which these data can be put. These uses include:. surveillance of anomalies at a local, regional or pan-European level. pharmacovigilance. registration of rare diseasesNew studies and projects are underway, including EUROlinkCAT (a Horizon 2020 funded data-linkage project), promising a fruitful future in further research of congenital anomalies.

Trends in congenital anomalies in Europe from 1980 to 2012

BACKGROUND

Surveillance of congenital anomalies is important to identify potential teratogens.

METHODS

This study analysed the prevalence of 61 congenital anomaly subgroups (excluding chromosomal) in 25 population-based EUROCAT registries (1980-2012). Live births, fetal deaths and terminations of pregnancy for fetal anomaly were analysed with multilevel random-effects Poisson regression models.

RESULTS

Seventeen anomaly subgroups had statistically significant trends from 2003-2012; 12 increasing and 5 decreasing.

CONCLUSIONS

The annual increasing prevalence of severe congenital heart defects, single ventricle, atrioventricular septal defects and tetralogy of Fallot of 1.4% (95% CI: 0.7% to 2.0%), 4.6% (1.0% to 8.2%), 3.4% (1.3% to 5.5%) and 4.1% (2.4% to 5.7%) respectively may reflect increases in maternal obesity and diabetes (known risk factors). The increased prevalence of cystic adenomatous malformation of the lung [6.5% (3.5% to 9.4%)] and decreased prevalence of limb reduction defects [-2.8% (-4.2% to -1.5%)] are unexplained. For renal dysplasia and maternal infections, increasing trends may be explained by increased screening, and deceases in patent ductus arteriosus at term and increases in craniosynostosis, by improved follow up period after birth and improved diagnosis. For oesophageal atresia, duodenal atresia/stenosis and ano-rectal atresia/stenosis recent changes in prevalence appeared incidental when compared with larger long term fluctuations. For microcephaly and congenital hydronephrosis trends could not be interpreted due to discrepancies in diagnostic criteria. The trends for club foot and syndactyly disappeared once registries with disparate results were excluded. No decrease in neural tube defects was detected, despite efforts at prevention through folic acid supplementation.

Congenital Anomalies: Cluster Detection and Investigation

This work summarizes the main aspects to be considered around birth defects (or congenital anomalies) clusters. Most birth defects (BD), considered individually, fall into the definition of rare diseases (RD), according to their low frequency. Likewise, many RD are congenital, because their manifestations are present at birth or can be even evident before the delivery. It has been estimated that overall 7.9 million children are born each year with serious BD of genetic or partially genetic origin, and additional hundreds of thousands more are born with serious BD of post-conception origin.A "birth defect cluster" can be defined as an unusual aggregation of cases (grouped in place and time) that is suspected to be greater than expected, even though the expected number may not be known. These clusters are incidents or occurrences that let us turn the challenge of identifying the causal agent(s) involved in the origin of such clusters, into an opportunity to exert primary prevention, and thus achieve the ultimate goal of enabling infants being born healthy. Therefore, any program or system involved in BD surveillance and research should devote part of its activities to detect and investigate clusters, to ensure that such opportunity for primary prevention will be conveniently leveraged. Regardless the type of cluster, there are several phases that must be undertaken sequentially for proper control and the maximum benefit for the population: cluster detection, evaluation and investigation, management, adoption of preventive measures, and communication of the results to the public or target population.

Altitude as a risk factor for the development of hypospadias. Geographical cluster distribution analysis in South America

OBJECTIVE

Hypospadias is the most common congenital anomaly affecting the genitals. It has been established as a multifactorial disease with increasing prevalence. Many risk factors have been identified such as prematurity, birth weight, mother's age, and exposure to endocrine disruptors. In recent decades multiple authors using surveillance systems have described an increase in prevalence of hypospadias, but most of the published literature comes from developed countries in Europe and North America and few of the published studies have involved cluster analysis. Few large-scale studies have been performed addressing the effect of altitude and other geographical aspects on the development of hypospadias. Acknowledging this limitation, we present novel results of a multinational spatial scan statistical analysis over a 30-year period in South America and an altitude analysis of hypospadias distribution on a continent level.

METHOD

A retrospective review was performed of the Latin American collaborative study of congenital malformations (ECLAMC). A total of 4,020,384 newborns was surveyed between 1982 and December 2011 in all participating centers. We selected all patients with hypospadias. All degrees of clinical severity were included in the analysis. Each participating center was geographically identified with its coordinates and altitude above sea level. A spatial scan statistical analysis was performed using Kulldorf's methodology and a prevalence trend analysis over time in centers below and above 2000 m.

RESULTS

During the study period we found 159 hospitals in six different countries (Colombia, Bolivia, Brazil, Argentina, Chile, and Uruguay) with 4,537 cases of hypospadias and a global prevalence rate of 11.3/10,000 newborns. Trend analysis showed that centers below 2000 m had an increasing trend with an average of 10/10,000 newborns as opposed to those centers above 2000 m that showed a reducing trend with an average prevalence of 7.8 (p = 0.1246). We identified clusters with significant increases of prevalence in five centers along the coast at an average altitude of 219.8 m above sea level (p > 0.0000). Reduction in prevalence was found in clusters located in two centers on the Andes mountains. Altitude of 2,000 m was associated with hypospadias (Figure), with an OR 0.59 (0.5-0.69). There are ethnic arguments to support our results supported by protective polymorphism distribution in high lands.

CONCLUSION

Altitude above 2,000 m is suggested to have a protective effect for hypospadias. Specific clusters have been identified with increased risk for hypospadias. Environmental risk factors in these areas need to be further studied given the association seen between altitude and the distribution of more severe cases.

Preventing birth defects: The value of the NBDPS case-control approach

Birth Defect Registries provide a basis for epidemiological research into risk factors, thus facilitating a growing understanding of what causes congenital anomalies and how one might target preventive public health actions and reduce inequalities. The National Birth Defects Prevention Study (NBDPS) has used 10 U.S. registries as a basis for a large case-control study. This commentary reviews its methodology and selected areas of output. The strengths of NBDPS lie in the quality of diagnostic coding and classification of birth defects and its size. The sources of bias in NBDPS data relate particularly to retrospective exposure ascertainment entailing a long period of recall, incomplete ascertainment of terminations of pregnancy for fetal anomaly, and unknown bias in case selection. NBDPS results have shown the protective effect of healthy dietary patterns, but have not been as informative as expected in relation to furthering understanding of the protective effect of folic acid. NBDPS medication studies are making important contributions to addressing the gap in existing evidence systematically across a wide range of birth defects, but are challenged by the quality of information on exposure, dose and underlying disease condition, and the interpretation of results of multiple testing. Studies of environmental contaminants in collaboration with experts in exposure assessment have linked addresses to residential exposure measures, using the advantages of information on residential history and confounders, but are challenged by the need to consider exposure mixtures. NBDPS could increase its public health impact by placing more emphasis on socioeconomic inequalities.

Using scan statistics for congenital anomalies surveillance: the EUROCAT methodology

Scan statistics have been used extensively to identify temporal clusters of health events. We describe the temporal cluster detection methodology adopted by the EUROCAT (European Surveillance of Congenital Anomalies) monitoring system. Since 2001, EUROCAT has implemented variable window width scan statistic for detecting unusual temporal aggregations of congenital anomaly cases. The scan windows are based on numbers of cases rather than being defined by time. The methodology is imbedded in the EUROCAT Central Database for annual application to centrally held registry data. The methodology was incrementally adapted to improve the utility and to address statistical issues. Simulation exercises were used to determine the power of the methodology to identify periods of raised risk (of 1-18 months). In order to operationalize the scan methodology, a number of adaptations were needed, including: estimating date of conception as unit of time; deciding the maximum length (in time) and recency of clusters of interest; reporting of multiple and overlapping significant clusters; replacing the Monte Carlo simulation with a lookup table to reduce computation time; and placing a threshold on underlying population change and estimating the false positive rate by simulation. Exploration of power found that raised risk periods lasting 1 month are unlikely to be detected except when the relative risk and case counts are high. The variable window width scan statistic is a useful tool for the surveillance of congenital anomalies. Numerous adaptations have improved the utility of the original methodology in the context of temporal cluster detection in congenital anomalies.