High Birth Prevalence Rates for Congenital Anomalies in South American Regions:

Clusters of rare disorders and congenital anomalies in South America

Objective

To map geographic clusters of rare disorders and congenital anomalies reported in South America.

Methods

Qualitative systematic review conducted in Medline/PubMed, Lilacs, and Scielo electronic databases to identify studies meeting eligibility criteria. The strategy resulted in 1 672 unique articles, from which 164 were selected for full reading by a pair of reviewers.

Results

Fifty-five articles reported at least one cluster of genetic disorders or congenital anomalies in South American territory. From these papers, 122 clusters were identified, of which half (61) were related to autosomal recessive disorders. Sixty-five (53.3%) of the clusters were located in Brazil.

Conclusions

The results of the review reinforce that rare diseases and congenital anomalies can occur in a non-random way in space, which is discussed in the perspective of the complex history of formation, social organization, and genetic structure of the South American population. Mapping clusters in population medical genetics can be an important public health tool, given that such places concentrate cases of rare diseases that frequently require multiprofessional, specialized care. Therefore, these results can support important agendas in public health related to rare diseases and congenital anomalies, such as health promotion and surveillance.

Análise espacial das anomalias congênitas do sistema nervoso

Resumo Introdução A anomalia congênita do sistema nervoso ocorre durante o desenvolvimento embrionário. O território pode ser um fator determinante e esse conhecimento é importante para o planejamento de ações ou intervenções em saúde pública. Objetivo Detectar aglomerados espaciais da ocorrência das anomalias congênitas do sistema nervoso e caracterizá-las de acordo com as variáveis do Sistema de Informações sobre Nascidos Vivos. Método Estudo ecológico em que foram utilizados os dados do Sistema de Informações sobre Nascidos Vivos no Estado da Paraíba, período entre 2014 e 2016. Para a análise dos dados foram empregados a Razão de Incidências Espacial, a estatística Scan e o teste de Friedman. Resultados Foi constatado que nos anos de 2014 e 2016 os aglomerados espaciais estavam espalhados pelo Estado, enquanto no ano de 2015 ocorreu uma maior concentração desses ao noroeste do Estado. Conclusão A detecção dos aglomerados espaciais pode auxiliar os gestores na identificação de áreas prioritárias no cuidado à saúde de crianças com anomalias congênitas do sistema nervoso.

Congenital anomalies in Rio Grande do Sul State: a time series analysis

INTRODUCTION

In Rio Grande do Sul Sate (Brazil), the incidence of congenital anomalies ranges from 10 to 15/1,000 live births. Identifying risk factors can change congenital anomalies frequency and neonatal mortality. This paper intends to analyze temporal variation of congenital anomalies in the State of Rio Grande do Sul, from 2005 to 2014, and to identify the factors associated with its occurrence.

METHOD

This is a descriptive, time series study based on secondary data on congenital anomalies and sociodemographic and health variables of mothers and newborns living in Rio Grande do Sul, from 2005 to 2014.

RESULTS

In the period surveyed, there were 1,386,803 births of mothers living in Rio Grande do Sul, and the cases diagnosed with congenital anomalies corresponded to a general average rate of 9.2 per thousand cases, with a greater rate in the group of mothers of newborns whose Apgar score was lower than seven; who had a weight equal to or lower than 1,500 grams; with a gestational age equal to or lower than 31 weeks and living in the metropolitan region. The most frequent types of congenital anomalies were those located in the musculoskeletal system, the nervous system and the circulatory system.

CONCLUSION

These data warn us about the change in the epidemiological profile of mothers of children with congenital anomalies, thereby indicating the groups at greatest risk.

Geographic clusters of congenital anomalies in Argentina

Geographical clusters are defined as the occurrence of an unusual number of cases higher than expected in a given geographical area in a certain period of time. The aim of this study was to identify potential geographical clusters of specific selected congenital anomalies (CA) in Argentina. The cases were ascertained from 703,325 births, examined in 133 maternity hospitals in the 24 provinces of Argentina. We used the spatial scan statistic to determine areas of Argentina which had statistically significant elevations of prevalence. Prenatal diagnosis followed by referral of high-risk pregnancies to high complexity hospitals in a hospital-based surveillance system can create artifactual clusters. We assessed the referral bias by evaluating the prevalence heterogeneity within each cluster. Eight clusters of selected CAs with unusually high birth prevalence were identified: anencephaly, encephalocele, spina bifida, diaphragmatic hernia, talipes equinovarus, omphalocele, Cleft lip with or without cleft palate (CL/P), and Down syndrome. The clusters of Down syndrome and CL/P observed in this study match the previously reported clusters. These findings support local targeted interventions to lower the prevalence of the CAs and/or further research on the cause of each cluster. The clusters of spina bifida, anencephaly, encephalocele, omphalocele, congenital diaphragmatic hernia, and talipes equinovarus may be influenced by prenatal diagnosis and referral to high complexity hospitals.

Descriptive analysis of high birth prevalence rate geographical clusters of congenital anomalies in South America

BACKGROUND

The birth prevalence rate (BPR) of congenital anomalies (CAs) is heterogeneous and exhibits geographical and sociocultural variations throughout the world. In South America (SA), high birth prevalence regions of congenital anomalies have been observed. The aim of this study was to identify, describe, and characterize geographical clusters of congenital anomalies in SA.

METHODS

This observational descriptive study is based on clinical epidemiological data registered by the Latin-American Collaborative Study of Congenital Malformations network. Between 1995 and 2012, a total of 25,082 malformed newborns were ascertained from 2,557,424 births at 129 hospitals in SA. The spatial scan statistic was used to determine geographical regions with high BPR of CAs. The BPR was obtained with a Poisson regression model. Odds ratios were estimated for several risk factors inside the geographical clusters.

RESULTS

We confirmed the existence of high BPR regions of CAs in SA. Indicators of low socioeconomic conditions, such as a low maternal education, extreme age childbearing, infectious diseases, and medicine use during pregnancy were detected as risk factors inside these regions. Native and African ancestries with high frequency of consanguineous marriages could explain partially these high BPR clusters.

CONCLUSION

The recognition of clusters could be a starting point in the identification of susceptibility genes associated with the occurrence of CA in high BPR regions.