Down Syndrome is the most common cause mental deficiency of genetic etiology, present in approximately one case per 600-700 births, making it the most common condition of aneuploidy compatible with life. In 95% of cases, is attributed to free trisomy of chromosome 21 resulting from maternal meiotic nondisjunction.It is well established that advanced maternal age is a risk factor for non-disjunction, however other etiological factors independent of maternal age are also related to the occurrence of Down syndrome. Among these factors, is hypomethylation of centromeric DNA as a consequence of abnormal folate metabolism, and polymorphisms in genes encoding enzymes involved in metabolism, have been suggested as maternal risk factors for the syndrome. Genetic polymorphisms may alter the resulting products of the folate metabolic pathway and result in DNA hypomethylation, genomic instability and reduced DNA repair capacity. Studies investigating the association between genetic polymorphisms involved in folate metabolic pathway and Down syndrome, report contradictory or inconclusive results. Therefore, the aim of this study is to determine, through systematic review and meta-analysis, the presence of polymorphisms in folate metabolic pathway have genetic risk factors for birth mothers of children with Down syndrome, based on best available evidence in literature.
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