RESUMEN
<p><b>OBJECTIVE</b>Spinal muscular atrophy (SMA) is a common and fatal autosomal recessive disorder. Approximately 94% of SMA patients are caused by homozygous deletion of SMN1 gene. SMA carrier screening is recommended considering the high carrier frequency (1 in 35-50) as well as severity of the disease.</p><p><b>METHODS</b>A prospective population-based cohort study was carried out on 4719 pregnant women from Shanghai region. Copy numbers of SMN1 and SMN2 genes were effectively determined with denaturing high performance liquid chromatography (DHPLC) technique. The method has detected 94% of SMA cases with deletion or conversion of the SMN1 genes.</p><p><b>RESULTS</b>Ninety SMA carriers with only one copy of the SMN1 gene were identified among the 4719 pregnant woman. The carrier rate was 1.9%. Respectively, 1.2% and 0.6% of the carriers were caused by SMN1 gene deletion and SMN1 gene conversion.</p><p><b>CONCLUSION</b>Through this study, we have determined the frequency of SMA mutation carriers in a population of pregnant women. The result may provide a basis for genetic counseling in order to reduce the rate of SMA affected births.</p>