Screening and Prenatal Diagnosis of Spinal Muscular Atrophy in 13,500 Pregnant Women in the Changzhi Area

Background:Spinal muscular atrophy (SMA) is a fatal autosomal recessive hereditary neuromuscular disorder. Definitive treatment remains limited, and the carrier frequency in the general population is relatively high. This study aims to determine the carrier frequency of SMA and to characterize mutation types in the survival motor neuron 1 (SMN1) gene among pregnant women in the Changzhi area. It also evaluates the clinical value of large-scale carrier screening combined with prenatal diagnosis.Methods:Real-time fluorescence quantitative polymerase chain reaction (PCR) was used to detect the copy numbers of exon 7 (E7) and exon 8 (E8) of the SMN1 gene in pregnant women for carrier screening, with simultaneous testing of their spouses. For couples in which both partners were carriers, invasive prenatal diagnosis of high-risk fetuses was performed using multiplex ligation-dependent probe amplification (MLPA) on amniotic fluid or on chorionic villous sampling. PCR–melting curve analysis was used to recheck some initially positive pregnant women to exclude false positive results and to compare the accuracy of the detection reagents.Results:Among 13,500 pregnant women, a total of 338 SMA carriers were identified, corresponding to a carrier frequency of 1/40 (2.50%). The distribution of mutation types was as follows: 217 cases (64.20%) of E7+E8 heterozygous deletion, 43 cases (12.72%) of E7 heterozygous deletion, 77 cases (22.78%) of E8 heterozygous deletion, and 1 case (0.30%) of E8 homozygous deletion. A total of four couples in which both partners were SMA carriers were identified. This study employed Tianlong and Wuseshi reagents for clinical screening. The Tianlong reagent showed higher accuracy and concordance in the detection of SMN1 E7 and E8 copy numbers. The SMA carrier frequency in the Changzhi area was higher than that in the Gansu and Jiangsu regions (χ2 = 14.964 and 10.868, respectively; p < 0.05). However, no statistically significant difference was observed compared with Shenzhen (p > 0.05).Conclusions:The SMA carrier frequency in the Changzhi region was 2.50%, with E7+E8 heterozygous deletion as the predominant mutation type. Large-scale SMA gene screening in pregnant women, together with early diagnosis in high-risk groups, may support prevention strategies. This study did not include a formal cost-benefit analysis. The discussion of economic significance is merely descriptive, and the conclusions should be interpreted with caution.