Detection and Clinical Significance of Chromosomal Mosaicism in Prenatal Diagnosis: A Retrospective Study From a Prenatal Diagnosis Center.

BACKGROUND: To evaluate the detection capabilities of prenatal screening and diagnostic methods for fetal chromosomal mosaicism and analyze associated pregnancy outcomes. METHODS: This retrospective study included 79 cases of fetal chromosomal mosaicism identified by karyotyping among 8106 women undergoing prenatal diagnosis. Sensitivity of screening methods (first-trimester serum screening, second-trimester serum screening, and noninvasive prenatal testing (NIPT)) and concordance of diagnostic methods (chromosomal microarray analysis (CMA), multiple STR locus analysis technique (QF-PCR)) with karyotyping were assessed. Pregnancy outcomes were analyzed. RESULTS: NIPT demonstrated significantly higher sensitivity (90.74%) compared with first-trimester serum screening (57.41%) and second-trimester serum screening (39.29%) (p < 0.001). CMA showed high concordance with karyotyping (90.00%), whereas QF-PCR exhibited significantly lower concordance (58.21%) (p < 0.001). The pregnancy termination rate was 57.14% (40/70). All trisomy 21 and trisomy 13 mosaicism cases resulted in termination, while decisions regarding other autosomal and sex chromosome mosaicism were more variable. CONCLUSION: NIPT outperforms traditional serum screening for detecting chromosomal mosaicism, though karyotyping remains essential for confirmation. CMA aligns well with karyotyping, particularly for low-level mosaicism. The high termination rate underscores the critical need for multidisciplinary genetic counseling integrating genetic, imaging, and clinical data.