Abstract: Objective To explore the prenatal diagnosis of chromosome moasic. Methods The clinical data of a pregnant woman whose ultrasound scans suggested fetal ventricular septal defect and single umbilical artery were retrospectively analyzed. As peripheral venous blood for serological screening indicated high risk of trisomy 21, the woman received non-invasive prenatal testing(NIPT)in another hospital at 17⁺² weeks of gestation. For further prenatal diagnosis, she received amniocentesis, karyotype analysis, chromosome microarray analysis(CMA), 6pter/6qter probe fluorescence in situ hybridization(FISH), and CMA of fetus placenta and skin tissue at 25⁺⁵ weeks of gestation. A total of 82 cells were counted and 5 cells were analyzed in karyotype analysis of amniotic fluid cells. Results NIPT suggested a low risk of trisomy 21, 18 and 13 syndromes. The karyotype of amniotic fluid was 47,XN,+del(6)(p21.1)［24］/46,XN［58］. CMA indicated normal in the uncultured amniotic fluid cells, but 6q trisomy moasic in the cultured cells. FISH analyzed 100 uncultured cells, among which 89 were normal, and 6 were 6q trisomy. FISH test was normal. No abnormality was found in CMA of the placenta and skin tissue of the induced fetus. Conclusion Based on the results of fetal ultrasound, karyotype analysis and molecular genetic testing, the fetus was determined to be moasic with a very low proportion of trisomy 6q, and the risk of false negative was reduced.

Key words: Chromosome moasic, Prenatal diagnosis, Karyotype analysis, Chromosome Microarray, Fluorescence in situ hybridization