Interphase fluorescence in situ hybridization assisting in prenatal counseling for amniocentesis karyotyping-detected fetal mosaicism

ObjectiveTo evaluate how interphase fluorescence in situ hybridization (FISH) played a role in genetic counseling when encountering prenatally detected fetal mosaicism cases.Materials and methodsWe retrospectively reviewed 17 cases of amniotic fluid specimens diagnosed with Level III chromosome mosaicism using in situ coverslip culture method. Among them, seven received additional interphase FISH tests; five were related to autosomal mosaicism and two others were due to sex chromosomes.ResultsIn the autosome group, one couple chose to terminate the pregnancy due to a high percentage of trisomy 21 cells (48.1%) shown on interphase FISH; in the gonosome group, one case chose termination as FISH exhibited as high as 80% of XXYY cells.ConclusionPerforming interphase FISH on uncultured amniocytes for cases detected with mosaicism by traditional amniotic fluid culture provided quick confirmation of the karyotyping results; additionally, obtaining information about the extent of the abnormality involved using interphase FISH could also play a role in counseling patients on the decision making concerning the future of their pregnancies.