Confined placental mosaicism in short term culture

Abstract

Finding of fetal chromosomal mosaicism complicates genetic counseling, as well as pregnancy management. The aim of this study was to determine the risk of confined placental mosaicism in short term culture of chorionic villous samples. We conducted a retrospective review of karyotype analysis results obtained after chorionic villous sampling (CVS) in two years period. A 420 samples of chorionic villi were taken transabdominally and obtained by a semidirect method (overnight incubating culture). All fetuses with CVS mosaicism were under the intensive perinatal care. In all cases of chromosome mosaicism the additional karyotyping was performed from fetal blood samples after 22nd gestational week in order to exclude true fetal mosaicism. After delivery newborns were examined by experienced pediatrician. From 420 analyzed samples in 11 (2,6%) cases we found placental mosaicism. No anomalies were seen in genetic sonogram of this fetuses and mosaicism was confirmed only in one case. Confined placental mosaicism (CPM) was found in 2,1% (9/420) of all analyzed cases, and it made 90% of all placental mosaicism. In 60% (6/10) of placental mosaicism cases we found mosaicism with single aberrant cell. Trisomy 21 mosaicism was the most frequent aberration found in 30% of cases. Finding of mosaicism in chorionic villi sample is at special importance for genetic counseling, because every case has to be reveled individually regarding the type and level of mosaicism. Anyway, in every case of placental mosaicism intensive antenatal monitoring is necessary, with additional chromosome analysis from different tissue in consideration of previous findings.