J Obstet Gynaecol Res 2015 Jan 28;41(1):141-4. Epub 2014 Aug 28.
Shikoku Medical Center for Children and Adults, General Perinatal Medical Center, Zentsuji, Japan; Department of Obstetrics and Gynecology, Tokushima University Hospital, Tokushima, Japan.
We report a case of non-mosaic trisomy 20 detected prenatally by amniocentesis during the 16th week of pregnancy. Fetal blood sampling showed a normal karyotype and no fetal, neonatal or infant abnormalities were observed. Amniotic fluid cell karyotyping revealed a trisomy 20 (47,XY,+20) with 100% trisomic cells (38/38); however, a subsequent cordocentesis revealed a normal male karyotype. Moreover, a follow-up ultrasonographic examination did not reveal any major congenital malformations, and a healthy male infant was delivered subsequently at an appropriate gestational age without obvious anomalies. Cytogenetic analysis of blood lymphocytes from the infant revealed a normal karyotype, but cultured cells from the term placenta showed a mosaic karyotype 47,XY,+20/46,XY with 88% trisomic cells (44 of 50). Furthermore, no anomalies or developmental delays were observed in the neonatal period, thus suggesting two possibilities: confined placental mosaicism with the presence of normal and abnormal cell lineages, or generalized mosaicism affecting a limited number of tissues in both the placenta and fetus.