Discordant chromosome placental mosaicism in a dichorionic twin pregnancy

摘要

Chorionic villus sampling (CVS) is now well established as an invasive test for prenatal diagnosis of chromosome abnormalities and some authors argue that this first-trimester procedure has several advantages over mid-trimester amniocentesis in twin pregnancies [Brambati et al., 2001]. Since twin gestations seem to have a higher risk of chromosome aberrations when compared to singleton pregnancies, some centers now offer the possibility of first-trimester prenatal diagnosis using CVS, including molecular rapid aneuploidy (MRA) testing by QF-PCR or multiplex ligation-dependent probe amplification (MLPA). CVS may provide the possibility of an earlier result which may be crucial for patient reassurance and pregnancy management but has the disadvantage of the occasional presence of placental mosaicism, in around 1-2% of cases, that can result from analyzing a tissue chromosomally different from that of the fetus [Ledbetter et al., 1992; Farra et al., 2000].