Explain why geneticists believe that almost all chromosomally abnormal embryos and fetuses are ...

Comparison of the number of chromosomal abnormalities detected by CVS (performed at 8 to 10 weeks of gestation) versus amniocentesis (at 16 weeks of gestation) shows that the abnormalities detected by CVS are two to five times more common than those detected by amniocentesis, which in turn are about two times more common than those found in newborns. This decrease in the frequency of chromosomal abnormalities during pregnancy provides evidence that almost all chromosomally abnormal embryos and fetuses are eliminated as pregnancy progresses.