in a survey of pregnancies , in which a chromosomal abnormality was diagnosed by amniocentesis but in which the mother did not undergo an abortion , the spontaneous fetal death rate after amniocentesis for 21 fetuses with down 's syndrome was 24 per cent ( or 21 per cent , considering 19 singletons only ) .
C0008625
chromosomal abnormality
C0013080
down 's