information about a fetus can
be obtained by analysis of amniotic
fluid or the shed cells in the amniotic
cavity. In the amniocentesis procedure,
is withdrawn by means of a needle inserted through the amnion
into the placental sac. Biochemical
analysis of the
fluid itself may indicate a genetic condition (e.g., high levels of
may indicate PKU).
Karyotypic analysis of shed
fetal cells can be used
gender (Barr body
determination), or more specific karyotypic
conditions (e.g., Down Syndrome
Direct analysis of DNA by various RFLP and PCR
much more rapid diagnosis, an important consideration in deciosions
The amniocentesis procedure entail some risk of
damage to the mother and/or fetus. In general, in the absence of
indications of specific genetic risk from family history, amniocentesis
is not recommended as a general prenatal screen.
Figure © 2002 by
al. ; text © 2010 by Steven M.