ABSTRACT
Amniocentesis involves the aspiration of amniotic fluid from the amniotic sac via a needle inserted through the maternal abdomen. It is the commonest prenatal diagnostic procedure in the UK. Amniocentesis is also used for the diagnosis of single-gene disorders. An ever-increasing range of invasive techniques is being developed to facilitate the diagnosis of chromosomal and single-gene defects, metabolic disorders, intrauterine infection, fetal anaemia, thrombocytopenia and some structural problems. Developments in techniques employing multiplex polymerase chain reaction (PCR) have enabled reliable prenatal diagnosis of fetal blood groups and fetal aneuploidy. Using PCR techniques, amniocentesis can also be used to facilitate the diagnosis of certain congenital infections, such as cytomegalovirus and toxoplasmosis. Fetal blood sampling is also vital in the diagnosis of fetal haematological problems such as anaemia and thrombocytopenia. It has also been used to assess the acid-base status of the fetus in growth restriction, but non-invasive biophysical methods and Doppler studies are more routinely used.
