Medical Genetics A Amniocentesis Amniocentesis is the withdrawal of amniotic fluid from the amniotic sac surrounding the fetus. for over two decades this has been the primary technique utilised for the diagnosis of fetal genetic disordersMedical Genetics A. Amniocentesis Amniocentesis is the withdrawal of amniotic fluid from the amniotic sac surrounding the fetus. For over two decades this has been the primary technique utilised for the diagnosis of fetal genetic disorders