Antenatal Results and Choices - ARC - UK Charity offering information and support for those considering, going through or making decisions based on the results of pre-natal tests. Perinatology.com - Reference for the clinical geneticist. How Stuff Works - Illustrated narrative describing an assortment of testing decisions. Mother and Child - Discusses purpose and procedure of chorionic villus sampling. Includes list of advantages and disadvantages compared to amniocentesis. University of Pennsylvania - Information regarding chorionic villi sampling. NT Laboratories - Offers information on a variety of prenatal tests, including amniocentisis, and the ultra-screen. CDC: Prenatal Discussion of HIV Testing - Testing for the HIV virus during pregnancy.