Dr. Thaddeus Waters of the Women's Health division at Loyola talks about chorionic villus sampling, a highly accurate prenatal genetic test. He explains that there are two chromosomal tests now available, amniocentesis and CVS. Amniocentesis is generally performed after 15 weeks of pregnancy and CVS is offered between 11 and 13 weeks. This test can determine if an aneuploidy, or abnormal number of chromosomes, is present. It can also determine if a molecular issue exists. If an abnormality is discovered, such as a heart deformity, Loyola has specialists on staff to help the couple with any needed care or surgery. For more information or to make an appointment, please call 888-LUHS-888 (888-584-7888).