The triple test, also called triple screen, the Kettering test or the Bart's test, is an investigation performed during pregnancy in the second trimester to classify a patient as either high-risk or low-risk for chromosomal abnormalities (and neural tube defects). The triple marker screen test analyzes how likely an unborn baby is to have certain genetic disorders. It is also known as a multiple marker test. The exam measures the levels of three important substances in the placenta: alpha-fetoprotein (AFP), human chorionic gonadotropin (HCG), and estriol. The results of the triple marker screen test show the likelihood of an infant having a genetic disorder such as Down syndrome or spina bifida.