Selective reduction (or fetal reduction) is the practice of aborting one or more fetuses in a multifetal pregnancy. Such an abortion procedure is often performed after a congenital defect has been identified. Prenatal diagnostic testing may determine that some fetuses have chromosomal defects or a greater chance of genetic diseases, and those fetus(es) are then targeted in selective reduction. Selective reduction is also used to reduce a higher-order multiple pregnancy (one with three or more fetuses) to a twin or singleton pregnancy.