A routine diagnostic procedure for pregnant women to determine whether or not their fetuses have gross chromosomal anomalies. This screening procedure is also called maternal serum alpha-feto protein (MSAFP) testing. The testing is comparatively inexpensive but not as reliable as amniocentesis or chorionic villi sampling. With AFP sampling, blood is drawn from a pregnant woman in order to determine the amount of alpha-feto protein that has leaked into her system from her unborn child. Unusually high or low amounts of AFP relative to the stage of pregnancy indicate that there may be specific kinds of genetic defects. Specifically, it may indicate the likelihood of Down syndrome, neural tube defects, abdominal wall defects, and trisomy 18. Low AFP levels are associated with Down syndrome, while high levels are indicative of neural tube defects. The amounts of other diagnostic fetal chemicals (hCG and estriol) also are measured in expanded AFP screening or triple-screening.