Alpha-fetoprotein.

The past year has seen major challenges to existing maternal serum alpha-fetoprotein testing protocols for both neural tube defects and chromosomal anomalies. These challenges are reviewed along with the physiology of alpha-fetoprotein; the use of amniocentesis, ultrasonography, and additional serum markers in women with elevated alpha-fetoprotein levels; and epidemiologic implications of maternal serum alpha-fetoprotein screening.