Critical issues in prenatal maternal serum alpha-fetoprotein screening for genetic anomalies.

Prenatal screening, in this Clinical Opinion article, is defined as a population-based search for subgroups of pregnancy that by virtue of their maternal serum alpha-fetoprotein levels may be at increased risk for genetic anomalies. The identification of subgroups at risk for neural tube defects, ventral wall defects, and chromosomal trisomies presents clinicians with unprecedented information and issues, including the biomedical basis for prenatal screening, the distinction between screening and diagnosis, and the decision-making function of the patient. The interest and, perhaps, ambivalence of the clinical community to prenatal screening are understandable. Obstetricians ordering prenatal screens are challenged by medical data associated with epidemiology, pathology, and genetics, including: prevalence of disease, interpretive biochemical reporting, and the assessment and communication of patient-specific risks. Obstetricians ordering screens will be called on to provide information generally used by other specialists at other stages of care. What information, how it is biomedically determined, its form for communication to patients, and pitfalls in the process are discussed.