Impact of abnormal second-trimester maternal serum single, double, and triple screening on patient choices about prenatal diagnosis.

The development of multiple-marker biochemical screening has increased the percentage of aneuploidies detected for all age groups and has also increased the abnormality/amniocentesis ratio from about 1 in 85 for maternal serum alpha-fetoprotein alone (single screening) to about 1 in 50 for either maternal serum alpha-fetoprotein plus human chorionic gonadotropin (double screening) or maternal serum alpha-fetoprotein combined with human chorionic gonadotropin and unconjugated estriol (triple screening). We evaluated the decisions to have or decline amniocentesis of 985 patients 'at risk' by either single, double, or triple screening, as multiple markers were phased in over a 3-year period. The patient acceptance of the procedure did not change (approximately 80%) either by actual risk or type of biochemical screening. The labeling of 'at risk' status is more important than actual numerical risks, and the patient perception of risk status must be considered in counseling.