We evaluated the prenatal diagnosis utilization patterns of advanced maternal age (AMA) patients who underwent serum screening to assess how screening results correlated with their decisions regarding amniocentesis. A 6-year review (1994-1999) of laboratory records identified 2,456 AMA patients who underwent multiple-marker serum screening. The relationship between screening results and patients' decisions on whether or not to undergo amniocentesis was assessed. Among the 841 AMA patients with positive screens, more than half (52%) declined amniocentesis. Of the 1,615 patients with negative serum screening results, 208 (13%) opted for amniocentesis. We concluded that decisions by AMA patients regarding amniocentesis may not always correlate clinically with maternal serum screening results. Possible explanations, including how the state of informed consent may or may not contribute to these decisions, are discussed. It is suggested that understanding the reasons for these decisions may identify opportunities for improving service delivery to all pregnant patients considering prenatal testing. Use of a questionnaire is proposed as one mechanism for gaining a clearer understanding of the possible factors contributing to AMA patient decisions.