Sonographic markers for Down's syndrome have been useful in the identification of affected fetuses. In this study, we evaluated the accuracy of an expanded scoring index that included recently described sonographic markers as well as maternal age to optimize identification of fetuses with Down's syndrome.
Over a 27 month period, we performed 4075 genetic amniocenteses for advanced maternal age or an abnormal triple panel. Prior to each amniocentesis, a complete sonographic assessment of the fetus was performed including a structural survey and fetal biometry. Each patient was assigned a score based on the sonographic markers in a previously reported scoring system, modified by the addition of an echogenic intracardiac focus. The sonographic scoring system was then combined with the assignment of additional points based on maternal age. Karyotypic results were obtained subsequent to the scans, and Down's syndrome fetuses and a control group of normal fetuses were compared.
Fifty-three fetuses with Down's syndrome were identified by karyotype and compared to a control group of 177 normal fetuses. A score of ≥ 2 as a criterion for a positive test resulted in the identification of 75.4% of fetuses with Down's syndrome, with a 5.7% false-positive rate. A score of ≥ 1 increased the sensitivity to 83.0%, with a false-positive rate of 17.5%. The age-adjusted modification resulted in the identification of 86.8% of fetuses with Down's syndrome, with a false-positive rate of 27.1%. It is for the individual patient and her practitioner to weigh the risks and benefits in selecting her options for prenatal diagnosis. Copyright © 1997 International Society of Ultrasound in Obstetrics and Gynecology