The Use of Color Doppler Ultrasound to Identify Fetuses at Increased Risk for Trisomy 21: An Alternative for High‐Risk Patients Who Decline Genetic Amniocentesis

Objective To compare color Doppler ultrasound with realtime ultrasound to determine whether it increased the identification of fetuses with trisomy 21. Methods Consecutive fetuses with a second trimester risk greater than 1:270 for trisomy 21 were examined with real-time ultrasound (n = 1028) or real-time plus color Doppler ultrasound (n = 1028) before second trimester genetic amniocentesis. The type of abnormal ultrasound findings were compared between fetuses with normal and abnormal chromosomes. Using the Bayes theorem, the ultrasound-adjusted maternal age-related risk (posterior risk) for trisomy 21 was computed after a normal or abnormal real-time plus color Doppler examination. Results A significantly greater number of fetuses with trisomy 21 (87% [13 of 15] versus 29% [5 of 17], P < .002) were identified with real-time plus color Doppler than with real-time ultrasound. Color Doppler ultrasound identified a significantly higher rate of cardiovascular abnormalities in fetuses with trisomy 21 (60% [9 of 15] versus 12% [2 of 17], P < .008) than did real-time ultrasound. Identification of abnormal fetal anatomy using real-time plus color Doppler in patients 35 years and older increases the likelihood of detecting trisomy 21. A normal real-time plus color Doppler examination of the fetus decreases the risk for trisomy 21 to less than 1:270 until the maternal age of 42, above which the risk for trisomy 21 is greater than 1:270. Conclusion Real-time plus color Doppler ultrasound examination of the fetus is an alternative for the identification of trisomy 21 for patients who may decline genetic amniocentesis based on their age-related risk.