Trisomy 21: 91% detection rate using second-trimester ultrasound markers

Abstract

Objectives: To examine cardiovascular and non-cardiovascular prenatal ultrasound markers and determine which markers physicians of varying skill levels could use to identify fetuses with trisomy 21.

Methods: Eighty second-trimester fetuses with trisomy 21 and 2000 controls underwent real-time plus color Doppler examination of cardiovascular and non-cardiovascular systems followed by amniocentesis. Non-cardiac markers were central nervous system malformations (CNS); choroid plexus cysts (CPC); abnormal nuchal skin fold (NSF); hyperechoic bowel (HB); and pyelectasis (PY). Cardiac markers consisted of ventricular septal defect, right-to-left chamber disproportion (RL); tricuspid regurgitation; mitral regurgitation (MR); pericardial effusion; and outflow tract abnormalities (OFT). Multinomial logistic regression was used to identify interactivity between the markers. Logistic regression was utilized to identify which combinations of markers significantly contributed to the identification of fetuses with trisomy 21 and to compute the likelihood ratio.

Results: All but three markers (CPC, MR, OFT) contributed significantly to the identification of 91% of fetuses with trisomy 21 with a false-positive rate of 14%. When only non-cardiovascular markers were examined, all but CPC contributed to the identification of 60% of fetuses with trisomy 21 with a false-positive rate of 5.9%. Combining right-to-left chamber disproportion with CNS, NSF, HB and PY identified 75% of fetuses with trisomy 21 with a false-positive rate of 6.4%. All markers were independent predictors of trisomy 21 except RL and NSF.

Conclusion: Ultrasound can detect between 60 and 91% of fetuses with trisomy 21 depending upon which markers are selected for evaluation.