SUBTLE ULTRASONOGRAPHIC ANOMALIES - DO THEY IMPROVE THE DOWN-SYNDROMEDETECTION RATE

OBJECTIVE: Our purpose was to determine whether the identification of subtle anomalies further improves Down syndrome detection over standar d ultrasonographic biometry and the detection of gross morphologic def ects. STUDY DESIGN: The screening efficiency of clinodactyly, dilated renal pelvis (greater than or equal to 4 mm), echogenic bowel, mild ve ntriculomegaly (greater than or equal to 10 to 15 mm), and two-vessel cord was determined prospectively in midtrimester fetuses at amniocent esis. The screening efficiency of increased nuchal thickness and short ened long-bone length (standard biometry) and gross morphologic defect s was determined for comparison. Multiple backward stepwise regression analysis was used to determine which subtle anomalies significantly c orrelated with Down syndrome detection rate and whether they increased Down syndrome detection over that with standard biometry and morpholo gic defects. RESULTS: Although all subtle anomalies except two-vessel cord correlated with the presence of Down syndrome on univariate analy sis, only echogenic bowel (Wald chi(2) = 15.0211, p = 0.0001) and clin odactyly (Wald chi(2) = 9.4273, p = 0.002) persisted in regression ana lysis of the subtle anomaly group. When either of the above-described anomalies was present, the detection rate for Down syndrome was 28.6%, p < 0.00001. For the combination of standard biometry (either increas ed nuchal thickness or short humerus) or gross anatomic defect, Down s yndrome detection rate was 53.3% (p < 0.00000001). This increased to 6 3.2% (p < 0.00000001) when subtle anatomic defects (either echogenic b owel or clinodactyly) were included in the definition of an abnormal s onogram. CONCLUSION: Subtle anomalies, of which echogenic bowel and cl inodactyly are the most significant, further increase Down syndrome sc reening efficiency over standard biometry or the finding of gross anat omic defect. Our data appear to support the addition of subtle anomaly findings to ultrasonographic screening for Down syndrome.