Absent or shortened nasal bone length and the detection of Down Syndrome in second-trimester fetuses.

OBJECTIVE: To estimate the accuracy of evaluating nasal bone length, expressed as multiples of the median (MoM), for the detection of Down syndrome in second- trimester fetuses. METHODS: Expected normal median nasal bone measurements were established for an initial cohort of women receiving fetal ultrasound examinations at 15-24 weeks of gestation. Nasal bone lengths were converted to MoM with adjustment for maternal race and ethnicity using whites as the referent group. Nasal bone MoM were compared in euploid and Down syndrome fetuses. The sensitivity and specificity were evaluated in this initial cohort and in a second cohort in which all ultrasound measurements were carried out prospectively. RESULTS: For the combined data set, 10 of 21 affected pregnancies had an absence of the nasal bone (sensitivity 47.6%), but absence was noted in only 1 of 2,515 unaffected pregnancies (false-positive rate 0.04%). Using less than 0.80 MoM as a cutoff, the sensitivity was 20 of 21 (95.2%), and the false-positive rate was 185 of 2,515 (7.4%). Changing the cutoff to 0.75 MoM resulted in 18 of 21 (85.7%) sensitivity and 74 of 2,515 (2.9%) false-positive rate. Using medians derived from whites to calculate MoM for the entire population resulted in higher false-positive rates. CONCLUSION: Nasal bone length expressed as MoM seems to be an useful ultrasound marker for Down syndrome in second-trimester fetuses with a high sensitivity and a low false-positive rate. LEVEL OF EVIDENCE: III.

Use of the mitral valve-tricuspid valve distance as a marker of fetal endocardial cushion defects.

OBJECTIVE: The purpose of this study was to compare the mitral valve-tricuspid valve distance in second-trimester fetuses with normal cardiac anatomy versus those fetuses with endocardial cushion defects. STUDY DESIGN: We identified fetuses between 16 and 24 weeks of gestation. The distance between the insertions of the medial leaflets of the mitral and tricuspid valves were obtained. Linear regression curves were generated. RESULTS: The mean mitral valve-tricuspid valve distance for 86 fetuses with normal cardiac anatomy was 2.02 mm, compared with 0.37 mm in 13 fetuses with endocardial cushion defects ( P = .0001). Linear regression curve correlating mitral valve-tricuspid valve distance with gestational age showed a gradual slope (R 2 = 0.28; P < .0001). With a mitral valve-tricuspid valve distance < 5th percentile as a marker for the diagnosis of endocardial cushion defect gave a sensitivity of 69.2%, a specificity of 100%, a positive predictive value of 100%, a negative predictive value of 95.6%, and a false-positive rate of 0% ( P = .0001). CONCLUSION: The mitral valve-tricuspid valve distance is useful clinically in the detection of endocardial cushion defects in second-trimester fetuses.