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.


CONCLUSIONS
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.


METHODS
III.
Gianferrari
Elisa A
EA
Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Connecticut Health Center, 114 Woodland Street, Farmington, CT 06105, USA.
Benn
Peter A
PA
Dries
Lisa
L
Brault
Kim
K
Egan
James F X
JF
Zelop
Carolyn M
CM
D000328:Adult; D016022:Case-Control Studies; D015331:Cohort Studies; D004314:Down Syndrome / Q000000981:diagnostic imaging* / Q000208:ethnology / Q000473:pathology*; D005006:Ethnicity; D005260:Female; D005865:Gestational Age; D006801:Humans; D009295:Nasal Bone / Q000000981:diagnostic imaging* / Q000473:pathology*; D011237:Predictive Value of Tests; D011247:Pregnancy; D016216:Ultrasonography, Prenatal; D044465:White People