Absent Nasal Bone Helps Predict Down Syndrome

WEDNESDAY, Sept. 17 (HealthDay News) -- While absent nasal bone and increased nuchal folds are both markers for Down syndrome, nasal bone hypoplasia is a more efficient test, according to a report in the September issue of the American Journal of Obstetrics & Gynecology.

Anthony O. Odibo, M.D., of Washington University School of Medicine in St. Louis, and colleagues performed a prospective multicenter cohort study of women undergoing an anatomic survey between 16 and 22 weeks' gestation to compare the efficiency of second-trimester nasal bone hypoplasia to increased nuchal fold for Down syndrome screening. The authors evaluated two definitions of increased nuchal fold (greater than 5 mm and greater than 6 mm) and compared fetuses or infants with Down syndrome to those fetuses without Down syndrome for the presence of nasal bone hypoplasia and increased nuchal fold.

Overall, 50 Down syndrome cases occurred among the 4,373 pregnancies evaluated over a five-year period, the report indicates. Nasal bone hypoplasia and nuchal fold evaluations were obtained in 90 percent and 100 percent of pregnancies, respectively. Nasal bone hypoplasia was seen in 29 percent of cases (14/49), and an increased nuchal fold of greater than 6 mm was seen in 12 percent of cases (6/50) with Down syndrome.

"Nasal bone and nuchal fold are efficient markers for Down syndrome," the authors conclude. "Absent nasal bone was a better predictor of Down syndrome, compared with nuchal fold, and should be a standard marker when a second-trimester genetic sonogram is performed."

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