Absent nasal bone better than nuchal fold for Down syndrome screening

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 and Gynecology.

Anthony O. Odibo, MD, 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 (> 5 mm and > 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% and 100% of pregnancies, respectively. Nasal bone hypoplasia was seen in 29% of cases (14/49), and an increased nuchal fold of greater than 6 mm was seen in 12% of cases (6/50) with Down syndrome.

Odibo AO, Sehdev HM, Gerkowicz S, et al. Comparison of the efficiency of second-trimester nasal bone hypoplasia and increased nuchal fold in Down syndrome screening. Am J Obstet Gynecol. 2008;199:281.e1-281.e5.