Does the combination of fronto-maxillary facial angle and nasal bone evaluation improve the detection of Down syndrome in the second trimester?

Abstract

Objective: To determine if the combination of fronto-maxillary facial (FMF) angle and nasal bone (NB) evaluation improves the detection of Down syndrome (DS) in the second trimester.

Study design: We compared the FMF angle measurements in euploid and DS fetuses seen between 2005 and 2008. The FMF angles were measured from stored two-dimensional (2-D) images by investigators blinded to the DS status of the fetus. All NB measurements were obtained prospectively. Receiver operator characteristic curve plot was used to determine the optimal definition for abnormal FMF angle. The detection and false positive rates and likelihood ratios positive and negative for the DS markers and their combinations were compared.

Results: Of 22 fetuses with DS seen between 16 and 22 weeks over the study period, NB and FMF angle evaluation was available for 21. These were compared with a control group of 201 fetuses seen at similar gestational age ranges without DS. NB alone identified 10/21 (47.6%) of Down syndrome while FMF angle identified 2/21 (9.5%). The combination of FMF angle and NB identified only one additional case of Down syndrome.

Conclusions: While FMF angle and NB are independent markers for DS, their combination resulted in a minimal but nonsignificant improvement in DS detection.