Frontomaxillary facial angle in fetuses with trisomy 21 at 11-13(6) weeks.

OBJECTIVE: The objective of the study was to investigate the location of the front of the maxilla in relation to the forehead in fetuses with trisomy 21 at 11-13 weeks of gestation.

STUDY DESIGN: A three-dimensional volume of the fetal head was obtained before karyotyping in 100 fetuses with trisomy 21 and 300 euploid fetuses. The frontomaxillary facial (FMF) angle, defined as the angle between the upper surface of the upper palate and the frontal bone in a midsagittal view of the fetal face, was measured.

RESULTS: The FMF angle was significantly larger in the trisomy 21 than in the euploid fetuses (mean 88.7 degrees, range 75.4-104 degrees vs mean 78.1 degrees, range 66.6-89.5 degrees, P < .001). The FMF angle was more than 85 degrees in 69% of the trisomy 21 fetuses and in 5% of the euploid fetuses. There was no significant association between the FMF angle and nuchal translucency thickness.

CONCLUSION: Measurement of FMF angle is likely to be a useful adjunct in screening for trisomy 21.