Objective: The objective of the study was to investigate the potential value of the frontomaxillary facial (FMF) angle in second-trimester ultrasound screening for trisomy 21.
Methods: We examined stored images of fetal profiles taken before amniocentesis at 14-24 weeks from 100 euploid fetuses and 34 with trisomy 21. The FMF angles between the upper surface of the upper palate and the frontal bone (FMF(bone)) and the skin over the forehead (FMF(skin)) were measured.
Results: In the euploid group the FMF angles decreased with gestation. In the fetuses with trisomy 21, the FMF(bone) and FMF(skin) angles were 79.4% and 87.9% above the 95th percentile for gestation of the respective values from the euploid group. In trisomy 21 fetuses, there was no significant difference in FMF angles between those with nasal bone hypoplasia (n = 19) and those without (n = 15).
Conclusion: The FMF angle is substantially higher in trisomy 21 than euploid fetuses. Measurement of the FMF angles is likely to prove a useful method in prenatal screening for trisomy 21 in the second trimester.