An objective measurement to diagnose micrognathia on prenatal ultrasound.

Purpose: We introduce the frontal naso-mental angle as an objective measurement for the prenatal detection of fetal retrognathia. The aim of this study is to present normal values for the frontal naso-mental angle from 18 to 35 weeks gestational age.

Materials And Methods: In 81 patients between gestational ages 18 and 35 weeks the frontal naso-mental angle was measured on a profile view of the foetal face. The values were compared with four cases of proven Pierre Robin syndrome.

Results: The frontal naso-mental angle is not dependent on gestational age, the mean value is 146.74 degrees, standard deviation 2.7 degrees; 5th percentile 142 degrees, 95th percentile 151 degrees. All four cases of Pierre Robin syndrome demonstrated a significantly lower frontal naso-mental angle below the 5th percentile.

Conclusion: The frontal naso-mental angle represents an objective way to diagnose retrognathia.