ULTRASOUND EVALUATION OF THE LENGTH OF THE FETAL NASAL BONES THROUGHOUT GESTATION

Subtle facial abnormalities, including smallness of the nose, are comm on findings in trisomy 21 and numerous other genetic conditions. The a im of this study was to construct a normal range for the length of the fetal nasal bones with gestation in a Caucasian population. Ultrasoun d measurements were performed on a strictly mid-sagittal profile in 37 6 normal singleton fetuses at 14-34 (mean 24), weeks' gestation. It wa s found that the length of the nasal bones increased from 4 mm at 14 w eeks to 12 mm at 35 weeks' gestation, and that there was a linear rela tionship between the length of these bones and biparietal diameter and femur length. We conclude that the length of nasal bones can easily b e measured in fetuses at 14-34 weeks' gestation and that such measurem ents might prove useful in the evaluation of pregnancies at high risk for associated fetal abnormalities.