Growth of the fetal forehead and normative dimensions developed by three-dimensional ultrasonographic technology

Sonographic imaging of the fetal face is important since a number of chromosomal aberrations are associated with facial malformations. In the past, imaging of the fetal forehead and diagnosis of frontal bossing had been based on subjective evaluation using two-dimensional ultrasonography. The purpose of this study was to evaluate quantitatively the fetal forehead using three-dimensional technology to generate normative data throughout gestation. This should allow the objective diagnosis of abnormal growth of the fetal forehead, such as frontal bossing. We also report a case of a fetus with frontal bossing in whom the generated nomogram was applied. A cross-sectional study was performed in 130 normal healthy singleton pregnancies between 16 and 38 weeks' gestation. Using three-dimensional ultrasonography, a line connecting the apex of the philtrum and the nasion was drawn across the anterior forehead, which delineated the area of the forehead for analysis. The forehead length, forehead height, and forehead area under the curve were measured and the forehead index was calculated. A second order polynomial growth function was noted throughout gestation for the forehead length (r = 0.93), forehead height (r = 0.97), and forehead area (r = 0.97). The fetal forehead index remained relatively constant throughout gestation. The results of this study provide normative data of fetal forehead length, width, and area using three-dimensional ultrasonographic technology. Normative dimensions of the fetal forehead developed and presented herein are expected to serve as a basis for the objective assessment of presumed fetal facial abnormalities and may facilitate the detection of the associated syndromes. This is demonstrated in our case report of an achondroplastic fetus in whom all forehead dimensions were above the 95th percentile.