GROWTH OF THE FETAL FOREHEAD AND NORMATIVE DIMENSIONS DEVELOPED BY 3-DIMENSIONAL ULTRASONOGRAPHIC TECHNOLOGY

Sonographic imaging of the fetal face is important since a number of c hromosomal aberrations are associated with facial malformations. In th e past, imaging of the fetal forehead and diagnosis of frontal bossing had been based on subjective evaluation using two-dimensional ultraso nography. The purpose of this study was to evaluate quantitatively the fetal forehead using three-dimensional technology to generate normati ve data throughout gestation. This should allow the objective diagnosi s of abnormal growth of the fetal forehead, such as frontal bossing. W e also report a case of a fetus with frontal bossing in whom the gener ated nomogram was applied. A cross-sectional study was performed in 13 0 normal healthy singleton pregnancies between 16 and 38 weeks' gestat ion. Using three-dimensional ultrasonography, a line connecting the ap ex of the philtrum and the nasion was drawn across the anterior forehe ad, which delineated the area of the forehead for analysis. The forehe ad length, forehead height, and forehead area under the curve were mea sured and the forehead index was calculated. A second order polynomial growth function was noted throughout gestation for the forehead lengt h (r = 0.93), forehead height (r = 0.97), and forehead area (r = 0.97) . The fetal forehead index remained relatively constant throughout ges tation. The results of this study provide normative data of fetal fore head length, width, and area using three-dimensional ultrasonographic technology. Normative dimensions of the fetal forehead developed and p resented herein are expected to serve as a basis for the objective ass essment of presumed fetal facial abnormalities and may facilitate the detection of the associated syndromes. This is demonstrated in our cas e report of an achondroplastic fetus in whom all forehead dimensions w ere above the 95th percentile.