In a total of 618 pregnant women between 9 and 37 weeks' gestation, the fetal face was evaluated by two-dimensional and three-dimensional ultrasound imaging as part of a level III screening evaluation for fetal anomalies. A three-dimensional endovaginal probe (5 MHz) was used for examinations at between 9 and 15 weeks, and an abdominal three-dimensional probe (3.5 MHz) was used after 15 weeks. Three different three-dimensional image display modes were employed: (1) the orthogonal display; (2) the surface display; and (3) the transparent display.
When we studied the three-dimensional orthogonal displays in 125 cases evaluated by abdominal ultrasound, we found that the facial profile shown in the two-dimensional image represented the true mid-sagittal profile in only 69.6% of cases. In the remaining 30.4%, the profile view deviated from a true mid-sagittal section by up to 20° in one or two planes.
In a total of 25 facial anomalies detected by abdominal ultrasound, 20 were clearly demonstrated by both two-dimensional and three-dimensional technology. In the remaining five cases, three-dimensional ultrasound revealed or confirmed an additional defect or abnormality: a narrow cleft lip in an unfavorable position of the fetal face (n = 2), a unilateral orbital hypoplasia (n = 1), a cranial ossification defect (n = 1) and a flat profile in the presence of marked oligohydramnios (n = 1).
When transvaginal scanning was used, there were cases in which a detailed surface image of the fetal face could be obtained as early as 9 weeks' gestation. Abdominal scanning routinely yielded high-quality surface images by 20 weeks. Three-dimensional ultrasound consistently displayed facial abnormalities with greater accuracy and clarity than conventional two-dimensional imaging. This particularly applied to chromosomal aberrations and syndromes associated with subtle facial abnormalities requiring a detailed evaluation.
Not only does three-dimensional ultrasound help in appreciating the severity of a fetal defect, but it can also provide more convincing evidence of a normal fetus than conventional two-dimensional sonograms. Copyright © 1997 International Society of Ultrasound in Obstetrics and Gynecology