Three-dimensional sonographic determination of normal fetal mandibular and maxillary size during the second half of pregnancy

Abstract

Objective: To explore the various ways of obtaining fetal maxillary and mandibular size with three-dimensional (3D) ultrasound, with a view to developing a tool for identifying minor anomalies in the lower facial region.

Methods: Serial 3D sonographic measurements of the fetal jaws were made in 126 normal singleton pregnancies at 18-34 weeks of gestation for determination of degree of maxillary and mandibular protrusion, maxillary and mandibular corpus lengths, mid- and lower facial depths and maxillary and mandibular curvature. In a sub study the reproducibility of the measurements was evaluated.

Results: The coefficient of variation in the reproducibility study varied between 7.1 and 10.5%. For all parameters except maxillary and mandibular protrusion, there was a significant gestational age-related increase. Ratios of maxillary/mandibular protrusion, maxillary/mandibular corpus lengths, mid-/lower facial depths and maxillary/mandibular curvature all showed a significant gestational age-related decrease, with the most distinct decrease in the mid-/lower facial depth ratio.

Conclusions: 3D sonographic measurement of the fetal maxilla and mandible demonstrated an acceptable intraobserver variability for all measurements. The mid-/lower facial depth ratio appears to be most valuable in determining abnormal mandibular development.