Three-dimensional sonography of prenatal skull base development

To explore longitudinally the development of the fetal skull base using three-dimensional (3D) sonography.

Serial 3D sonographic measurements of anterior skull base length, posterior cranial fossa length and skull base angle were made in 126 normal singleton pregnancies at 18-34 weeks of gestation. In a sub-study of 22 pregnancies, intraobserver variability was determined. Regression analysis for repeated measurements was performed by means of the random coefficients model. Results from an earlier publication on brain volume were extended to the total patient cohort.

Measurements were technically successful in 69-94% of cases. The coefficient of variation for differences between repeated tests within women was 3.5-7.6% and between repeated analyses of the same recorded volume it was 3.0-5.1%. A statistically significant gestational age-related increase was established for both the anterior skull base length and the posterior cranial fossa length and the skull base angle showed a small but significant flexion of about 6 degrees . A higher increment in posterior cranial fossa length relative to anterior skull base angle was established. A significant quadratic relationship could be established for both anterior skull base length (P < 0.0001) and posterior cranial fossa length (P < 0.0001) but not for skull base angle, relative to brain volume.

The reproducibility was acceptable for all fetal skull base measurements. The more pronounced growth in posterior cranial fossa length relative to anterior skull base length is influenced by brain growth. The small flexion of the skull base angle, however, may be caused by other factors. Published by John Wiley & Sons, Ltd.