First trimester supratentorial and infratentorial abnormalities in fetuses with open spina bifida.

Objectives: To examine whether supratentorial, infratentorial, and calvarial manifestations of open spina bifida (OSB) occur in the first-trimester.

Methods: Supratentorial (midbrain curvature, thalamic height), infratentorial (fourth ventricle diameter, brain-stem diameter [BSD], ratio of BSD to BSD-occipital bone diameter [BSOB]), and calvarial (frontomaxillary facial [FMF] angle) parameters were measured in stored midsagittal facial images at 110-136 weeks of 500 normal and 10 open spina-bifida fetuses by 3 blinded examiners.

Results: OSB fetuses displayed a larger midbrain curvature (93.