The fetal spinal canal--a three-dimensional study.

The size of the lumbar spinal canal was evaluated in a prospective cross-sectional ultrasound (US) study to determine normal size values for lumbar part of the vertebral canal. A total of 88 patients undergoing routine obstetric US were studied between 16-41 weeks gestation. Structural anomalies or growth restriction were excluded. Area and volume of the vertebral canal in L1, L3 and L5 were calculated by three-dimensional (3-D) US. The size of the spinal canal correlated well with gestational age and no major differences could be found between upper and lower lumbar spine. By 3-D US, in vivo assessment of the spinal canal becomes possible. Further studies are needed to confirm our findings.