The vertebral canal reaches maturity early in life. The size of the lumbar spinal canal was evaluated to determine normal values for vertebral canal size.

For our prospective cross-sectional study 95 women with a singleton pregnancy between 16 and 41 weeks of gestation were recruited during their routine anomaly scan. After defining the region of interest on the 2D ultrasound image, volume scanning was performed and the rendered volume was displayed in three orthogonal planes on the screen. Area and volume of the vertebral canal in L1, L3 and L5 were calculated.

Area and volume of the vertebral canal showed a close correlation to gestational age. Advancing gestational age was characterised by a statistically significant increase in all volumetric and conventional 2D measurements. No major differences regarding area and volume measurements could be found between upper and lower spine.

Sonographic evaluation of the fetal spine plays an important role in obstetric anomaly scans. Prenatal diagnosis may also lead to interesting aspects concerning back pain in adults. A small vertebral canal is considered to be one of the causes for back pain in later life but these syndromes are multi-factorial. Since interpedicular diameter of the spinal canal at the level of L1-L4 at birth is approximately 70 % of the adult size, any kind of intrauterine growth impairment will affect further development. Further data will show if our normal values will have significance in the early detection of disorders of the vertebral canal.