Antenatal factors in the development of the lumbar vertebral canal: A magnetic resonance imaging study

The lumbar vertebral canal was measured in two cohorts of 10-year-old children (n = 161) using magnetic resonance imaging (MRI) and compared with obstetric records. To investigate whether there are identifiable obstetric factors that determine the size of the lumbar vertebral canal. The most rapid period growth for the lumbar vertebral canal is between 12 and 32 weeks in utero, with the midsagittal diameter of L1-L4 already 70% of adult dimension at birth. Therefore, adverse antenatal factors during this critical growth period may be expected to affect the size of the canal. The canal size was measured from axial MRI sections taken through each lumbar vertebra (L1-L5) at the pedicular level of 84 children. Relations with obstetric data, prospectively collected in a neonatal database, were sought. The relation of low birthweight and canal size was further investigated in a second cohort of children (n = 77). The canal size, particularly the midsagittal diameter and the cross-sectional area, was found to be significantly reduced by low birthweight (with growth retardation in utero being a more important factor than length of gestation), low placenta weight, and lower socioeconomic class. Smoking during pregnancy significantly reduced the perimeter at L3 (P = 0.032) and L5 (P = 0.031), and also the cross-sectional area at L3 (P = 0.030) and L5 (P = 0.016). This study showed that, for this group of children, the size of the lumbar vertebral canal was reduced by low birthweight, with maternal smoking as an added adverse factor. Therefore, good antenatal care and maternal education may help to reduce the risk of spinal stenosis in adult life.