The morphology of the vertebral venous plexus (Figs. 27.1, 27.2, 27.3 and 27.4) is believed to vary with age. In 2005, Groen et al. conducted a study on human fetuses between 21 and 25 weeks gestational age. The findings confirmed previous studies showing that the posterior intravertebral venous plexus lacked transverse bridging veins in the fetus, in contrast to a mature sample. This is suspected to be a result of developmental delay, or simply a difference between prenatal and postnatal life (Groen et al. 2005).