The luminosity system is an integral part of the DO detector that must be properly maintained to provide accurate luminosity measurements for physics analysis. After the addition of a readout layer to the silicon vertex detector in 2006, it was necessary to re-calculate the effective inelastic cross section to which the luminosity monitor is sensitive. The preliminary analysis showed that the luminosity constant did not change with the addition of the extra layer of silicon. A full study of the revised luminosity constant including a complete analysis of systematic uncertainties has been completed. The luminosity constant was determined to be sigmaeff = 48.3 +/- 1.9 +/- 0.6 mb, which reduces the DO contribution to the luminosity measurement uncertainty by almost 3%.