Maternal Aboriginality is under-reported on the MDC. One method of assessing the extent of under-reporting and monitoring improvements over time is to compare the reporting on maternal Aboriginality as reported to the MDC with information on birth registrations reported to the NSW Registry of Births, Deaths and Marriages. Using capture-recapture methods, an estimate of the total number of Aboriginal mothers can be obtained and compared with the number of Aboriginal mothers reported to the MDC. The method used here is described in Chapter 3 (page 13).