Statistics on maternal mortality are produced based on the database of causes of death. "Maternal deaths" are selected from the database via a complex procedure, which takes into account the definition given by the WHO and is described in detail in the metadata. The tenth revision of the International Classification of Diseases (ICD-10) defines maternal death as "the death of a woman while pregnant or within 42 days of termination of pregnancy, irrespective of the duration and the site of the pregnancy, from any cause related to or aggravated by the pregnancy or its management, but not from accidental or incidental causes." "Maternal deaths should be subdivided into two groups. Direct obstetric deaths: those resulting from obstetric complications of the pregnant state (pregnancy, labour and puerperium), from interventions, omissions, incorrect treatment, or from a chain of events resulting from any of the above. Indirect obstetric deaths: those resulting from previous existing disease or disease that developed during pregnancy and which was not due to direct obstetric causes, but which was aggravated by physiologic effects of pregnancy." Furthermore, the ICD-10 also defines late maternal death as "the death of a woman from direct or indirect obstetric causes more than 42 days but less than one year after termination of pregnancy." The "maternal mortality rate" is the ratio between the number of recorded direct and indirect maternal deaths over one year and the number of live birth in the same year, expressed per 100,000 live births. Late maternal deaths are not taken into account in the calculation of this ratio. Given the small and markedly variable number of cases recorded each year in Belgium, it has been decided to calculate this ratio based on the cumulated maternal deaths and live births of five consecutive years, with the ratio calculated being recorded in the middle year. When identifying these maternal deaths, the ad hoc working group, bringing together the Belgian statistical office and all data producing federated entities, did not exclude the risk of an underestimation of these deaths, based on the only statistical bulletin used as main source. It therefore asks for continued efforts to further improve the follow-up of maternal deaths, and supports the recent initiative of the College of physicians for Mother and Newborn to consider the creation of a maternal mortality register.