Maternal Mortality Underreporting in Brazil Due to Coding Errors (2010-2021).

Accurate maternal death tracking is a global priority to guide resource allocation for reduction of preventable maternal mortality. This retrospective observational study evaluated the accuracy of the Brazilian maternal death coding system and compared the official maternal mortality ratio (MMR) with a recalculated MMR including any reclassified maternal deaths. Mortality data from 2010 to 2021 were analyzed, including officially reported maternal deaths and deaths of women aged 10-49 years with pregnancy-puerperal status indicated on their death certificate but not coded as maternal. Brazil recorded 21,670 official and 3,480 uncoded maternal deaths during the study period. Inclusion of reclassified maternal deaths increased the median MMR from 58.2 to 67.5 per 100,000 live births. Uncoded maternal deaths compared with coded deaths were more likely among those with lower education, at younger and older maternal ages, with indirect causes of death, and with fewer death investigations. Improved maternal death coding is essential to reduce maternal mortality underreporting.