We welcome the study by Margaret Hogan and colleagues,1 which provides important new estimates for maternal mortality rates (MMR) in 181 countries. However, we would have liked to see additional discussion on the presentation of the individual-level data.
As a specific example, from our work in Malawi and analysis of the Demographic and Health Survey (DHS) data on maternal mortality (unpublished), the graph for Malawi seems to overestimate MMR. The last two sibling history data points (which we assume are for the DHS 2000 and 2004 surveys) are higher than the published estimates of 1120 (2000)2 and 984 (2004).3 Although these two points are correctly centred around 1997 and 2001, respectively, reflecting the retrospective nature of the sisterhood method, the rates are around 1400 and 1500, respectively, which seems high even after accounting for upward adjustment based on the analyses of Obermeyer and colleagues.4
We presume that the upward adjustments are based on Gakidou-King weights, which correct for families with high mortality being under-represented, and then an additional upward adjustment which represents the fact that deaths are less likely to be reported the longer ago they occurred. Obermeyer and colleagues report that on average the Gakidou-King weights will increase adult mortality rates upwards by 27%. The upward adjustment for Malawi was of the order of 40%. In the case of Mali, where the DHS 2006 gives an MMR of 464 but is plotted at about 800 in the paper, the upward adjustment is even more significant.
Given the scale of some of these adjustments, we believe that some discussion of these changes was necessary, and that the plots should have been labelled as “adjusted sibling history” to avoid potential for confusion.