Country estimates of maternal mortality: an alternative model

Ever since the publication of country level estimates of maternal mortality for 1990 by WHO and UNICEF, there has been some degree of controversy about these estimates. The recent publication of a 1995 revision, based on the modification of the multivariate model used for 1990, has not managed to put this controversy to rest. Countries with national estimates of their own have generally protested against the higher figures resulting from the multivariate modelling approach used by WHO and UNICEF, but some experts have also objected to the model itself. As a result of earlier discussions with the WHO/UNICEF team, some adjustments were incorporated into their model, notably the age standardization of maternal mortality ratios (MMRs) and proportions maternal among deaths of females of reproductive age (PMDF) of demographic and health surveys (DHS) direct sisterhood data, as the use of unstandardized values was shown to cause systematic biases. However, a model feature that continued to be controversial was the use of the PMDF as the dependent variable. As will be shown in this paper, the use of this dependent variable has a number of conceptual and practical disadvantages, such as its dependence on non-maternal deaths and the need for separate projections of births and deaths of women of reproductive age, in order to convert the estimated PMDF into a more conventional MMR. The latter greatly increases the uncertainty of the resulting MMR estimates, even though this additional variance is ignored in the WHO/UNICEF estimates of confidence intervals. On balance, the MMR, while also subject to some legitimate objections, is still considered preferable as an independent variable. This paper therefore derives alternative country estimates for 1995 based on a multivariate model of the MMR. The model is shown to lead to smaller root mean square relative errors of the MMR estimates. While the overall number of maternal deaths estimated worldwide is very similar to the number reached by WHO/UNICEF, there are major disagreements with respect to particular countries. Finally, a discussion is included on the appropriate way to incorporate the DHS direct sisterhood data, as this affects the results substantially.