Why Aren’t There More Maternal Deaths? A Decomposition Analysis

John A. Ross of the Futures Group and MHTF Director Ann K. Blanc recently published a decomposition analysis of maternal deaths based on data published last year by the UN and Hogan et al. The paper notes that despite an increase in female populations of 42% during the period between 1990 and 2008, the number of maternal deaths actually declined. Ross and Blanc analyze the three components (women of reproductive age; general fertility rate; and maternal mortality ratio) that are used to calculate the number of maternal deaths in order to help explain the decline:

For the developing world as a whole, and for the two major regions that account for most deaths, we follow the 1990–2008 trends to obtain the relative change in each of the three determinants. The purpose is to quantify the role of the three components in determining the number of deaths. Since the number of maternal deaths is simply the product of the number of women, the GFR, and the MMR, the effect of each can be obtained by holding the 1990 value constant to 2008 and noting the difference from the actual trend. That, together with the ratios of change, provides a picture of the role of each of the three determinants.

Additionally, they ran a similar analysis for the maternal death rate, which is the number of deaths per 1,000 women aged 15-49 per year. Ross and Blanc conclude:

The average woman’s annual risk of a maternal death, the maternal death rate, fell by over half in the 18-year period examined here. Without the past decline in fertility of nearly one-third, and the decline in the MMR of over a third, the numbers of maternal deaths would have been about 44% higher, with 3.6 million more deaths between 1990 and 2008.

The decline in annual deaths from 541,000 in 1990–355,000 in 2008 has been achieved despite the growth in numbers of women. The particular contribution of the fertility decline has been to keep the absolute number of births constant; that has been overlooked in the literature of the field, but the effect is of the same magnitude as that of the decline in the MMR. There has also been an interaction between the two effects, first by averting many births on which the MMR would otherwise have acted, and second because greater contraceptive use has also helped lower the average MMR by improving the mix of births according to their risk profiles, shifting births away from high parities and older ages of mothers.