ArticlesEstimates of maternal mortality worldwide between 1990 and 2005: an assessment of available data
Introduction
Maternal mortality—ie, the death of a woman during pregnancy or in the 42 days post partum due to causes directly or indirectly associated with the pregnancy—has been a priority area for the global health and development community at least since the Nairobi Safe Motherhood Conference in 1987. That conference, attended by representatives from 50 developing countries and from key development agencies, has been followed by numerous international forums at which safe motherhood was on the agenda. The 2000 Millennium Summit established the improvement of maternal health as Millennium Development Goal (MDG) 5.1 The target of MDG5 is to reduce the maternal mortality ratio (defined as maternal deaths in a time period, usually 1 year, divided by the number of livebirths in the same period, and conventionally expressed per 100 000 livebirths) by 75% between 1990 and 2015; for a country to achieve this target requires an average decrease of 5·5% per year in the maternal mortality ratio.
Country estimates of maternal mortality are essential to inform national decisionmaking and resource allocation, to underpin advocacy efforts, and to stimulate research. Additionally, international development partners and donors rely on sound estimates to inform their own decisionmaking on resource allocation. Yet currently available country data vary greatly in quantity and quality and do not readily lend themselves to comparisons, either over time or between countries. The best way of reliably measuring maternal mortality is through a civil registration system that registers all deaths and provides medical certification of cause of death. However, even where such systems exist, vigilance is necessary to ensure that all maternal deaths are correctly classified; studies have shown maternal deaths to be under-reported.2, 3, 4, 5, 6 In countries lacking complete recording of adult deaths—eg, most low-income countries—alternative approaches are needed. Researchers have developed a range of alternative measurement strategies and data availability has increased over the past 15 years. Yet in countries representing a quarter of global births there remains little empirical basis for estimating maternal mortality.
UNICEF, WHO, and the UN Population Fund (UNFPA) have previously developed global, regional, and country estimates of maternal mortality for the years 1990, 1995, and 2000.7, 8, 9 In 2006 a new maternal mortality working group was established that included WHO, UNICEF, UNFPA, the UN Population Division, and the World Bank, as well as several outside technical experts, to develop new estimates of maternal mortality for 2005. As a starting point, this group reviewed a set of suggested improvements, prepared as part of an external review commissioned by WHO, to the methods that had been used for the 2000 estimates. In response to these suggestions and to questions posed by countries after the 2000 round of estimates, the working group agreed on ways to classify countries on the basis of data availability, on how to adjust data derived from different sources to enhance comparability across countries and across time, and on the specifications for the statistical model used to predict values for countries lacking appropriate data. Here, we describe the new methods used and present national, regional, and global 2005 estimates of maternal mortality. We also address the challenge of comparability of estimates over time and generate some broad conclusions about global and regional trends since 1990.
Section snippets
Methods
Our unit of analysis was the country. Countries have used a range of different data collection approaches to generate estimates of maternal mortality. Our analysis was restricted to nationally representative sources of data. Sources were identified in collaboration with countries through WHO, UNICEF, and UNFPA country representatives as well as from internationally coordinated survey programmes; our cutoff for the review of data sources was March, 2007. Different data sources require different
Results
We estimate that there were about 535 900 maternal deaths worldwide in 2005, and the maternal mortality ratio was about 402 maternal deaths per 100 000 livebirths (table 1). Most maternal deaths were concentrated in sub-Saharan Africa (270 500, 50% of deaths worldwide) and Asia (240 600, 45% of deaths worldwide); almost half (48%) of maternal deaths worldwide in 2005 was concentrated in just five countries: India (117 100), Nigeria (58 800), the Democratic Republic of Congo (32 300),
Discussion
Our results indicate that the worldwide maternal mortality ratio for 2005 is about 402 deaths per 100 000 livebirths, which represents about 535 900 maternal deaths in 2005. At the national level, estimated maternal mortality ratios range from below 10 deaths per 100 000 livebirths in most developed countries to as high as 2000 deaths per 100 000 livebirths in some developing countries. This huge difference in risk dwarfs differences for other commonly used health indicators, such as the infant
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