5.3 ESTIMATION OF MATERNAL AND INFANT MORTALITY INDICATORS
Given the need to establish a baseline for measuring progress toward Millennium Development Goal 5 (MDG-5, and now SDG-3), and the lack of reliable data on global trends in maternal mortality, it was necessary to estimate the number of maternal deaths, as well as the maternal mortality ratio (MMR).
Many countries have made important advances in detecting and recording maternal deaths and live births; they therefore have reliable, though still imperfect, data. At the same time, measuring maternal mortality continues to pose a major challenge. In 2013, according to data reported to PAHO from Member Countries, the absolute number of maternal deaths for Latin America and the Caribbean was around 6,000 per year. The actual number is probably greater, since some countries with relatively high absolute numbers of maternal deaths (Bolivia, Guyana, Haiti, and Trinidad and Tobago) did not report data. However, for the same period, the Maternal Mortality Estimation Inter-agency Group (MMEIG), which includes WHO, UNICEF, UNFPA, and the World Bank, estimated approximately 9,300 maternal deaths, while the Institute for Health Metrics and Evaluation (IHME) estimated 7,600. These three different figures create considerable consternation among the reporting countries. Although there are some similarities among the methodologies used by various groups for estimating trends in maternal mortality, the causes of the major differences merit explanation.Due to the importance of these indicators, two methodologies that can be used to measure the accuracy of the maternal mortality ratio and of infant mortality rates calculated with country-level sources will be discussed.
5.3.1 METHODOLOGY USED BY THE MATERNAL MORTALITY ESTIMATION INTER-AGENCY GROUP (MMEIG)
The United Nations MMEIG divides countries into three groups, A, B, and C. However, the countries in the Region of the Americas are in groups A and B. Group A is composed of countries with good vital registration data. Using the MMEIG methodology, the number of maternal deaths reported by a country is multiplied by a correction factor of 1.5 to correct for misclassifications except in cases where the country corrects its own information with national data from a published study on the proportion of underreported and poorly classified cases. The 1.5 correction factor stems from two studies by Lewis London: Confidential Enquiry into Maternal and Child Health (2004 and 2007).
The countries in Group B lack complete vital registration data but they use other types of data sources. For these countries, the MMEIG methodology estimates the maternal mortality ratio using a model with three predictive factors as measures of exposure to risk. These factors are:
- Per capita gross domestic product
- Proportion of live births attended by skilled personnel
- Overall fertility rate (live births per woman in the 15 to 49 year age group).
The proportion obtained is used to estimate the total number of deaths of women of childbearing age which is then divided by the total number of births to estimate the maternal mortality ratio. These two data items are drawn from United Nations Statistical Division (UNSD).
5.3.2 THE METHO DOLOGY USED BY THE INSTITUTE FOR HEALTH METRICS AND EVALUATION (IHME)
The model used by the Institute for Health Metrics and Evaluation (IHME) does not take account of variations in the quality of information from the countries, and thus the methodology is applied to all of the countries without distinction. The predictive variables used are:
- Per capita gross domestic product
- Educational level of women, differentiated by age
- Neonatal mortality rate
- Total fertility rate
- Prevalence of HIV/AIDS (this variable represents a difference from the model used by the MMEIG, which does not consider this variable; thus, an estimate of mortality due to this cause is first performed, and the estimate is then corrected).
The IHME corrects problems of under-enumeration and poor quality records by multiplying by a correction factor of 1.4.
5.3.3 ESTIMATES OF INFANT MORTALITY IN THE REGION OF THE AMERICAS
Assessment of achievements with regard to Millennium Development Goal 4 (MDG-4) was based on analysis of under-5 mortality. However, given the differences in mortality risk and in the cause-based structure of mortality during the first years of life, analysis that permits such disaggregation is essential for analyzing the impact of specific interventions and planning future actions.
The available information comes from different sources and methodologies, whose differences need to be assessed when interpreting the data. PAHO consolidates and presents data based on the countries' mortality reports. Annual birth figures are derived from estimates made by the United Nations Population Division and by the United States Census Bureau. Infant mortality and under-5 mortality rates are based on these data sources.
At the global level, estimates are provided by the U.N. Inter-agency Group for Child Mortality Estimation (IGME), as well as by the IHME. The methodological approaches of these two sources differ with regard to the basic data, their processing, and the adjustment processes employed. The most important discrepancies in the results are attributable to changes in mortality in the countries, the corrections or adjustments applied, and the models used to obtain the estimates in response to problems in coverage of vital statistics.
As with other data sources, the usefulness of mortality statistics, as well as the accuracy of the data, depends largely on their quality, which is associated primarily with above the degree of coverage.
The mid-term evaluation of the Regional Plan for Neonatal Health included an analysis of the coverage and accuracy of information on neonatal deaths obtained from vital statistics systems. The evaluation was done using information from the databases available to the PAHO Health Information and Analysis team. The databases included information on neonatal, infant, and child deaths for 47 countries in the Region between 1995 and 2010. These databases generated indicators of neonatal, infant, and child mortality, which were compared with direct estimates based on DHS/RHS and WHO (WHOSIS) surveys, as well as with indirect estimates of the IGME, IHME, and UNICEF (MICS surveys). Similarly, the PAHO databases were used to obtain the distribution of neonatal, infant, and child deaths by causes. In this case, direct estimation was complemented by the compilation of measures produced by the Child Health Epidemiology Reference Group (CHERG).
Based on the analyses, coverage of total deaths was determined to be good in 21 countries, satisfactory in six, and fair to deficient in 12. Thus, the average level of coverage of total deaths is high (median 94%). The consistency of the estimates is generally comparable with the data provided by UNSD for years close to the years analyzed, both with regard to the countries as a whole (median 93.5%), and to the majority of countries individually.
There is an inverse relationship between the percentage of coverage of deaths and the relative difference between the rates obtained by direct and indirect methodologies (the higher the former, the lower the latter). With regard to infant and child mortality, the correlations between the percentage of coverage and the relative difference between direct and indirectly estimated rates was greater than the indirect estimates calculated by the IHME. In the case of neonatal mortality, the association was higher in terms of the relationship between percentage of coverage and the relative difference between the direct rates and those calculated by the IGME.
It is also evident that the causes cited on declarations of death in the Region's countries are accurate to an acceptable degree, with the frequencies of ill-defined causes being less than 10%. Thus, although the quality of mortality information in the Region needs to be improved, levels of both coverage and precision are generally adequate. The better such measurements are, the greater will be the benefit of information based on direct, versus indirect, sources.