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5.1 Maternal mortality ratio

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Modified on 2012/03/05 16:07 by MDG Wiki Handbook Categorized as Goal 5
Contents

GOAL AND TARGET ADDRESSED

Goal 5. Improve maternal health
Target 5.A: Reduce by three quarters, between 1990 and 2015, the maternal mortality ratio

DEFINITION AND METHOD OF COMPUTATION

Definition
The maternal mortality ratio (MMR) is the annual number of maternal deaths from any cause related to or aggravated by pregnancy or its management (excluding accidental or incidental causes) during pregnancy and childbirth or within 42 days of termination of pregnancy, irrespective of the duration and site of the pregnancy, per 100,000 live births, for a specified year.

Concepts
Maternal deaths can be divided into two groups, namely direct and indirect obstetric deaths. Direct obstetric deaths result from obstetric complications of the pregnant state (pregnancy, labour and puerperium); from interventions, omissions or direct treatment; or from a chain of events resulting from any of these. Indirect deaths result from previously existing diseases, or diseases that developed during pregnancy, which were not directly due to obstetric causes, but were aggravated by the physiological effects of pregnancy.

A live birth is the complete expulsion or extraction from its mother of a product of conception, irrespective of the duration of the pregnancy, which, after such separation, breathes or shows any other evidence of life—such as beating of the heart, pulsation of the umbilical cord, or definite movement of voluntary muscles—whether or not the umbilical cord has been cut or the placenta is attached. Each product of such a birth is considered a live birth.

Method of computation
The maternal mortality ratio is calculated by dividing recorded (or estimated) maternal deaths by total recorded (or estimated) live births in the same period and multiplying by 100,000. The measurement requires information on pregnancy status, timing of death (during pregnancy, during childbirth, or within 42 days of termination of pregnancy), and cause of death.

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RATIONALE AND INTERPRETATION

This indicator monitors deaths related to pregnancy and childbirth. It reflects the capacity of health systems to provide effective health care in preventing and addressing the complications occurring during pregnancy and childbirth.

Indicator values range from less than 10, as in most developed countries, to over 1,000, with an average of around 290 per 100,000 live births in the developing regions. Values above 1,000 however are found in a relatively small group of countries and are to be considered extremely high. According to international estimates, in 2008, 14 countries had maternal mortality ratios of or above 1,000.

Estimating maternal mortality, in particular when there are problems with data quality, results in wide ranges of uncertainty bracketing the produced estimates. It is therefore, advisable to interpret the maternal mortality ratio within the context of other reproductive health-related information including presence of skilled health personnel at delivery, antenatal care, and levels of fertility.

SOURCES AND DATA COLLECTION

Primary sources of data include vital registration systems, household surveys, reproductive age mortality studies, disease surveillance or sample registration systems, special studies on maternal mortality, and national population censuses. Complete vital statistics registration systems with accurate cause of death estimations are the most reliable data source for calculating maternal mortality and monitoring change over time. However, these are rare in developing countries. Official data are usually available from health service records, but few women in rural areas have access to health services. Therefore in developing countries, survey data, especially those from the Demographic and Health Surveys (DHS) and similar household surveys constitute the most common source of data on maternal mortality.

Because maternal mortality is a relatively rare event, large sample sizes are needed when data are derived from household surveys. This is very costly and may still result in estimates with large confidence intervals.

The sisterhood method, used in DHS surveys, reduces sample size requirements by asking survey respondents about the survivorship of sisters. Respondents are asked four simple questions about how many of their sisters reached adulthood, how many have died and whether those who died were pregnant at the time of death. While this method reduces sample size requirements, it produces estimates covering some 7-12 years before the survey, which renders data problematic for monitoring progress or observing the impact of interventions. The direct sisterhood method asks respondents to provide date of death, which permits the calculation of more recent estimates, but even then the reference period tends to refer to 0-6 years before the survey.

DISAGGREGATION

Due to the large margins of uncertainty surrounding these estimates, maternal mortality ratios are presented at the national level only. Disaggregation is not recommended.

COMMENTS AND LIMITATIONS

Maternal mortality is difficult to measure. Vital registration and health information systems in most developing countries are weak, and thus, cannot provide an accurate assessment of maternal mortality. Even figures derived from complete vital registration systems, such as those in developed countries, suffer from misclassification and underreporting of maternal deaths.

Due to very large confidence intervals, maternal mortality estimates might not be suitable for assessing trends over time. As a result, it is recommended that country level process indicators, such as attendance by skilled health personnel at delivery and use of health facilities for delivery, be used to supplement maternal mortality ratios for assessing progress towards the reduction in maternal mortality at the country level.

The maternal mortality ratio should not be confused with the maternal mortality rate (whose denominator is the number of women of reproductive age), which reflects not only the risk of maternal death per pregnancy or birth but also the level of fertility in the population. The maternal mortality ratio (whose denominator is the number of live births) indicates the risk of death once a woman becomes pregnant, and does not take fertility levels into consideration.

GENDER EQUALITY ISSUES

The low social and economic status of girls and women is a fundamental determinant of maternal mortality in many countries. Low status limits the access of girls and women to education, good nutrition and family planning—key determinants of too early, too many, and risky pregnancies—as well as to the necessary health services to prevent and/or treat complications of pregnancy and childbirth.

DATA FOR GLOBAL AND REGIONAL MONITORING



Maternal mortality ratios can be calculated directly from data collected through vital registration systems, household surveys or other sources. However, these sources might have data quality problems, particularly related to the underreporting and misclassification of maternal deaths, and they may have limited comparability.

The World Health Organization (WHO), United Nations Children’s Fund (UNICEF), United Nations Population Fund (UNFPA) and The World Bank (WB) have developed a method of adjusting existing data in order to take into account these data quality issues and to ensure the comparability of different data sources. This method involves assessing data for completeness and, where necessary, adjusting for underreporting and misclassification of deaths as well as development of estimates through statistical modelling for countries with no reliable national level data.

Data on maternal mortality and other relevant variables are obtained through databases maintained by WHO, the United Nations Population Division, UNICEF, and WB. Data from countries varies in terms of the source and methods. Given the variability of the sources of data, different methods are used for each data source in order to arrive at country estimates that are comparable and permit regional and global aggregation.

Only about one third of all countries/territories has complete, reliable data available, and do not require additional estimations. For another third, country-reported estimates of maternal mortality are adjusted for the purposes of comparability. For the final third— those countries with no appropriate maternal mortality data—a statistical model is employed to predict maternal mortality levels. However, the point estimates calculated with this methodology might not represent true levels of maternal mortality. It is advised to consider the estimates together with the reported uncertainty margins within which the true levels are thought to lie.

The ability to generate country, regional, and global estimates with higher precision and accuracy would be greatly facilitated if country civil registration systems were further improved. This improvement would reduce the need to conduct special maternal mortality studies (which are time-consuming, expensive, and of limited use in monitoring trends).

Regional and sub-regional estimates are weighted averages of the country data, using the total number of live births in each country as the weight. Regional aggregates are presented only if available data cover at least 50 per cent of total births in the regional grouping.

SUPPLEMENTARY INFORMATION



EXAMPLES



REFERENCES

Hill, K., K. Thomas, C. Abouzahr, N. Walker, L. Say, M. Inoue and E. Suzuki, on behalf of the Maternal Mortality Working Group (2007). Estimates of maternal mortality worldwide between 1990 and 2005: an assessment of available data. Lancet, vol. 370, Issue 9595, pp. 1311–1319.

Say L. and R.C. Pattinson (2008). Maternal Mortality and Morbidity. In International Encyclopedia of Public Health, eds. Kris Heggenhougen and Stella R. Quah, pp. 222–236. Oxford: Academic Press.

United Nations Population Fund (annual). State of World Population. New York. Available from http://www.unfpa.org/swp/swpmain.htm.

United Nations Population Fund (1998). Issues in measuring and monitoring maternal mortality: implications for programmes. Technical and Policy Paper No.1. New York.

World Health Organization (2009). International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10). Geneva. Available from http://www.who.int/classifications/icd.

World Health Organization and United Nations Children’s Fund (1997). The Sisterhood Method for Estimating Maternal Mortality: Guidance Notes for Potential Users. Geneva. Available from http://www.who.int/reproductivehealth/publications/monitoring/RHT_97_28/en/index.html.

World Health Organization, United Nations Children’s Fund, United Nations Population Fund and World Bank (2010). Trends in Maternal Mortality: 1990 to 2008. Geneva. Available from http://www.who.int/reproductivehealth/publications/monitoring/9789241500265/en/index.html.

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