Definition
The maternal mortality ratio is the number of women who die 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. The 10th revision of the International Classification of Diseases makes provision for including late maternal deaths occurring between six weeks and one year after childbirth.
Goal/target addressed
Goal 5. Improve maternal health.
Target 6. Reduce by three quarters, between 1990 and 2015, the maternal mortality ratio.
Rationale
The indicator, which is directly related to the target, monitors deaths related to pregnancy. Such deaths are affected by various factors, including general health status, education and services during pregnancy and childbirth. It is important to monitor changes in health conditions related to sex and reproduction.
Method of computation
The maternal mortality ratio can be 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 indicator can be calculated directly from data collected through vital statistics registrations, household surveys or hospital studies. However, these all have data quality problems (see “Data collection and sources”). Alternative methods include a review of all deaths of women of reproductive age (so-called Reproductive Age Mortality Surveys, or RAMOS), longitudinal studies of pregnant women and repeated household studies. All these methods, however, still rely on accurate reporting of deaths of pregnant women and of the cause of death, something that is difficult to obtain in reality.
Another problem is the need for large sample sizes, which raises costs. This can be overcome by using sisterhood methods. The indirect sisterhood method asks respondents four simple questions about how many of their sisters reached adulthood, how many have died and whether those who died were pregnant around the time of death. However, the reference period of the estimate is at least 10–12 years before the survey. The direct sisterhood method used in Demographic and Health Surveys also asks respondents to provide the date of death, which permits the calculation of more recent estimates, but even then the reference period tends to center on 0–6 years before the survey.
Maternal deaths should be divided into two groups. Direct obstetric deaths result from obstetric complications of the pregnant state (pregnancy, labour and puerperium); from interventions, omissions or incorrect treatment; or from a chain of events resulting from any of these. Indirect obstetric deaths result from previously existing disease or disease that developed during pregnancy and that was not directly due to obstetric causes but was aggravated by the physiologic effects of pregnancy. Published maternal mortality ratios should always specify whether the numerator (number of recorded maternal deaths) is the number of recorded direct obstetric deaths or the number of recorded obstetric deaths (direct plus indirect). Maternal deaths from HIV/AIDS and obstetrical tetanus are included in the maternal mortality ratio.
Data collection and source
Good vital statistics registration systems are rare in developing countries. Official data are usually obtained from health service records, but few women in rural areas have access to health services. So in developing countries, it is more usual to use survey data. The most common sources of data are the Demographic and Health Surveys and similar household surveys. Available data on levels of maternal mortality are generally significantly underestimated because of problems of misclassification and under-reporting of maternal deaths. The World Health Organization, the United Nation’s Children’s Fund and the United Nations Population Fund have adjusted to existing data to account for these problems and have developed model-based estimates for countries with no reliable national data on maternal mortality. It is these estimates that are usually published in international tables.
References
Maternal Mortality in 1995, 2001, World Health Organization, United Nations Children’s Fund and United Nations Population Fund.
The Sisterhood Method for Estimating Maternal Mortality: Guidance Notes for Potential Users, 1997, World Health Organization and United Nation’s Children’s Fund.
Maternal Mortality: A Global Factbook, 1991, World Health Organization.
“Issues in Measuring and Monitoring Maternal Mortality: Implications for Programmes”, Technical and Policy Paper 1, 1998, United Nation’s Population Fund.
The State of the World’s Children, annual, United Nations Children’s Fund (www.unicef.org/publications).
World Development Indicators, annual, World Bank (www.worldbank.org/data).
Human Development Report, annual, United Nations Development Programme (www.undp.org).
Reduction of Maternal Mortality: A Joint WHO/UNFPA/UNICEF/World Bank Statement, 1999, World Health Organization (www.who.int/reproductive-health).
Periodicity of measurement
Every 7–10 years.
Gender 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 and good nutrition as well as to the economic resources needed to pay for health care or family planning services.
International data comparisons
The World Health Organization, the United Nation’s Children’s Fund and the United Nations Population Fund have adjusted to existing data to account for these problems and have developed model-based estimates for countries with no reliable national data on maternal mortality. It is these estimates that are usually published in international tables.
The State of the World’s Children, annual, United Nations Children’s Fund (www.unicef.org/publications).
World Development Indicators, annual, World Bank (www.worldbank.org/data).
Human Development Report, annual, United Nations Development Programme (www.undp.org).
Comments and limitations
This indicator is generally of unknown reliability, as are many other cause-specific mortality indicators, because of the difficulty in distinguishing deaths that are genuinely related to pregnancy from deaths that are not. Even in industrialized countries with comprehensive vital statistics registration systems, misclassification and under-reporting of maternal deaths can lead to serious underestimation. Because it is a relatively rare event, huge sample sizes are needed if household surveys are used. Household surveys such as the Demographic and Health Survey attempt to measure maternal mortality by asking respondents about survivorship of sisters. While the sisterhood method reduces sample size requirements, it produces estimates for covering some 6–12 years before the survey, which renders the data problematic for monitoring progress or observing the impact of interventions. In addition, due to the very large confidence limits around the estimates, they are not suitable for assessing trends over time or for making comparisons between countries. As a result, it is recommended that process indicators, such as attendance by skilled health personnel at delivery and use of emergency obstetric care facilities be used to assess progress towards the reduction in maternal mortality.
The maternal mortality ratio should not be confused with the maternal mortality rate (whose denominator is the number of women of reproductive age), which measures the likelihood of both becoming pregnant and dying during pregnancy or the puerperium (six weeks after delivery). The maternal mortality ratio (whose denominator is the number of live birth), takes fertility levels (likelihood of becoming pregnant) into consideration.
Agencies
Ministries of health.
United Nations Children’s Fund.
World Health Organization.
United Nations Population Fund.