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Regression Models

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Regression Models: BACKGROUND

In the last decade or so, model-based analyses have become important sources of global information on the prevalence of maternal mortality, largely because of the absence of reliable national level empirical data on maternal mortality throughout the world, particularly in developing countries.

United Nations (WHO/UNICEF/UNFPA) models use statistical regression to predict the proportion of maternal deaths among deaths of women of reproductive age. The regression coefficients are based on models built using countries with good data from both developed and developing countries. The independent (predictor) variables chosen need to be almost universally available and have an intuitive link to maternal mortality. The resulting models explain a high proportion of variance.

Predictors used vary but as shown below include general fertility rate (GFR), skilled attendants at delivery, gross national product (GNP), completeness of vital registration and regional dummy variables among others.

Initial attempts to model the maternal mortality ratio were abandoned in favour of modelling the proportion of maternal deaths of women of reproductive age (PMDF). This made better use of good registration data and used the more reliable characteristics of sisterhood data (the proportion of deaths that were pregnancy-related versus level of mortality). Four models have been developed so far: 1990, 1995, 2000, and 2005. There have also been other models built or proposed.

Advantages:

Limitations:

1990 WHO/UNICEF Model*:

*NB 1990 Model not published

1995 WHO/UNICEF/UNFPA Model:


2000 WHO/UNICEF/UNFPA:

2005 WHO/UNICEF/UNFPA:

The UN models predict the proportion of maternal deaths among deaths of females of reproductive age (PMDF). This is then applied to estimates of adult female deaths and births to calculate the maternal mortality ratio (MMR), the maternal mortality rate (MMRate) and lifetime risk (LTR). For example, in 2005, the estimated PMDF was applied to the 2005 WHO figures for non-HIV/AIDS reproductive-aged female deaths, to obtain the estimated total number of maternal deaths. The number of maternal deaths divided by the 2005 UNDP estimates of the number of live births gave the point estimate for MMR in 2005. The uncertainty limits were derived from model estimates of the standard error of the forecast.

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1990 Model:

World Health Organisation World Health Organization and United Nations Children's Fund. Revised 1990 estimates of maternal mortality: a new approach by WHO and UNICEF. Geneva: WHO; April 1996. (Document WHO/ FRH/MSM/96.11; UNICEF/PLN/96.1)

Documentation on the development of the 1990 models:

World Health Organisation WHO/UNICEF/UNFPA Americas region consultation on maternal mortality estimates. Washington D.C. - April 1998
UNICEF
UNFPA

World Health Organisation WHO/UNICEF/UNFPA Asia Region consultation on maternal mortality estimates. Bangkok, Thailand - June 1998.
UNICEF
UNFPA

1995 Model:

World Health Organisation WHO, UNICEF and UNFPA, Maternal Mortality in 1995, Estimates developed by WHO, UNICEF and UNFPA (WHO/RHR/01.9, Geneva, 2001).
UNICEF
UNFPA

Bulletin of the World Health Organisation

2000 Model:

World Health Organisation WHO, UNICEF and UNFPA. Maternal Mortality in 2000 Estimates developed by WHO, UNICEF and UNFPA, 2003. WHO Department of Reproductive Health and Research. Geneva, 2004.
UNICEF
UNFPA

2005 Model:

World Health Organisation WHO, UNICEF and UNFPA. Maternal Mortality in 2005 Estimates developed by WHO, UNICEF, UNFPA and The World Bank, 2007.
UNICEF
UNFPA

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