Data sources for measuring maternal mortality

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Data sources for measuring maternal mortality

• November 1, 2010
• Rafael Lozano
• Professor of Global Health

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Outline

• Input data and correction process by source
• PMDF to maternal deaths to rates
• Modeling approaches I linear models
• Outlier detection
• Modeling approaches II space-time regression
• Predictive validity
• Uncertainty

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Processing input data
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Four major categories of data

• Vital registration
• Deaths in the household data from censuses and
  surveys
• Sibling histories from surveys
• National and subnational peer reviewed studies of
  maternal mortality (i.e. verbal autopsy studies,
  etc)

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Four major categories of data

• Vital registration
• Deaths in the household data from censuses and
  surveys
• Sibling histories from surveys
• National and subnational peer reviewed studies of
  maternal mortality (i.e. verbal autopsy studies,
  etc)

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Sources for vital registration data

• WHO Mortality Database
• Reported civil registration data from countries
• Periodically updated and released by WHO
• Country websites and official publications
• Sample registration systems, such as in India or
  China

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Issues with vital registration

• Changes in the International Classification of
  Diseases (ICD) results in changes in coding
  assignments to underlying causes of death
• The use of tabulation lists in the ICD results in
  the loss of substantial detail of cause of death
• Deaths can be (and often are) assigned to causes
  that should not be considered underlying causes
  of death (garbage codes)
• Together, this means that what counts as a
  maternal death in one country in one year, may
  not count as a maternal death in another
  country or another year.

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Correcting vital registration

• Shortened cause of death list 56 causes of
  interest to public health practitioners
• Causes mapped across ICD revisions to these 56
  causes
• Maternal conditions encompass all O codes (O00
  O99)

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Garbage codes

• Garbage coding is the biggest challenge to
  comparability across countries and over time in
  vital registration data
• Garbage codes assigned causes of death which are
  not useful for public health analysis of
  cause-of-death data
• General approach to address problem
• Identify garbage codes
• Identify target codes to which garbage codes
  should be reassigned
• Choose the fraction of deaths assigned to a
  garbage code that should be reassigned to each
  target code

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Fraction of deaths assigned to GCs in the latest
ICD-10 year since 2000
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Garbage codes

• General approach to address problem
• Identify garbage codes
• Identify target codes to which garbage codes
  should be reassigned
• Choose the fraction of deaths assigned to a
  garbage code that should be reassigned to each
  target code

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Redistribution of garbage codes

• Identify garbage codes
• 4 classifications of garbage codes
• Type 1 Causes that should not be considered
  underlying causes of death
• i.e. R95-R99 Ill-defined and unknown causes of
  mortality
• Type 2 Intermediate causes of death
• i.e. I51 Heart failure
• Type 3 Immediate causes of death
• i.e. E87 Other disorders of fluid, electrolyte
  and acid-base balance
• Type 4 Unspecified causes within a larger
  grouping
• i.e. Malignant neoplasm without specification of
  site

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Percentage of Type of Garbage Codes
All country years by ICD
All country years by age, only ICD 10
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Redistribution of garbage codes

• Identify target codes to which garbage codes
  should be reassigned
• Based on pathophysiology, i.e.

Garbage code
Target causes
Digestive diseases
Genitourinary diseases
Peritonitis
Maternal conditions
Injuries
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Redistribution of garbage codes

• Choose the fraction of deaths assigned to a
  garbage code that should be reassigned to each
  target code
• 3 approaches
• Proportionate redistribution
• For causes with little information content
• Statistical models
• For heart failure
• Expert judgment
• Via review of published literature and
  consultation with experts, taking into account
  time trends in causes of death

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Garbage codes redistributed to maternal causes,
based on expert judgment (ICD-10)
ICD-10 code Condition Fraction to maternal
D65 Disseminated intravascular coagulation defibrination syndrome  30
K65 Peritonitis  20
A40 Streptococcal septicaemia  14
A41 Other septicaemia  14
I26 Pulmonary embolism  10
K66.0 Peritoneal adhesions  50
N17 Acute renal failure 0.4
N18 Chronic renal failure 0.4
N19 Unspecified renal failure 0.4
R57.9 Shock, unspecified 25
R57.1 Hypovolaemic shock 35
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Garbage codes redistributed to maternal causes,
based on proportions (ICD-10)
ICD-10 code Condition
R99 Other ill-defined and unspecified causes of mortality
R98 Unattended death
R09.2 Respiratory arrest
R96.0 Instantaneous death
R68.8 Other specified general symptoms and signs
R55 Syncope and collapse
R50.9 Fever, unspecified
R96.1 Death occurring less than 24 hours from onset of symptoms, not otherwise explained
R57.0 Cardiogenic shock
R56.8 Other and unspecified convulsions
R62.8 Other lack of expected normal physiological development
R10.4 Other and unspecified abdominal pain
R58 Haemorrhage, not elsewhere classified
R57.1 Hypovolaemic shock
R09.0 Other symptoms and signs involving the circulatory and respiratory systems
R02 Gangrene, not elsewhere classified
R40.2 Coma, unspecified
R04.8 Haemorrhage from other sites in respiratory passages
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Maternal Mortality Audit Studies

• 32 studies have been published that use detailed
  audits of reproductive-aged deaths to ascertain
  the true number of maternal deaths compared to
  those registered.
• Assessment of these studies should exclude late
  maternal deaths and incidental causes to make
  them comparable to the GC algorithms for maternal
  mortality estimation.
• 30 studies identify either late maternal and
  incidental deaths, but only 5 studies identify
  both
• These studies provide an opportunity to validate
  the GC approach to maternal death correction.

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Published Studies on Maternal Death
Misclassification
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Four major categories of data

• Vital registration
• Deaths in the household data from censuses and
  surveys
• Sibling histories from surveys
• National and subnational peer reviewed studies of
  maternal mortality (i.e. verbal autopsy studies,
  etc)

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Deaths in the household

• Some censuses and surveys include a module on
  deaths occurring in the household over a
  specified period of time
• Was the deceased between the ages 15-49 and
  female?
• If yes did she die while pregnant? During child
  birth? In the 6 weeks after giving birth or
  terminating the pregnancy?
• Direct questioning about events in the household
  tends to lead to undercounting of vital events

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Household Deaths are Usually Undercounts
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Four major categories of data

• Vital registration
• Deaths in the household data from censuses and
  surveys
• Sibling histories from surveys
• National and subnational peer reviewed studies of
  maternal mortality (i.e. verbal autopsy studies,
  etc)

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Survey data for maternal mortality

• Difficult to capture in a survey because maternal
  deaths are rare a very large sample size
  required
• Sibling histories yield high return of
  observations per respondent
• Availability of large datasets with information
  on sibling survival from household surveys
• DHS maternal mortality module
• CDC Reproductive Health Surveys
• However, naïve analysis of sibling histories can
  be misleading
• Survivor bias
• Recall bias

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Gakidou-King weights

• An algebraic correction for underrepresentation
  of high mortality families
• Upweight observations from high mortality
  families
• Calculate a family-level weight in the survey
  micro-data
• This weight (Wf Bf /Sf) is the inverse of the
  probability of surviving to the time of the
  survey
• Similar to a population sampling weight the
  inverse of the probability of selection into the
  sample

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Four major categories of data

• Vital registration
• Sibling histories from surveys
• Deaths in the household data from censuses and
  surveys
• National and subnational peer reviewed studies of
  maternal mortality (i.e. verbal autopsy studies,
  etc)

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Literature review to identify studies

• In PubMed, searched for maternal mortality and
  country name
• Included studies had to be peer-reviewed,
  population-based, and provide clear description
  of methods
• 25 additional verbal autopsy studies which
  included maternal in the cause list

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Final Database by Source

Source of Data Site-Years of Observation
Vital registration 2186
Sibling Histories 204
Surveillance Systems 20
Census/Survey Deaths in Household 26
National VA 35
Subnational VA 180
Total 2651

• No data for 21 countries, representing 2.2 of
  births

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Density of site-years of observation, 1980-2008
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Density of site-years of observation, 1980-2008
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Data sources in each country

• National and subnational sources included
• Since the time of publication, new data sources
  have come to light
• Italicized incorporated into model since the
  Lancet 2010 publication
• Italicized and in blue font sources that we are
  aware of but have not yet identified and
  incorporated

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Bangladesh
Nationally representative data sources Nationally representative data sources
Year Source
2000-2001 Bangladesh  Maternal Mortality and Maternal Health Services Survey (BMMS) household deaths module, microdata
2001 Bangladesh  Maternal Mortality and Maternal Health Services Survey (BMMS) sibling history microdata
Sub-nationally representative data sources Sub-nationally representative data sources
Year Source
1980-2006 Matlab Demographic Surveillance Site
1982 Alauddin M. Maternal mortality in rural Bangladesh the Tangail district. Stud.Fam.Plann. 198617(1)13-21.
1983 Khan AR, et al. Maternal mortality in rural Bangladesh the Jamalpur district. Stud.Fam.Plann. 19867-12.
1987 Fauveau V, et al.. Effect on mortality of community-based maternity-care programme in rural Bangladesh. The Lancet 1991338(8776)1183-1186.
2000 INDEPTH
2003 Chowdhury ME, et al. Determinants of reduction in maternal mortality in Matlab, Bangladesh a 30-year cohort study. The Lancet 2007370(9595)1320-1328.
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Bhutan
Nationally representative data sources Nationally representative data sources
Year Source
2005 Tabulated census household deaths data
Sub-nationally representative data sources Sub-nationally representative data sources
Year Source
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Cambodia
Nationally representative data sources Nationally representative data sources
Year Source
2000 Demographic and Health Survey (DHS) sibling history microdata
2005 Demographic and Health Survey (DHS) sibling history microdata
2008 Tabulated census household deaths data
Sub-nationally representative data sources Sub-nationally representative data sources
Year Source
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India
Nationally representative data sources Nationally representative data sources
Year Source
1982, 1997, 1999, 2001, 2002, 2004 National Sample Registration Scheme (SRS)
1992 National Family Health Survey I microdata (deaths in the household)
1998 National Family Health Survey II microdata (deaths in the household VA)
1999-2004 District Level Household Survey (DLHS) II microdata (deaths in the HH)
2002 Special Survey Nationwide
2004-2008 District Level Household Survey (DLHS) III microdata (deaths in the HH)
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India, continued
Sub-nationally representative data sources Sub-nationally representative data sources
Year Source
1980-1998 Survey of Causes of death (SCD)
1986 Bhatia JC. Levels and causes of maternal mortality in southern India. Stud.Fam.Plann. 199324(5)310-318.
1989 Gupta N, et al. Maternal mortality in seven districts of Uttar Pradesh - an ICMR Task Force Study. Indian Journal of Public Health 200650(3)173-178.
1990-1998 Medical Certification of Causes of Death (MCCD9)
1992 Kumar R, et al. Maternal mortality inquiry in a rural community of north India. International Journal of Gynecology Obstetrics 198929(4)313-319.
1992 Kakrani V, et al. A study of registration of deaths at primary health centre-with special reference, to. Indian J.Med.Sci. 199650(6)196.
1999-2001 Medical Certification of Causes of Death (MCCD10)
2000 Singh RB, Singh V, Kulshrestha SK, Singh S, Gupta P, Kumar R, et al. Social class and all-cause mortality in an urban population of North India. Acta Cardiol. 2005 Dec60(6)611-617.
2002 Iyengar K, et al. Pregnancy-related deaths in rural Rajasthan, India exploring causes, context, and care-seeking through verbal autopsy. Journal of Health, Population and Nutrition 200927(2)293.
2004 Joshi R, et al. Verbal autopsy coding are multiple coders better than one? Bull.World Health Organ. 20098751-57.
2005 Barnett S, et al. A prospective key informant surveillance system to measure maternal mortality - findings from indigenous populations in Jharkhand and Orissa, India. BMC Pregnancy Childbirth 2008 Feb 2886.
2007 Dongre A, et al. A community based cross sectional study on feasibility of lay interviewers in ascertaining causes of adult deaths by using verbal autopsy in rural Wardha. Online Journal of Health And Allied Sciences 20097(4).
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Indonesia
Nationally representative data sources Nationally representative data sources
Year Source
1994 Demographic and Health Survey (DHS) sibling history microdata
1997 Demographic and Health Survey (DHS) sibling history microdata
2002 Demographic and Health Survey (DHS) sibling history microdata
2007 Demographic and Health Survey (DHS) sibling history microdata
Sub-nationally representative data sources Sub-nationally representative data sources
Year Source
1981 Fortney JA, et al. Reproductive mortality in two developing countries. Am.J.Public Health 1986 Feb76(2)134-138.
2006 Ronsmans C, et al. Professional assistance during birth and maternal mortality in two Indonesian districts. Bull.World Health Organ. 2009 Jun87(6)416-423.
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Lao, Peoples Democratic Republic of
Nationally representative data sources Nationally representative data sources
Year Source
1990 Fauveau VA. The Lao People's Democratic Republic maternal mortality and female mortality determining causes of deaths. World Health Stat.Q. 199548(1)44-46.
Sub-nationally representative data sources Sub-nationally representative data sources
Year Source
Sources that could potentially be incorporated, with access Sources that could potentially be incorporated, with access
1995 Census data
2005 Census data
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Nepal
Nationally representative data sources Nationally representative data sources
Year Source
1996 Demographic and Health Survey (DHS) sibling history microdata
2006 Demographic and Health Survey (DHS) sibling history microdata
Sub-nationally representative data sources Sub-nationally representative data sources
Year Source
Sources that could potentially be incorporated, with access Sources that could potentially be incorporated, with access
2008-2009 National maternal mortality enquiry
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Pakistan
Nationally representative data sources Nationally representative data sources
Year Source
1993-1994 Vital registration
2006 Demographic and Health Survey (DHS) Verbal autopsy microdata
Sub-nationally representative data sources Sub-nationally representative data sources
Year Source
1986, 1990 Fikree FF, et al. Maternal mortality in different Pakistani sites ratios, clinical causes and determinants. Acta Obstet.Gynecol.Scand. 199776(7)637-645.
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The Philippines
Nationally representative data sources Nationally representative data sources
Year Source
1981, 1992-1998, 2001-2005 Vital registration data
1993 Demographic and Health Survey (DHS) sibling history microdata
1998 Demographic and Health Survey (DHS) sibling history microdata
Sub-nationally representative data sources Sub-nationally representative data sources
Year Source
Sources that could potentially be incorporated, with access Sources that could potentially be incorporated, with access
2006 Family Planning Survey
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Sri Lanka
Nationally representative data sources Nationally representative data sources
Year Source
1980-1989, 1991-2006 Vital registration data
Sub-nationally representative data sources Sub-nationally representative data sources
Year Source
Sources that could potentially be incorporated, with access Sources that could potentially be incorporated, with access
ARFH Surveillance data
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Thailand
Nationally representative data sources Nationally representative data sources
Year Source
1980-1987, 1990-2000, 2002-2007 Vital registration data
2004-2006 Chandoevwit W, et al, Using multiple data for calculating the maternal mortality ratio in Thailand, TDRI Quarterly Review. 200722(3)13-19
1995, 1997 BHP studies, via Chandoevwit W, et al, Using multiple data for calculating the maternal mortality ratio in Thailand, TDRI Quarterly Review. 200722(3)13-19
Sub-nationally representative data sources Sub-nationally representative data sources
Year Source
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