Definitions
Maternal Mortality Rate vs Ratio
Maternal mortality is calculated by counting deaths associated with any pregnancy outcome (livebirth, stillbirth, ectopic, termination or miscarriage) in the numerator and using all livebirths as the denominator. Thus, there are multiple cases in the numerator that are not present in the denominator indicating that the proper term would be "Maternal Mortality Ratio." However, the use of "Maternal Mortality Rate" is so ingrained in the literature that ACOG, CDC and most current authors continue to use "Maternal Mortality Rate." Therefore, in this website, we use "Maternal Mortality Rate."
CDC/ACOG Definitons
Pregnancy-associated death: The death of a woman while pregnant or within 1 year of termination of pregnancy, irrespective of cause.
Pregnancy-related death: The death of a woman while pregnant or within 1 year of termination of pregnancy, irrespective of the duration and site of the pregnancy, from any cause related to or aggravated by her pregnancy or its management, but not from accidental or incidental causes.
(From: Berg C, Danel I, Atrash H, Zane S, Bartlett L (Editors). Strategies to reduce pregnancy-related deaths: from identification and review to action. Atlanta: Centers for Disease Control and Prevention; 2001. NOTE: 2.9MB)
WHO/NCHS (US Death Certificate) Definitions
Uses ICD-10 codes from the Death Certificate to identify cause of death, restricted to ICD-10 codes A34, O00-O95, O98-O99. See link for definitions of the ICD-10 pregnancy codes
‘‘Maternal deaths’’ are defined by the World Health Organization as ‘‘the death of a woman while pregnant or within 42 days of termination of pregnancy, irrespective of the duration and the site of the pregnancy, from any cause related to or aggravated by the pregnancy or its management, but not from accidental or incidental causes.’’
‘‘Late maternal deaths’’ are defined as ‘‘the deaths of a woman from direct or indirect obstetric causes more than 42 days but less than one year after termination of pregnancy.’’
‘‘Pregnancy-related deaths’’ are defined as ‘‘the death of a woman while pregnant or within 42 days of termination of pregnancy, irrespective of the cause of death.’’
‘‘Direct obstetric deaths: those resulting from obstetric complications of the pregnant state (pregnancy, labour and puerperium), from interventions, omissions, incorrect treatment, or from a chain of events resulting from any of the above.’’
‘‘Indirect obstetric deaths: those resulting from previous existing disease or disease that developed during pregnancy and which was not due to direct obstetric causes, but which was aggravated by physiologic effects of pregnancy.’’
(From: Hoyert DL. Maternal mortality and related concepts. National Center for Health Statistics. Vital Health Stat 3(33). 2007. This article is an excellent discussion of the impact of changing definitions on the Maternal Mortality rate.)
Two Sets of Terms
Having two sets of definitions and terms can be confusing. However, each set has a different purpose.
ICD10 Terms
- Used by many nations, so they require coding conventions to be applied in a comparable fashion.
- Used to monitor trends and make comparisons.
- Only cause-of-death data from death certificates can be used to identify deaths that meet ICD definitions.
ACOG/CDC Terms
- Used by individual states or cities.
- Used to identify deaths for review and action.
- A variety of data sources, including vital records and hospital data, can be used to identify deaths that meet ACOG/CDC definitions.
(From: Berg C, et.al. see above)
The upshot of these competing definitions is that one has to be extraordinarily careful when comparing Maternal Mortality rates among different time periods, among different countries or between different papers to ensure that the definitions used are similar or corrections have been made.
Technical Definitions used by CA Department of Public Health
MATERNAL MORTALITY RATE:
Death from obstetric causes <42 days postpartum, per 100,000 live births
Numerator: Underlying cause of death on the death certificate:
ICD-10 codes A34, O00-O95, O98-O99 for 1999-present
ICD-9 codes 630-638, 640-648, 650-676 for 1979-1998
Denominator: Live Births in California per year
Thi is the same method as national rates calculated by National Center for Health Statistics.
Benchmark for Healthy People 2010 objective of 4.3 maternal deaths per 100,000 live births.
Used for reporting vital statistics and comparison of indicators and objectives.
PREGNANCY-RELATED MORTALITY RATE:
Death from obstetric causes within one year postpartum, per 100,000 live births
Numerator: Underlying cause of death on the death certificate:
ICD-10 codes A34, O00-O96, O98-O99 for 1999-present
Note that code O96 is sepcifiaclly for deaths from any obstetric cause occuring between 42 and 365 days after delivery.
Code O97 is used to classify deaths from any direct obstetric cause which occur one year or more after termination of the pregnancy, and
is excluded from both rates.
Denominator: Live Births in California per year
