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) 

ICD-10 (US Death Certificate) Definitions

‘‘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.
MatMort_DefinitionsTable

(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 or among different countries to ensure that the definitions used are similar or corrections have been made.