Maternal Mortality


Maternal Mortality

Maternal death is defined as one that occurs during pregnancy or within 42 days of the end of a pregnancy, irrespective of the duration and site of the pregnancy, from any cause related to or aggravated by a woman's pregnancy, but not from accidental or incidental cause. Maternal mortality rates are calculated as the number of maternal deaths in a calendar year divided by the number of live births for the same period, multiplied by 100,000. The number of live births used in the denominator is an approximation of the population of pregnant women who are at risk of a maternal death. The numerator is calculated using data from the Final Mortality File from NCHS, included in these deaths assigned an underlying cause of death ICD-10 code of A34, O00-O95, or O98-O99. The denominator is calculated using data from the Natality File from NCHS.

An update to the maternal mortality calculation method in 2018 introduces two new practices. The first change attempts to reduce reporting errors that lead to over-representation of maternal deaths among older women and the second update makes changes to the coding practices for maternal deaths.

From 2003-2017 a checkbox was added to the death certificate to indicate whether the decedent was pregnant at the time of death or up to a year before the death occurred. This was previously used for deaths of a person aged 10-54 years of age. The checkbox still remains, however, the 2018 change reflects a practice to reduce the use of the checkbox to only those aged 10-44.

The second change states that if the checkbox is the only indication of a pregnancy for decedents aged 10-44, a maternal code will be assigned as the underlying cause, except in cases where the underlying cause is an externa or incidental cause. This change allows more information from the death certificate to be retained in the underlying cause of death reporting.

These changes will be reflected in all maternal mortality data starting with the 2018 reporting year and will be incorporated going forward. (2)


1. Hoyert DL, Heron MP, Murphy SL, Kung H. Deaths: Final Data for 2003. National vital statistics reports; vol 54 no 13. Hyattsville, MD: National Center for Health Statistics. 2006.

2. Hoyert DL, Minino AM. Maternal Mortality in the United States: Changes in Coding, Publication, and Data Release, 2018. National Vital Statistic Reports; vol 69 no 2. Hyattsville, MD: National Center for Health Statistics. 2020.

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