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Andrea Mackay National Center for Health Statistics ESA/STAT/AC.219/30

Identifying Pregnancy Deaths in the United States, 1999-2005 Vital Statistics and Surveillance Systems. Andrea Mackay National Center for Health Statistics ESA/STAT/AC.219/30. Background. Deaths from pregnancy complications Important measure of maternal health

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Andrea Mackay National Center for Health Statistics ESA/STAT/AC.219/30

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  1. Identifying Pregnancy Deaths in the United States, 1999-2005 Vital Statistics and Surveillance Systems Andrea Mackay National Center for Health Statistics ESA/STAT/AC.219/30

  2. Background • Deaths from pregnancy complications • Important measure of maternal health • Sentinel public health indicator • A woman’s risk of dying from pregnancy complications has • decreased dramatically over the past century in the U.S. • 1999-2005: reported increases in the number and rates of U.S. maternal deaths, coinciding with: • Implementation of the Tenth Revision of the International • Classification of Diseases (ICD-10), used to classify the • underlying causes of death • The 2003 revision of the U.S. Standard Certificate of Death • with a pregnancy status checkbox

  3. The U.S. Standard Certificate of Death (2003 revision) includes a pregnancy status checkbox If FEMALE: • Not pregnant within past year • Pregnant at time of death • Not pregnant, but pregnant within 42 days of death • Not pregnant, but pregnant 43 days to 1 year before death • Unknown if pregnant within the past year Not all states have implemented the 2003 revision In 2005, 18 states had adopted the 2003 revision Other states used a non-standard checkbox or no checkbox Non-standard checkbox: no option for deaths within 42 days

  4. Two national sources of data on pregnancy deaths • National Vital Statistics System (NVSS) • Reports on maternal and late maternal deaths • WHO 42-day post-pregnancy interval for maternal deaths • Deaths coded using ICD-10 and WHO coding guidelines • Uses only information in Part I and Part II of the death certificate • Cause of death: ICD-10 codes O00-95, O98-99, and O96 • Pregnancy Mortality Surveillance System (PMSS) • Reports on pregnancy-related deaths • 1 year post-pregnancy interval • Uses all available information on the death certificate and matched birth certificates and other sources when available • Cause of death: classified into groups, i.e. infection, embolism, hemorrhage

  5. Maternal mortality ratio (MMR) and Pregnancy-related mortality ratio (PMR): United States, 1979-2006 Deaths per 100,000 live births

  6. Effects of a pregnancy status check box on the death certificate • Improves the identification of maternal deaths using death certificates • Makes the death certificate a more valuable source for the surveillance system • Reduces the differential between the numbers of pregnancy deaths identified in CDC’s two data systems • Can lead to misclassification of some deaths as maternal or late maternal when the cause of death is not pregnancy-related

  7. Analysis of U.S. Pregnancy mortality 1999-2005 Combined all pregnancy deaths from NVSS and PMSS to obtain a combined, unduplicated count: Maternal deaths (during or within 42 days of pregnancy) Pregnancy-related deaths (during or within 1 year of pregnancy) Evaluated separately the effects of ICD-10 and the pregnancy status checkbox: Data were stratified into 2 time periods: 1999-2002 and 2003-2005 Some maternal and late maternal deaths in NVSS that matched to deaths in PMSS were determined to be: Not causally related to pregnancy and excluded from the analysis Not temporally related to pregnancy and excluded from the analysis Misclassified (maternal as late maternal, and vice versa) by additional temporal information available in PMSS, and were reclassified appropriately.

  8. Results Mortality ratios* increased significantly over time 1999-2002 2003-2005 Maternal mortality (MMR) 13.1 15.3 Pregnancy-related mortality (PMR) 14.7 18.1 And were higher than those reported separately by either system NVSS reported MMR ~9.6 ~13.4 PMSS reported PMR ~14.1 ~15.8 * Deaths per 100,000 live births

  9. Pregnancy mortality ratios for states categorized by their death certificate’s pregnancy checkbox status in 2005: United States, 2002 and 2005 * Deaths per 100,000 live births

  10. Conclusions No single system identifies all deaths due to pregnancy. Combining data from two systems provides a more precise measurement of maternal mortality. Mortality ratios increased after the implementation of ICD-10 in 1999: Between 1995-1997 and 1999-2002 12.9% increase in the MMR 16.6% increase in the PMR Ratios increased even more with use of the pregnancy checkbox in 2003 Between 1999-2002 and 2003-2005 16.7% in the MMR 23.1% in the PMR

  11. Conclusions Estimated mortality ratios are higher than: WHO et al reported U.S. MMR of 11.0 for 2005 Hogan et al (Lancet) estimated U.S. PMR of 17.0 for 2008 Use of a standard format checkbox increases ascertainment of pregnancy deaths. Mortality ratios increased significantly between 2002 and 2005 in states using a standard format checkbox in 2005 No significant increase in states without a checkbox in 2005 As more states adopt the 2003 revision of the U.S. Standard Certificate of Death, with the checkbox, mortality ratios in the U.S. may continue to increase Significant changes in the leading causes of death • More maternal deaths from indirect causes of death identified with checkbox • Cardiovascular complications and non-cardio medical conditions became the leading causes of pregnancy death

  12. Final analytic data set: deaths due to pregnancy,1999-2002 and 2003-2005

  13. Identifying Pregnancy Deaths in the United States, 1999-2005 Vital Statistics and Surveillance Systems Andrea Mackay National Center for Health Statistics

  14. Background • Deaths from pregnancy complications • Important measure of maternal health • Sentinel public health indicator • A woman’s risk of dying from pregnancy complications has • decreased dramatically over the past century in the U.S. • 1999-2005: reported increases in the number and rates of U.S. maternal deaths, coinciding with: • Implementation of the Tenth Revision of the International • Classification of Diseases (ICD-10), used to classify the • underlying causes of death • The 2003 revision of the U.S. Standard Certificate of Death • with a pregnancy status checkbox

  15. Changes in Coding Under ICD-10 ICD-10 includes a new classification (O96) for late maternal deaths (those occurring 43-365 days after termination of pregnancy) ICD-10 coding guidelines allow deaths from indirect causes to be classified as maternal if the pregnancy is reported in Part I or Part II of the death certificate ICD-10 recommends the inclusion of a pregnancy status checkbox on the death certificate • Provides a temporal relationship between pregnancy and death • Can be used in determining a maternal/late maternal death

  16. The U.S. Standard Certificate of Death (2003 revision) includes a pregnancy status checkbox If FEMALE: • Not pregnant within past year • Pregnant at time of death • Not pregnant, but pregnant within 42 days of death • Not pregnant, but pregnant 43 days to 1 year before death • Unknown if pregnant within the past year Not all states have implemented the 2003 revision In 2005, 18 states had adopted the 2003 revision Other states used a non-standard checkbox or no checkbox Non-standard checkbox: no option for deaths within 42 days

  17. Two national sources of data on pregnancy deaths • National Vital Statistics System (NVSS) • Reports on maternal and late maternal deaths • WHO 42-day post-pregnancy interval for maternal deaths • Deaths coded using ICD-10 and WHO coding guidelines • Uses only information in Part I and Part II of the death certificate • Cause of death: ICD-10 codes O00-95, O98-99, and O96 • Pregnancy Mortality Surveillance System (PMSS) • Reports on pregnancy-related deaths • 1 year post-pregnancy interval • Uses all available information on the death certificate and matched birth certificates and other sources when available • Cause of death: classified into groups, i.e. infection, embolism, hemorrhage

  18. Maternal mortality ratio (MMR) and Pregnancy-related mortality ratio (PMR): United States, 1979-2006 Deaths per 100,000 live births

  19. Effects of a pregnancy status check box on the death certificate • Improves the identification of maternal deaths using death certificates • Makes the death certificate a more valuable source for the surveillance system • Reduces the differential between the numbers of pregnancy deaths identified in CDC’s two data systems • Can lead to misclassification of some deaths as maternal or late maternal when the cause of death is not pregnancy-related

  20. EXAMPLE Information about the temporal relationship to pregnancy is sometimes missing, with no other indication of a death related to pregnancy.

  21. Matched Live Birth Certificate from PMSS For this example, information about the temporal relationship to pregnancy was available from a matched live birth certificate, which indicated that the woman delivered, by Cesarean section, 26 days prior to her death. A marked pregnancy status checkbox, indicating that death occurred within 42 days of pregnancy, would have provided a temporal relationship.

  22. Analysis of U.S. Pregnancy mortality 1999-2005 Combined all pregnancy deaths from NVSS and PMSS to obtain a combined, unduplicated count: Maternal deaths (during or within 42 days of pregnancy) Pregnancy-related deaths (during or within 1 year of pregnancy) Evaluated separately the effects of ICD-10 and the pregnancy status checkbox: Data were stratified into 2 time periods: 1999-2002 and 2003-2005 Some maternal and late maternal deaths in NVSS that matched to deaths in PMSS were determined to be: Not causally related to pregnancy and excluded from the analysis Not temporally related to pregnancy and excluded from the analysis Misclassified (maternal as late maternal, and vice versa) by additional temporal information available in PMSS, and were reclassified appropriately.

  23. Results Mortality ratios* increased significantly over time 1999-2002 2003-2005 Maternal mortality (MMR) 13.1 15.3 Pregnancy-related mortality (PMR) 14.7 18.1 And were higher than those reported separately by either system NVSS reported MMR ~9.6 ~13.4 PMSS reported PMR ~14.1 ~15.8 * Deaths per 100,000 live births

  24. Pregnancy mortality ratios for states categorized by their death certificate’s pregnancy checkbox status in 2005: United States, 2002 and 2005 * Deaths per 100,000 live births

  25. Conclusions No single system identifies all deaths due to pregnancy. Combining data from two systems provides a more precise measurement of maternal mortality. Mortality ratios increased after the implementation of ICD-10 in 1999: Between 1995-1997 and 1999-2002 12.9% increase in the MMR 16.6% increase in the PMR Ratios increased even more with use of the pregnancy checkbox in 2003 Between 1999-2002 and 2003-2005 16.7% in the MMR 23.1% in the PMR

  26. Conclusions Estimated mortality ratios are higher than: WHO et al reported U.S. MMR of 11.0 for 2005 Hogan et al (Lancet) estimated U.S. PMR of 17.0 for 2008 Use of a standard format checkbox increases ascertainment of pregnancy deaths. Mortality ratios increased significantly between 2002 and 2005 in states using a standard format checkbox in 2005 No significant increase in states without a checkbox in 2005 As more states adopt the 2003 revision of the U.S. Standard Certificate of Death, with the checkbox, mortality ratios in the U.S. may continue to increase Significant changes in the leading causes of death • More maternal deaths from indirect causes of death identified with checkbox • Cardiovascular complications and non-cardio medical conditions became the leading causes of pregnancy death

  27. Final analytic data set: deaths due to pregnancy,1999-2002 and 2003-2005

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