Identifying Pregnancy Deaths in the United States, 1999-2005 Vital Statistics and Surveillance...

Identifying Pregnancy Deaths in the United States, 1999-2005

Vital Statistics and Surveillance Systems

Andrea MackayAndrea Mackay

National Center for Health Statistics

ESA/STAT/AC.219/30

Deaths from pregnancy complicationsImportant 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

Background

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

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

Maternal mortality ratio (MMR) and Pregnancy-related mortality ratio (PMR): United States, 1979-2006

Dea

ths

per 1

00,0

00 li

ve b

irths

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

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.

Results

Mortality ratios* increased significantly over time

1999-2002 2003-2005Maternal 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

Pregnancy mortality ratios for states categorized by their death certificate’s pregnancy checkbox status in 2005: United States, 2002 and 2005

Ratio Year

Standard checkbox

Non-standard checkbox/question

No pregnancy checkbox

Maternal mortality* 2002 12.6 12.3 12.2

2005 19.6 14.0 13.8

Absolute change (increase) 7.0 1.7 1.6

Percent change (increase) 55.6% 13.8% 13.1%

Pregnancy-related mortality*2002 15.3 14.0 14.2

2005 22.3 16.7 15.9




ConclusionsNo 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 1999-200212.9% increase in the MMR16.6% increase in the PMR

Ratios increased even more with use of the pregnancy checkbox in 2003

Between 1999-2002 and 2003-200516.7% in the MMR23.1% in the PMR

Conclusions Estimated mortality ratios are higher than:

WHO et al reported U.S. MMR of 11.0 for 2005Hogan 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

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

1999-2002 2003-2005

Total

Maternaldeath

(O00-95,O98-99)

Latematernal

Death (O96)

Pregnancy-related, but

coded outsidechapter O

Total

Maternaldeath

(O00-95,O98-99)

Latematernal

death (O96)



NVSS only (not reported in PMSS)

90 89 1 n/a

283 206 77n/a

Both PMSS and NVSS 1432 1404 28 1377 1244 133

PMSS only(not coded maternal or late maternal in NVSS)

838 n/a 838 571 n/a 571

Total 2360 1493 29 838 2231 1450 210 571

Identifying Pregnancy Deaths in the United States, 1999-2005

Vital Statistics and Surveillance Systems

Andrea MackayAndrea Mackay

National Center for Health Statistics

Deaths from pregnancy complicationsImportant 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

Background

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

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

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

Maternal mortality ratio (MMR) and Pregnancy-related mortality ratio (PMR): United States, 1979-2006

Dea

ths

per 1

00,0

00 li

ve b

irths

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

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

EXAMPLE

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.

Matched Live Birth Certificate from PMSS

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.

Results

Mortality ratios* increased significantly over time

1999-2002 2003-2005Maternal 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


Pregnancy mortality ratios for states categorized by their death certificate’s pregnancy checkbox status in 2005: United States, 2002 and 2005

Ratio Year

Standard checkbox

Non-standard checkbox/question

No pregnancy checkbox

Maternal mortality* 2002 12.6 12.3 12.2

2005 19.6 14.0 13.8



Pregnancy-related mortality*2002 15.3 14.0 14.2

2005 22.3 16.7 15.9




ConclusionsNo 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 1999-200212.9% increase in the MMR16.6% increase in the PMR

Ratios increased even more with use of the pregnancy checkbox in 2003

Between 1999-2002 and 2003-200516.7% in the MMR23.1% in the PMR

Conclusions Estimated mortality ratios are higher than:

WHO et al reported U.S. MMR of 11.0 for 2005Hogan 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

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

1999-2002 2003-2005

Total

Maternaldeath

(O00-95,O98-99)

Latematernal

Death (O96)



Total

Maternaldeath

(O00-95,O98-99)

Latematernal

death (O96)



NVSS only (not reported in PMSS)

90 89 1 n/a

283 206 77n/a

Both PMSS and NVSS 1432 1404 28 1377 1244 133

PMSS only(not coded maternal or late maternal in NVSS)

838 n/a 838 571 n/a 571

Total 2360 1493 29 838 2231 1450 210 571

Identifying Pregnancy Deaths in the United States, 1999-2005 Vital Statistics and Surveillance...

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