An Assessment of Maternal Mortality in the United States, 1995-97

An Assessment of Maternal Mortality in the United States, 1995-97 Andrea MacKay, MSPH Cynthia Berg, MD, MPH Catherine Duran Jeani Chang, MPH Harry Rosenberg, PhD

Source: Achievements in Public Health, 1900-1999: Healthier Mothers and Babies. MMWR. 1999:48(38);849-858

Pregnancy Mortality Background Pregnancy-Related Mortality Surveillance –United States, 1991-1999 MMWR Surveillance Summaries Vol 52 no.SS-2, 2003.

Leading causes of pregnancy-related deathUnited States, 1991-1999 • Embolism (20%) • Hemorrhage (17%) • Hypertensive disorders of pregnancy (16%) • Infection (13%) • Recent increase in deaths from cardiomyopathy (8%) Source: MMWR Surveillance Summaries vol 52 no.ss-2

Distribution of pregnancy-related deaths by outcome of pregnancy, United States 1991-99 Source: MMWR Surveillance Summaries vol 52 no.ss-2

Pregnancy-related deaths by age and race, United States 1991-1999 Source: MMWR Surveillance Summaries vol 52 no.ss-2

An Assessment of Maternal Mortality in the United States, 1995-97

Data sources • National Vital Statistics System (NVSS) National Center for Health Statistics, CDC • Pregnancy-related Mortality Surveillance System (PMSS) Division of Reproductive Health, NCCDPHP, CDC

Maternal Mortality Rate and Pregnancy-related Mortality Ratio, United States, 1979 - 1997

Study Objectives • To compare maternal deaths in NVSS with pregnancy-related deaths in PMSS • To determine the nature and magnitude of reporting differences and to identify possible disparities in reporting by age, race, region, and cause of death • To determine a combined pregnancy mortality ratio based on information from both systems

NVSS National vital registration system Early 1900’s WHO guidelines Coded by MICAR according to algorithm Maternal mortality rates PMSS Voluntary surveillance system Initiated in 1986 CDC/ACOG Reviewed & classified by medical epidemiologists Pregnancy-related mortality ratios NVSS and PMSSWhat are they and how are they different?

NVSS Pregnant or within 42 days of pregnancy PMSS Pregnant or within one year of pregnancy Ascertaining deaths: Temporal Boundaries

NVSS Underlying cause of death – parts I and II ICD-9 codes 630-676 Pregnancy check box Ascertaining deaths: Determiningthe Cause of death PMSS • Underlying cause of death – parts I and II • All other notes & information on death certificate • Matched live birth & fetal death certificates • Autopsy reports • Mat. mortality review committee reports • Pregnancy check box

Methods • PMSS received copies of death certificates for women of reproductive age from 50 States, DC, and New York City. PMSS used all available information to classify deaths as pregnancy-related. • We obtained the underlying cause of death (ICD-9 codes) for all pregnancy-related deaths in PMSS (1995-97) from NVSS by death certificate number • All Pregnancy-related deaths assigned ICD-9 codes 630-676 by NVSS were considered maternal deaths (Both PMSS & NVSS); those coded outside 630-676 by NVSS were not considered maternal deaths (PMSS Only) • Mortality files on the CDC Wonder System were used to ascertain information on maternal deaths in NVSS, and to calculate deaths reported only in NVSS (NVSS Only)

Analysis • Deaths in Both PMSS & NVSS, PMSS Only, and NVSS Only were analyzed by age group, race, region, cause of death, and time interval between pregnancy and death • Chi-square tests for statistical significance • Calculated a combined pregnancy mortality ratio

Deaths Reported in PMSS and NVSSUnited States 1995-97 n=1,471 deaths

Percent of pregnancy-related deaths (PMSS) coded as maternal deaths (ICD 630-676) by race and region P <0.003 P <0.001

Percent of pregnancy-related deaths (PMSS) coded as maternal deaths (ICD 630-676), by cause of death group P <0.0001

Distribution of all PMSS deaths by ICD-9 code and cause of death group

Percent of Deaths in PMSS & NVSS and PMSS only, by Interval Between Pregnancy and Death

Deaths Due to Pregnancy, United States 1995-97 • Maternal Mortality Rate 7.7*(NVSS) • Pregnancy-related Mortality Ratio 11.9* (PMSS) • Combined Pregnancy Mortality Ratio 12.6* (NVSS & PMSS) * Per 100,000 live births

ICD-10 and It’s Impact on Maternal Mortality • ICD-10 implemented beginning with US mortality data for 1999 • Changes in coding and selection rules • Large increase (39%) in the number of maternal deaths reported by NVSS between 1998 and 1999 • Addition of a pregnancy status question on the Revised US Standard Certificate of Death

Conclusions • Pregnancy-related deaths from hemorrhage, embolism, and hypertensive disorders of pregnancy are more likely to be classified as maternal deaths by NVSS than those due to infection or other medical conditions • Pregnancy-related deaths among Asian women and women in the West region are more likely to be classified as maternal deaths than those to women of other races and in other regions

Conclusions, cont’d • The difference in the inclusive time interval does not explain the disparity in rates between NVSS and PMSS • The combined sources of both systems provide an enhanced assessment of pregnancy mortality • It is anticipated that implementation of ICD-10 and the Revised US Standard Certificate of Death will decrease the disparity in the numbers of deaths due to pregnancy reported by NVSS and PMSS

An Assessment of Maternal Mortality in the United States, 1995-97