Maternal Mortality Surveillance, 1974-1978

Andrew M. Kaunitz, M.D. Roger W. Rochat, M.D. Joyce M. Hughes Jack C. Smith, M.S. David A. Grimes, M.D. Division of Reproductive Health Center for Health Promotion and Education Introduction

Surveillance of maternal deaths has several goals, including: identifying risk factors associated with maternal deaths, tracing patterns of these risk factors over time, and providing a benchmark to which the safety of fertility control measures can be compared. This report outlines the program currently being conducted by CDC's Division of Reproductive Health in an effort to achieve these goals. Materials and Methods

CDC obtained copies of 1974-1978 death certificates from each state health department for all deaths classified by the National Center for Health Statistics (NCHS) as maternal (1,949), and for any additional pregnancy-related deaths (741) identified by state health departments.

National maternal mortality data published by NCHS for 1974-1978 were based on the Eighth Revision of the International Classification of Diseases, Adapted (ICDA-8) (1). To classify the maternal deaths in this report, we used the ninth revision of the International Classification of Diseases (ICD-9) (2), which has a broader definition of maternal death than ICDA-8. The ICD-9 definition includes as maternal:

the death of any woman while pregnant or within 42 days of termination of pregnancy,* from any cause related to or aggravated by the pregnancy or its management but not from accidental or incidental causes. (3) *Includes live births, stillbirths, abortions, and ectopic pregnancies.

Pregnancy-associated deaths from underlying conditions aggravated by the pregnancy (e.g., diabetes, heart disease or tuberculosis), which would not be coded as maternal using ICDA-8, are coded as maternal when ICD-9 is used. We excluded 206 deaths from causes incidental to pregnancy (e.g., motor vehicle accidents).

The traditional measure of maternal mortality is maternal deaths/100,000 live births; this measure is known as the "maternal mortality rate." The live-birth data used to calculate rates were provided by NCHS. Results

For the years 1974-1978, we classified 2,555 deaths as maternal. For this 5-year period, the maternal mortality rate was 15.8/100,000 live births (Table 1). While the annual number of live births was relatively stable over this period, the maternal mortality rate declined by 27%, from 18.5 in 1974 to 13.5 in 1978.

With the exception of the youngest age group (less than 15), maternal mortality rates increased with maternal age (Table 2). The maternal mortality rate for women ages 35-39, for instance, was some five times higher than that for women ages 15-19.

Race was an important risk factor for maternal death. The 1974-1978 maternal death rate for blacks and others (36.4) was more than three times higher than the rate for whites (11.0) (Table 3). Discussion

Maternal death rates in the United States have declined over thirtyfold since 1940 (4). A number of factors may have played a role in this decline, including greater access to and utilization of prenatal care and hospitals for childbirth; technical advances in medical care such as improvements in blood banking, antibiotic treatment of infections, and anesthesia; lower parity; fewer unwanted births; and the decrease in the number of illegal abortions (5). In addition, the reduction in births to women over age 35 (6), achieved in part through increased surgical sterilization (7), may have contributed to lower maternal mortality rates.

The number of maternal deaths included in this report is 21% higher than the number published by NCHS in national vital statistics reports for the same period. A large part of this difference results from our use of the broader ICD-9 definition of maternal death (8). However, even using the broader definition, we may be substantially undercounting the number of maternal deaths in the United States. Intensive surveillance of maternal deaths in Georgia (9) and New Jersey (10) suggests that there has been substantial failure to identify and classify maternal deaths properly, principally through failure to indicate on the death certificate the temporal or causal relationship of the pregnancy.

The maternal mortality rate for women of black and other races is substantially higher than for white women, as is the death-to-case rate for legal abortion (11) and ectopic pregnancy (12). Less access to, and utilization of, obstetric care by minority race women (13) may account in part for these higher rates.

Marital status, parity, and preexisting health problems may also influence risk of maternal mortality, but because national data on these factors are not available, we have not calculated maternal mortality rates by these variables.

Although maternal mortality has declined, 75% of maternal deaths are still considered preventable (14), suggesting that further decreases are feasible. Increased access to and utilization of family planning and prenatal services, particularly by minority women, might reduce overall maternal mortality rates (15) as well as the differential between the maternal mortality rates for whites and for blacks and others. Improved management of pregnancy complications could further reduce rates of maternal death (15). These observations suggest that obstetric care should be targeted to minority women, and that existing medical technology, if appropriately applied, can prevent most maternal deaths in the United States.

This analysis of maternal mortality has important implications for national health objectives (16). One of these objectives is to reduce the maternal mortality rate to 5/100,000 live births by 1990. The benchmark for this goal was a reported maternal mortality rate of 9.6 for 1978. Our analysis shows a maternal mortality rate of 13.5 for that year, 41% higher than the benchmark. In view of this, increased efforts may be required to achieve the stated objective.

References

1. National Center for Health Statistics. International classification of diseases for use in the United States. 8th Revision. Washington, D.C.: U.S. Government Printing Office, 1967.

2. Commission on Professional and Hospital Activities: The international classification of diseases, 9th Revision, Clinical Modification. Ann Arbor: Edwards Brothers, Inc., 1978.

3. National Center for Health Statistics. Vital Statistics. Instructions for classifying the underlying cause of death, 1981. Instruction Manual, Part 2a. Hyattsville, Md: National Center for Health Statistics, 1980.

4. Rochat RW. Maternal and perinatal statistics. In: Aladjem S, ed. Obstetrical practice. St. Louis: CV Mosby Co., 1980:264-78.

5. Centers for Disease Control. Abortion Surveillance, 1979-1980. In: CDC Surveillance Summaries (published four times a year). 1983;32(No. 2SS):1SS-7SS.

6. National Center for Health Statistics. Trends in fertility in the United States. Hyattsville, Md.: National Center for Health Statistics, 1977. (Vital and health statistics. Series 21: Data from the National Vital Statistics System.) (DHEW Publication No. ÕHRAå 778-1906).

7. Centers for Disease Control. Surgical Sterilization Surveillance Report, 1979-1980. September 1983.

8. Smith JC, Hughes JM, Pekow PS, Rochat RW. An assessment of the incidence of maternal mortality in the U.S. Am J Public Health (in press).

9. Rubin GW, McCarthy B, Shelton J, Rochat RW, Terry J. The risk of childbearing re-evaluated. Am J Public Health 1981;71:712-6.

10. Ziskin LZ, Gregory M, Kreitzer M. Improved surveillance of maternal deaths. Int J Gynecol Obstet 1979;16:281-6.

11. LeBolt SA, Grimes DA, Cates W. Mortality from abortion and childbirth, are the populations comparable? JAMA 1982;248:188-91.

12. Dorfman SF. Deaths from ectopic pregnancy, United States, 1979-1980. Obstet Gynecol 1983;62:334-8.

13. Greenberg RS. The impact of prenatal care in different social groups. Am J Obstet Gynecol 1983;145:797-801.

14. Schaffner W, Federspiel CF, Fulton ML, Gilbert DG, Stevenson LB. Maternal mortality in Michigan: an epidemiologic analysis 1950-1971. Am J Public Health 1977;67:821-9.

15. Gibbs CE, Locke WE. Maternal deaths in Texas,1969 to 1973. Am J Obstet Gynecol 1976;126:687-92.

16. Public Health Service. Promoting health/preventing disease: objectives for the nation. Washington, D.C. U.S. Government Printing Office, 1980.

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