Differences in Maternal Mortality Among Black and White Women—United States, 1990

The maternal mortality ratio is the number of maternal deaths per 100 000 live births. CDC's National Center for Health Statistics (NCHS) uses the term maternal mortality rate as required by the World Health Organization. In this report, the term "ratio" is used because the numerator includes some maternal deaths that were not related to live births, and thus were not included in the denominator. For this analysis, 3 years of data were combined to calculate maternal mortality ratios to promote statistical reliability and stability in the estimates. For example, 1990 ratios are based on data from 1989 through 1991. In addition, beginning with the 1989 data year, NCHS began using race of mother instead of race of child to tabulate live birth and fetal death data by race. In this analysis, race for live births is tabulated by the race of the child for maternal mortality to maintain comparability of ratios.

An underlying cause of death is defined by the International Classification of Diseases, Ninth Revision (ICD-9), as "(a) the disease or injury which initiated the train of morbid events leading directly to death, or (b) the circumstances of the accident or violence which produced the fatal injury." In 1979, the ICD-9 provided the first formal definition of maternal mortality, defining maternal death as the death of a woman while pregnant or within 42 days of termination of pregnancy. This definition differed from that used previously by NCHS, which included deaths up to 1 year after termination of pregnancy. However, the change from the 1-year limit used in the eighth revision to the 42-day limit used in the ninth revision did not greatly affect the comparability of maternal mortality statistics.4

The ICD code is revised approximately every 10 years. In the ninth revision, ectopic pregnancy (ICDA code 631) was transferred from complications of pregnancy (ICDA codes 630--634) to pregnancy with abortive outcomes (ICD codes 630-638).5 In this report, maternal deaths from ectopic pregnancy are included with abortive outcomes for all time periods.