Age-adjusted infant mortality dropped 11% from 2000 to 2017 in the United States, but the even larger decline for infants born to black women still left a death rate more than twice as high as those of white or Hispanic infants, according to a new analysis from the National Center for Health Statistics.
while the crude mortality rate fell 16% from 6.89 to 5.79, reported Anne K. Driscoll, PhD, and Danielle M. Ely, PhD, of the NCHS.
Over that same time period, age-adjusted infant mortality for births to black women went from 13.59 per 1,000 to 11.19, a drop of 18%. By comparison, age-adjusted mortality declined 7% from 5.59 per 1,000 for infants born to Hispanic women to 5.21 in 2017, they said in a National Vital Statistics Report.
Changes in maternal age distribution had an important effect on infant mortality. Women aged under 25 years, who have higher mortality rates, were less likely to give birth in 2017 than in 2000, and women aged 30-39 years, who have the lowest rates, made up a larger share of births in 2017, they pointed out.
It was, however, changes in age-specific mortality rates (ASMRs) that had the largest influence on the overall drop in the crude mortality rate, accounting for about two-thirds of the overall decline, the NCHS researchers said, noting that the effect varied by race and Hispanic origin.
Births to non-Hispanic white women mirrored the national situation: Approximately two-thirds (68.7%) of the decrease in infant mortality came from changes in ASMRs and one-third (31.3%) from changes in maternal age distribution. Among non-Hispanic black women, the distribution was 95.2% ASMRs and 4.8% age distribution, Dr. Driscoll and Dr. Ely reported based on data from the National Vital Statistics System.
The disparity between the two trends went even further for infants born to Hispanic women. Changes in ASMRs were responsible for 133.7% of the overall change in crude mortality versus –33.7% for changes in maternal age distribution. “If no changes occurred in the ASMRs, the changes in the maternal age distribution would have resulted in a higher mortality rate in 2017,” they explained.
The declines in the ASMRs may be related to incremental improved survival of preterm and low-birthweight infants in certain groups. “While little or no progress has been made to lower [these] two key risk factors for poor birth outcomes, progress has been made in lowering the mortality rates of at-risk infants across maternal age and race and Hispanic origin, resulting in lower ASMRs for all age groups,” the investigators suggested.
It also is possible that “changes in other factors, such as maternal education and cigarette smoking during pregnancy, may have indirectly resulted in declining ASMRs for all age groups over time,” they added.
SOURCE: Driscoll AK, Ely DM. National Vital Statistics Reports. 2020;69(5):1-18.