(HealthDay)—Most of the decline in infant mortality rates from 2000 to 2017 was due to declines in rates across maternal age groups, according to the June 25 National Vital Statistics Reports, a publication from the U.S. Centers for Disease Control and Prevention.

Anne K. Driscoll, Ph.D., and Danielle M. Ely, Ph.D., from the National Centers for Health Statistics in Hyattsville, Maryland, used 2000 to 2017 linked birth and infant death data to examine the contribution of changing maternal age distribution and maternal age-specific rates on overall infant mortality rates.

The researchers found that the age of women giving birth increased as infant mortality decreased during 2000 to 2017, although the decrease was uneven across maternal age groups. In 2017, the maternal age-adjusted was 6.13 compared with the crude rate of 5.79. Overall, 31.3 percent of the decrease in infant mortality rates for all births and for births to non-Hispanic white women and 4.8 percent of the decline in births to non-Hispanic black women were accounted for by changes in maternal age distribution. The remainder of the decline for these groups and for all of the decline in births for Hispanic women was due to declines in age-specific mortality rates.

"While the age distributions of women giving birth have changed during 2000 to 2017, particularly the decline in the percentages of births to teenagers, most of the decline in infant mortality rates is due to declines in rates across maternal age groups," the authors write.

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