Fertility rates have declined in the U.S. and women are giving birth for the first time later and later, according to the Centers for Disease Control and Prevention.
The results came after researchers from the National Center for Health Statistics analyzed birth data compiled by the National Vital Statistics System from 2007 to 2017 that included breakdowns by race and geography.
The CDC defines "fertility rate" as "the total number of births in an area to the population of women most at risk of childbearing," typically women aged 15 through 44.
Total fertility rates fell both in rural and in urban settings. In rural counties, rates declined 12 percent, in small or medium metro counties, rates fell 16 percent and major metros saw a drop of 18 percent.
In 2007, rural rates were about 5 percent higher than in metro counties, a difference that increased to 14 percent by 2017, the data showed. Rural rates in 2017 were about 10 percent higher than more medium-sized areas.
When comparing different ethnic groups, the researchers found the largest decrease among Hispanic women -- rates fell 26 percent in rural areas, 29 percent in medium-sized areas and 30 percent in big cities.
The average age of new mothers in rural areas increased to 24.5 years from 23.2, while in medium-sized regions it rose to 25.8 years from 24.3 and in major metros it climbed to 27.7 years from 25.9.
Non-Hispanic black mothers in large metros experienced the largest increase in age among different ethnicities -- a rise to 25.6 years from 23.2 years.
Dr. Anna Jackson is a resident of psychiatry at Vanderbilt University and a member of the ABC News Medical Unit.