May 15 (UPI) -- The U.S. birth rate dropped 2 percent from 2018 to 2017, hitting a 32-year low, the Centers for Disease Control and Prevention's National Center for Health Statistics reported Wednesday.
There were 3.7 million births in 2018 while the general fertility rate was 59 births per 1,000 women ages 15 to 44, a record low for the country. It was the fourth year in a row in which the birth rate declined.
Birth rates declined for nearly all age groups under 35. Teen pregnancies are declining. Babies born to teenage parents were down 7 percent in 2017. Women in their late 30s and early 40s are the only demographic seeing a spike in birth rates.
The total fertility rate was below replacement, meaning a given generation can't replace itself. The rate has generally been below replacement since 1971.
"Long term, it means we're going to have an increasing proportion of older people," Columbia University Mailman School of Public Health professor John Rowe told NBC News. "All the projections about what percent of the population will be elderly in 5, 10, 20 years from now were made with the assumption that the birth rate would be stable."
The lower birth rate will "have a significant impact on the labor market," Lowe said.
Donna Strobino said more women are delaying marriage and childbirth until later in life.
"We're clearly in the throes of major social change with regard to women getting married and choosing to have children," Strobino said. "There's no question that part of the explanation for that is economic. It's very expensive to raise children these days. And in part it's social -- all the changes in women's roles."
But fertility declines with age and often couples wait too long, said Dr. Helen Kim, a professor at Northwestern University's Feinberg School of Medicine.
"Some have been married for more than 10 years before they think about having kids," Kim told NBC News. "There have been many advances in fertility treatment, but there is still no treatment for reproductive aging."