By NICHOLAS BAKALAR
A baby being cared for in a neonatal intensive care unit. The preterm birthrate in the United States in 2016 increased to 9.84 percent from 9.63 percent in 2015. Credit Marice Cohn Band/The Miami Herald, via Associated Press
In 2016, the fertility rate in the United States was the lowest it has ever been.
There were 62 births per 1,000 women aged 15 to 44, down 1 percent from 2015. There were 3,941,109 babies born in 2016.
In an analysis issued by the National Center for Health Statistics, researchers report that birthrates declined to record lows in all groups under age 30. Among women ages 20 to 24, the decline was 4 percent. For women 25 to 29, the rate fell 2 percent.
The decrease in the birthrate among teenagers — 9 percent from 2015 to 2016 — continues a long-term decline: 67 percent since 1991.
“The decline in teens is across the board,” said the lead author, Brady E. Hamilton, a statistician and demographer with the center. “Younger teens, older teens, and across all racial and ethnic groups.”
The present overall fertility rate puts the United States population below replacement level, but that does not mean the population is declining.
“Yes, it’s below replacement level, but not dramatically so,” Dr. Brady said. “We have a high level of influx of immigrants that compensates for it.”
Fertility increased among older women. The birthrate for women ages 30 to 34 rose by 1 percent over the 2015 rate, and the rate for women ages 35 to 39 went up by 2 percent, the highest rate in that age group since 1962.
Women ages 40 to 44 also had more babies, up 4 percent from 2015. The rate for women 45 to 49 increased to 0.9 births per thousand from 0.8 in 2015.
The birthrate among unmarried women went down, to 42.1 per 1,000 from 43.5 in 2015, a drop of 3 percent and the eighth consecutive year of decline since the peak of 51.8 in 2007 and 2008.
There were differences by race: 28.4 percent of white babies had unmarried parents, 69.7 percent of black babies and 52.5 percent of Hispanics.
The preterm birthrate — babies born before 37 weeks of gestation — increased to 9.84 percent from 9.63 percent in 2015. This is the second year in a row of increases in preterm birth after a decline of 8 percent from 2007 to 2014.
The highest rate of preterm birth was among non-Hispanic blacks, at 13.75 percent, and lowest among Asians, at 8.63 percent.
In 2016, 31.9 percent of births were by cesarean section, compared with 32 percent in 2015.