America’s preterm birth rate — those born before 37 weeks gestation — rose 12% between 2014 and 2022, to 8.67%. That means more than 1 in 12 babies are delivered prematurely, although most premature births are born closer to full term, on the later side of prematurity.
And 20% are born in what’s called “early term,” the period at 37 to 38 weeks gestation, which is just shy of being a full-term birth.
That’s according to a new report from the National Center for Health Statistics at the Centers for Disease Control and Prevention. The report says early preterm birth occurs at less than 34 weeks, while late preterm birth is 34 to 36 weeks. Early term is 37 to 38 weeks; full term is 39 to 40 weeks.
The analysis only considered singleton births, since twins, triplets and other multiple births are typically delivered earlier than full term.
“Gestational age is a strong predictor of short- and long-term morbidity and early mortality,” the authors wrote. “Births delivered preterm are at the greatest risk of adverse outcomes, but risk is also elevated for early-term compared with full-term births.”
The report said that maternal age often plays a role in premature delivery. It notes that preterm birth rates increased for each 10-year maternal age group in that time frame, ranging from 9% in the group aged 20 and younger to 16% among those 40 and older.
The share born in the early preterm age ranged from 3% among those 20-29 and those 40 and older, while the share was 6% among those 30-39. Late preterm birth increases ranged from 11% to 21%.
Black mothers were nearly twice as likely to give birth before babies reached term, compared to white mothers (12.5% vs. 7.6%). And after age 40, compared to ages 20-29, the risk of preterm birth was 12.5% vs. 8.23%.
Health and other risks of prematurity
The report said that “gestational age is a strong predictor of short- and long-term morbidity and early mortality. Births delivered preterm are at the greatest risk of adverse outcomes, but risk is also elevated for early-term compared with full-term births. This report demonstrates a shift from 2014 through 2022 across gestational age categories, with the largest changes occurring among early-term births — particularly those delivered at 37 weeks — and among late- and post-term births. Similar shifts were observed across the maternal age and race and Hispanic-origin groups studied.”
Among the possible adverse risks of premature birth are breathing problems, difficulty feeding, cerebral palsy, developmental delay, and hearing and vision problems, according to the CDC.
March of Dimes adds that premature birth can create long-term intellectual and developmental disabilities for babies, who may struggle with physical development, learning, communication, self-care and getting along with others.
Dr. Céline Gounder, a CBS News medical contributor and editor-at-large for public health at KFF Health News, told “CBS Mornings” that the rise in early births is worrisome.
“If a baby is born early term, not preterm but even early term, there can be complications,” she said. “The lungs may not be fully developed, that baby may not be able to regulate their temperature or their blood sugar as well. They may not have that suckling reflex that allows the baby to feed, and so that means staying in the hospital for longer so the baby has a support to survive,” she said in an interview quoted by CBS News.
The mother’s age, obesity, high blood pressure and diabetes are among factors that increase the risk of delivering a baby early, she said.
Detecting pregnancy changes
Unrelated to the preterm birth report, a new study found that a strap that tracks the heart rate of a pregnant woman may detect changes that can lead to preterm birth.
Using data from the WHOOP brand heart tracker, a West Virginia University researcher and a WHOOP employee, along with their colleagues, used tracker data from 241 pregnant people ages 23 to 47 to analyze heart rate variations, according to New Scientist.
The babies were all singletons born between March 2021 and October 2022.
As in previous research, those who delivered at full term had a clear heart rate variability switch at about 33 weeks of gestation, with a steady pulse increase thereafter until birth. But for those who delivered prematurely, the patterns were “far less consistent.”
The researchers suggest that monitoring the heart rate might provide a clue as to how the pregnancy is progressing and offer clues to whether more care should be provided to prevent premature delivery.