(CNN) US birthrates hit "another record low" in 2017, according to a report released Thursday by the National Center for Health Statistics.
The report estimates that 3,853,472 babies were born nationally last year -- the fewest in 30 years and down from a 2007 record high of 4,316,233.
The total fertility rate in 2017 was "below replacement -- the level at which a given generation can replace itself" when deaths are also taken into account, the report says, also noting that this has generally been the case since 1971.
"There are experts out there who would argue that, given limited resources, maybe there's an advantage to lower population growth, which could be driven by fewer births," said Gretchen Livingston, a senior researcher at Pew Research Center who has analyzed these data for years but was not involved in the new report. "But on the other hand, there's a lot of people out there who think that maybe lower fertility might prove problematic, particularly as the labor force starts to shrink as a result."
Birthrates were down for women of all ages -- except those in their early 40s. Experts say that women choosing to have children later in life is lowering birthrates, and this change might be temporary.
"Clearly, there is postponement," Livingston said. "Now, will all the women who've been postponing birth ... ultimately catch up on their fertility? I'm not sure."
The teen birthrate, defined as those between the ages of 15 and 19, also continued to decline: It was 7% less than the year prior, down to 194,284 total births. This number is less than half of the 444,899 babies born to teens in 2007.
Experts have described this decline as "phenomenal," as did Dr. Elise Berlan, a physician in the section of adolescent medicine at Nationwide Children's Hospital, who was not involved in this research.
"We know that the vast majority of teen births are unintended," Berland previously told CNN, adding that "access to contraceptives and use of contraceptives ... has really led to these kind of changes."
Separate data have also showed a decrease in teens' reported sexual activity in recent years.
A number of short-term influences may be contributing to the decline, including the late-2000s economic recession, experts say.
"Our own survey data shows that people stated they were postponing birth until the economy picked up again," Livingston said. "Whenever there's an economic downturn, it's pretty normal for there to also be a downturn in fertility."
But in the long term, there is a broader set of drivers behind the numbers, including more women in the work force, higher levels of education and postponement of marriage, she said.
"Even though there's so much discussion about birth outside of marriage, the fact is that someone who is married is still a lot more likely to have a baby than someone who's not married."