The US birth rate has fallen to the lowest in 35 years, and experts worry we could face a 'demographic time bomb'

• There's been a steady decline in births in the US, and 2019 recorded the fewest number of births in 35 years.
• Experts have warned the trend could lead to a "demographic time bomb."
• The coronavirus could also impact birth rates in 2020, with some people choosing not to get pregnant and others unable to due to the halt on some fertility treatments.

Fewer babies were born in the US in 2019 than in any of the 35 years before, continuing a trend some experts have warned could lead to a "demographic time bomb," or when fertility rates decrease as longevity increases.

The preliminary report out of the Centers for Disease Control and Prevention found that there were about 3.7 million births in the US in 2018, a 1% drop from 2018.

Broken down further, births among teenage moms were markedly down (5% among 15- to 19-year-olds), and women in their 20s were also less likely to give birth in 2019. Rates among 35- to 39-year-old women remained steady.

For women over 40, though, birth rates were up about 2%, maintaining a theme also seen since 1935.

Experts say the ongoing "baby bust" seems to be mostly attributable to changing attitudes toward parenthood that are leading more people delay childbearing and have fewer children once they start, if they have children at all.

According to gynecologist Dr. Eve Feinberg, declining birth rates are also influenced by misinformation about how fertility works.

"People overestimate the success of fertility treatment," Dr. Feinberg previously told Insider. "While it is successful, it has limitations at older ages."

This year's report report also found the cesarean delivery rate dropped to under 32%, and the number of preterm births rose for the fifth year in a row, to more than 10%.

Experts have warned of a 'demographic time bomb'

Some of the CDC report is positive: Mainly, that teen pregnancies and births are significantly down once again. Between 2017 and 2018, for example, the birth rate among 15- to 19-year-old decreased 7% and in this last year it decreased another 5%.

But the overall trend has troubled some experts who say the United States could suffer a demographic time bomb in which there eventually aren't enough young people to support both the economy and older people who continue to live longer.

At its most extreme, Insider previously reported, demographic time bombs could lead to the eventual extinction of a country's population.

It's unclear how the coronavirus pandemic will affect 2020 birth rates

While celebrities appear to be enjoying a baby boom, the coronavirus pandemic could have the opposite affect on the population at large. Many people who need medical help to get pregnant have needed to delay their fertility treatments. Some may not resume their care or may find it's too late once they're ready or able.

Other couples are holding off on conceiving naturally because so much remains unknown about how the virus affects pregnant women and their future children.

But the coronavirus's effect on birth control and abortion access could outweigh these changes. Only time will tell.

"The decline due to COVID-19 might be different given the extent and severity of the crisis, and the long-lasting uncertainty that is caused by it," Hans-Peter Kohler, a University of Pennsylvania fertility researcher, told AP.