A final tally of babies born in the U.S. last year confirms that the birth rate fell again in 2018, reaching the lowest level in more than three decades.

The report from the Centers for Disease Control and Prevention's National Center for Health Statistics finds there were 3,791,712 births registered in the U.S. in 2018, down 2 percent from 2017.

A closer look at the data suggests that Americans are not having enough babies to sustain the population.

The total fertility rate for 2018 was 1,729.5 births per 1,000 women aged 15 to 44. (The fertility rate refers to how many children women have overall; birth rate refers to how many children women have in a single year.) But in order for the nation to reproduce its population and remain stable, the CDC says there would need to be 2,100 births per 1,000 women.

That means each woman needs to have at least two babies to replace fathers and mothers, as well as account for extra deaths.

The data also show that women are waiting longer to have children. Birth rates among women in their 20s and early 30s declined, but they started to increase slightly among women 35 to 44.

The teen birth rate, for girls between the ages of 15 and 19, fell 7 percent, from 18.8 births per 1,000 women in 2017 to 17.4 births per 1,000 in 2018.

Fewer babies are being born to smoking mothers. Of the women who gave birth in 2018, 6.5 percent reported using a tobacco product, a 6 percent decline from 2017. The downward trend was noted among white women, black women and Hispanic women.

And fewer babies are being born via cesarean section. The c-section delivery rate fell slightly in 2018 to 31.9 percent, from 32 percent the year before.

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