Fertility rates for white women were down in every US state in 2017 - below the rate needed for the population to replace itself, a new report from the Centers for Disease Control and Prevention (CDC) reveals.

However, among black and Hispanic women, fertility rates were up in 12 and 29 states, respectively.

When researchers looked at fertility rates for women of all age groups and races, they found that the nationwide rate was 16 percent lower than what is considered the level for a population to replace itself.

Experts say this is likely due to the fact that the large proportion of native-born women are having fewer children than before, while the much smaller proportion of immigrant-born women are having more children.

Additionally, the US white population has been hit hard by the Great Recession of 08-09, and is aging.

The overall fertility rate was only above the level in two states: South Dakota (with a boom in jobs for white Americans in the energy industry) and Utah (home to a high concentration of Mormons).

Demographers and public policy experts say if the rate continues to decline, there will not be enough healthy, young workers to keep the economy going and replace an aging population.

The highest total fertility rate was in South Dakota, 57 percent greater than the lowest rate in Washington, DC. But the nationwide fertility rate was 16 percent lower than what is considered the level for a population to replace itself

Researchers looked at the birth certificates from all 50 states, including the District of Columbia and self-reported data on the mother's race from the certificate.

The highest total fertility rate was found to be in South Dakota, which was 57 percent greater than the lowest rate in Washington, DC.

No state in 2017 had a total fertility rate for white women that was above the population replacement level - what the population needs to exactly replace itself from one generation to the next.

Meanwhile, black women had a rate higher than the population replacement level in 12 states and Hispanic women had a rate that was higher in 29 states.

However across all age groups and races, the total fertility rate for the US in 2017 was 1,765.5 per 1,000 women - 16 percent below the level of a population to replace itself.

There were only two states that had rates above the population level, South Dakota and Utah.

For Utah, the answer as to why is easy: its Mormon population.

'It's certainly from Mormonism,' Dr Kenneth Johnson, a professor of sociology at the University of New Hampshire, told DailyMail.com

'The concentration for so many Mormons in a state is why the fertility tends to be higher.'

Currently, nearly 63 percent of all Utahans identify as Mormon in comparison with two percent of the US population.

According to a 2014 Pew Research Center survey, Mormons were found to have more children than other US religious groups.

Mormons between ages 40 and 59 had an average of 3.4 children in their lifetime, compared to the national average of 2.1 among all Americans in that age range.

It's also the reason why Utah had the highest total fertility rate for white women in 2017.

As for South Dakota, Dr Johnson theorizes it's due to the state's economic growth.

Fertility rates for white women were down in every US state in 2017, the report revealed. The highest total fertility rate for white women was in Utah

Among black and Hispanic women, fertility rates were up in 12 and 29 states, respectively. Black women had the highest rate in Maine and Alabama had the highest rate for Hispanic women

'My guess is South Dakota has had so much growth in the energy industry, it may the influx of people to the state that affects fertility,' he said.

The US Bureau of Economic Analysis has reported strong earning growths for the Mount Rushmore State and, in 2018, South Dakota had the third-highest growth rate in the nation behind Washington and Utah.

In a bit of a surprising twist, Maine had the highest total fertility rate for black women in 2017.

Historically, Maine has been named the state with the largest white population - which is why many residents have nicknamed it the Wonder Bread State.

And, according to the Weldon Cooper Center for Public Service, Maine is expected to have in 2020 more residents aged 65 and older than resident aged 19 and younger.

'My guess is a lot of [the black women who've given birth to babies in Maine] are foreign born,' Dr Jonathan Resiman, an associate professor of economics and public policy at the University of Maine at Machias, told DailyMail.com.

'There's a significant Somali group in southern Maine, along the northern coast there's a lot of Central Americans. Immigrants who are foreign born tend to have higher fertility rates.'

Dr Philip Cohen, a professor of population at the Maryland Population Research Center, says the reason might also be that black populations are moving to places with majority white populations for economic prosperity.

'In places with with small black populations like Maine or Oregon, they may have had some positive reason for ending up there and are higher-educated and better off than black populations in inner cities,' he told DailyMail.com.

Also surprising, Alabama had the highest total fertility rates for Hispanic women in 2017, which Dr Cohen says might be because of immigration.

'Places like Alabama, Georgia, North Carolina might be new immigration destinations with more recent immigrants and immigrants have higher fertility rates,' he said.

One expert told DailyMail.com that the declining nationwide rates are an indicator that fertility rates haven't recovered since the Great Recession

Dr Johnson says the declining nationwide rates are an indicator that fertility rates haven't recovered since the Great Recession and wonders if they ever will.

'The question will be whether these numbers are temporarily low. Are these delayed or are they really going to be low forever and never going to return?' he said.

But Dr Cohen says he doesn't want people to be alarmed by the report.

'It might make people fear society will stagnate, but we're a couple of generations away from that,' he said.

'And there are pathways out of it. The main way is through immigration. It may be difficult with culture and politics, but not with demography.'

Dr Resiman agrees that immigrants are the key to replenishing population levels.

'We're not quite Japan yet,' he said, referencing the Asian's country struggling birth rates. 'But this definitely makes the case for why we need more immigrants.'