The United States recorded the most deaths in its history and the fewest births since 1998, resulting in the lowest population gain from natural causes in 35 years, an analysis of 2013 Census Bureau estimates released Thursday shows.

Americans remain cautious about having babies following the worst recession since the Great Depression, although they are increasingly changing homes again, suggesting growing confidence in the economic recovery.

Those are among the findings from county-level data that also show the largest metropolitan areas are getting bigger as much of the rest of the nation sees slower population growth or declines. Rural areas where oil and natural gas production is booming and Gulf Coast retirement conclaves are notable exceptions to that trend.

"The recession's influence on migration may be waning, but it continues to have a negative impact on births," said Ken Johnson, a senior demographer with the University of New Hampshire's Carsey Institute who analyzed the data.

If the nation returned to a more normal fertility rate, it could boost the economy by spurring demand for new homes and goods. Rising fertility rates in states such as South Dakota, where unemployment is 3.6 percent, have prompted some demographers and economists to predict a reversal of the nationwide decline in fertility that coincided with the recession and its aftermath.

Johnson's analysis is based on newly released data for the year ending July 1, 2013. It shows there were 3.95 million births during those 12 months, compared with 4.31 million in the pre-recession 2006-07 period, a drop of 8.4 percent amid an overall U.S. population that continued to grow because of immigration.

Delaying motherhood

The preliminary U.S. fertility rate for the 12-month period ending June 2013 was 62.7 births per 1,000 women ages 15-44, according to the National Center for Health Statistics. That was down from the recent-history high of 69.3 in 2007, and slightly down from the year ending June 30, 2012.

"These data suggest that the impact of the recession has been particularly pronounced among younger women, who are likely delaying" becoming mothers, Johnson said.

The recession lasted from December 2007 to June 2009.

States that did better during the recession had no or little fertility declines, while harder-hit areas such as Arizona, Nevada, California, Florida and Georgia posted some of the biggest drops, the National Center for Health Statistics data showed.

Metropolitan areas with populations of 1 million or more grew 1 percent during the year that ended July 1, 2013, the Census Bureau said. Those with populations under 250,000 recorded half that rate of growth.

The nation's metro areas contained 269.9 million people in 2013, up about 2.3 million from 2012, the Census Bureau said.

In raw numbers, the Houston metropolitan area added the most people during the year, with estimated growth of 137,692, or 2.2 percent. That was followed by the New York City area, which added an estimated 111,749 people, or 0.6 percent.

The fastest-growing metro area during the year ending last July was a central Florida area called The Villages that's among the world's largest retirement communities. It saw an estimated population increase of 5.2 percent, growing to 107,056.

Exurbs pulling out of slump

Remote towns and distant "exurbs" on the fringes of metropolitan areas may also slowly be starting to pull out of their recession-related slump, the data show.

The nation's exurbs displayed signs of slow growth, according to an analysis by William Frey, demographer at the Brookings Institution.

Urban areas and closer-in suburbs still had faster growth than exurbs as workers avoided the economic risks associated with selling homes or looking for new jobs.

Exurbs as a whole grew 0.57 percent during the year ending last July, while urban areas grew 0.81 percent and mature and emerging suburbs recorded a rate almost twice of the exurbs, Frey's analysis shows. That still was an increase for the exurbs, which had growth of 0.35 in 2010-11 and 2011-12.

Areas rich with oil and natural gas in and near the Great Plains continue to record some of the fastest population growth as workers are drawn to jobs there, the Census Bureau said.

Of the nation's 10 fastest-growing metropolitan statistical areas, six were within or near the Great Plains: Odessa, Austin and Midland, Texas; Fargo and Bismarck, N.D.; and Casper, Wyo.

"When the economy is slow, people will go where there are jobs," Frey said.

Seven of the 10 fastest-growing "micropolitan" statistical areas, which contain an urban cluster of between 10,000 and 49,999 people, were in or adjacent to the Great Plains.