ATLANTA (AP) -- The economy may well be the best form of birth control.

U.S. births dropped for the third straight year -- especially for young mothers -- and experts think money worries are the reason.

A federal report released Thursday showed declines in the birth rate for all races and most age groups. Teens and women in their early 20s had the most dramatic dip, to the lowest rates since record-keeping began in the 1940s. Also, the rate of cesarean sections stopped going up for the first time since 1996.

Experts suspected the economy drove down birth rates in 2008 and 2009 as women put off having children. With the 2010 figures, suspicion has turned into certainty.

“I don’t think there’s any doubt now that it was the recession. It could not be anything else,” said Carl Haub, a demographer with the Population Reference Bureau, a Washington, D.C.-based research organization. He was not involved in the new report.

U.S. births hit an all-time high in 2007, at more than 4.3 million. Over the next two years, the number dropped to about 4.2 million and then about 4.1 million.

Last year, it was down to just over 4 million, according to the new report from the Centers for Disease Control and Prevention.

For teens, birth rates dropped 9 percent from 2009. For women in their early 20s, they fell 6 percent. For unmarried mothers, the drop was 4 percent.

Experts believe the downward trend is tied to the economy, which officially was in a recession from December 2007 until June 2009 and remains weak. The theory is that women with money worries -- especially younger women -- feel they can’t afford to start a family or add to it.

That‘s true of Mary Garrick, 27, an advertising executive in Columbus, Ohio. She and her husband, David, married in 2008 and hoped to start having children quickly, in part because men in his family have died in their 40s. But David, 33, was laid off that year from his nursing job and again last year.

He’s working again, but worries about the economy linger. “It kind of made us cautious about life decisions, like having a family. It‘s definitely something that affected us,” she said.

Kristi Elsberry, a married 27-year-old mother of two, had her tubes tied in 2009 after she had trouble finding a job and she and her husband grew worried about the financial burden of any additional children. “Kids are so expensive, especially in this day and age. And neither of us think anything’s going to get better,” said Elsberry, of Leland, North Carolina.

Many of the report’s findings are part of a trend and not surprising. There was a continued decline in the percentage of premature births at less than 37 weeks. And -- as in years past -- birth rates fell in younger women but rose a little in women 40 and older, who face a closing biological window for having children and may be more worried about that than the economy.

But a few of the findings did startle experts.

One involved a statistic called the total fertility rate. In essence, it tells how many children a woman can be expected to have if current birth rates continue. That figure was 1.9 children last year. In most years, it’s more like 2.1.

More striking was the change in the fertility rate for Hispanic women. The rate plummeted to 2.4 from nearly 3 children just a few years ago.

“Whoa!” said Haub, in reaction to the statistic.

The economy is no doubt affecting Hispanic mothers, too, but some young women who immigrated to the United States for jobs or other opportunities may have left, Haub said.

Another shocker: the C-section rate. It rose steadily from nearly 21 percent in 1996 to 32.9 percent in 2009, but dropped slightly to 32.8 last year.

Cesarean deliveries are sometimes medically necessary. But health officials have worried that many C-sections are done out of convenience or unwarranted caution, and in the 1980s set a goal of keeping the national rate at 15 percent.

It’s too soon to say the trend has reversed, said Joyce Martin, a CDC epidemiologist who co-authored the new report.

But the increase had slowed a bit in recent years, and assuming the decline was in elective C-sections, that’s good news, some experts said.

“It is quite gratifying,” said Carol Hogue, an Emory University professor of maternal and child health and epidemiology.

“There are strong winds pushing against C-sections,” she said, including new policies and education initiatives that discourage elective C-sections in mothers who have not reached full-term.

Hogue agreed that the economy seems to be the main reason for the birth declines. But she noted that it‘s possible that having fewer children is now more accepted and expected.

“Having one child may be becoming more `normal,’” she said.