Infertility "decreased slightly but significantly, from 8.5 percent of married women to 6 percent of married women," between 1982 and 2010, said study author Anjani Chandra.
Looked at another way, nearly 2.4 million women had problems with infertility in 1982, compared with 1.53 million in 2010, she said.
Many people may think that difficulties getting pregnant are increasing because of the greater use of in fertility treatments and in vitro fertilization (IVF), "but that's just not shown in the data," said Chandra, a research scientist with the U.S. National Center for Health Statistics, part of the Centers for Disease Control and Prevention.
Chandra noted that many women are having children later in life than in past decades, which may involve fertility issues or delays. But the rate of infertility among older women has not increased, she said.
The study also compared another measure of difficulty in having a child, known as "impaired fecundity."
"Contrary to public opinion, infertility and impaired fecundity are not on the rise among women of reproductive age in the United States," said Chandra.
Infertility is the inability of a woman to conceive after at least a year of unprotected sex with her husband or live-in partner. Fecundity describes the physical ability to get pregnant or carry a child to full term.
There is some overlap between infertility and impaired fecundity, but they're not the same.
"Impaired fecundity among married women and among all women 15 to 44 showed a significant increase in 2002 (relative to earlier years), but has fallen back to levels seen in the earlier years," Chandra said.
Because many baby boomers delayed childbirth and took advantage of fertility treatments, there was a perception that this older, more educated and wealthier group of mostly white women were suffering from fertility problems, she noted.
Among married women in 2006-2010, black women were more likely to be infertile than white women, the study found.
But educational, racial or socioeconomic differences in themselves didn't have that much impact, Chandra said.
"Where the racial and economic differential comes in is in the use of medical services -- it's a health care disparity," she said.
Dr. Jennifer Wu, an obstetrician and gynecologist at Lenox Hill Hospital in New York City, said that "IVF and fertility are more present every day in conversation and the media, so people feel it's a big problem -- everybody is having IVF."
The only difference in fertility is age, she said. "You might need more help at 44 than if you are 24," Wu added.
Wu noted that women can spend thousands of dollars on fertility treatments. For example, a single IVF treatment can run $20,000 and many women have several before they become pregnant, she said.
Among men, some form of infertility was reported by 9.4 percent of those aged 15 to 44 and by 12 percent of those aged 25 to 44 in 2006-2010, similar to earlier rates.
The report relied on data from a nationwide survey made up of more than 22,000 interviews with U.S. men and women.
To learn more about infertility, visit the U.S. Centers for Disease Control and Prevention.