"Infertility rates have come down a little bit," says Dr. Anjani Chandra, researcher at the NCHS, part of the Centers for Disease Control and Prevention. "That surprises people because they think it is going up. In fact, it really hasn't been the case."
Chandra and colleagues looked at data from the National Survey on Family Growth, in which more than 22,000 people were interviewed face to face between 2006 and 2010. The survey was also done in 1982 and 2002.
The surveys showed that 8.5 percent of married women aged 15 to 44 were infertile in 1982 – defined as having been married and having unprotected sex for 12 months without becoming pregnant. This fell to 6 percent of the same age group, married or unmarried, in 2006-2010.
When they added in women who could finally get pregnant but who miscarried before giving birth, the number rose to 11 percent
"Contrary to popular perceptions based on infertility service use and media coverage about biological clocks, we still don't see that," Chandra told NBC News.
It hasn't changed for men, either.
"Some form of infertility ... was reported by 9.4 percent of men aged 15–44 and 12 percent of men aged 25–44 in 2006–2010, similar to levels seen in 2002," Chandra's team writes in the report.
One obvious answer would seem to be increased use of fertility treatments. Since 1982, in vitro fertilization or IVF has been perfected, and more than 163,000 treatments were done in 2011 – just about double the number done a decade before. Federal law requires doctors and clinics to report fertility treatments and success rates to the CDC.
But this data doesn't show whether 163,000 separate people were treated, and the new statistics suggest that in fact more people aren't being treated. Instead, individuals may be undergoing more treatments in the same year, says Chandra.
That's because the percentage of women who have ever gotten fertility services was the same in 2006-2010 as compared to 2002 – 11.9 percent in both times.
Dr. Richard Reindollar of the American Society for Reproductive Medicine said the findings were encouraging.
"Even though the ages at which women in the United States have their children have been increasing since 1995, the percentage of the population suffering from infertility or impaired fecundity has not increased," Reindollar said in a statement.
Image: Fertility lab, via Shutterstock