That success rate was only slightly lower than in women who also reported trouble conceiving and opted for treatment with fertility hormones or in vitro fertilization (IVF).

"Many women aged up to 36 years with a history of infertility can achieve spontaneous conception and live birth without using fertility treatment indicating (they) are sub-fertile rather than infertile," study researcher Danielle Herbert of the University of Queensland School of Population Health in Brisbane told Reuters Health in an email.

That means that if nothing is clearly wrong -- men make enough sperm, and women are ovulating regularly -- couples who have had trouble conceiving should still be optimistic they can get pregnant on their own, researchers said.

"I'm not surprised that women who were not treated still get pregnant -- we know that," said Dr. Courtney Lynch, head of reproductive epidemiology at The Ohio State University in Columbus, who wasn't involved in the new research.

"We know we can get women pregnant quicker if we have them go into IVF, but if we give women time, (many of them) can still get pregnant," she told Reuters Health.

The research is part of a long-term study of more than 7,000 women living in Australia. Starting in 1996, participants filled out health surveys every few years, which included questions on pregnancy and childbirth.

The current data is from about 1,400 women age 28 to 36 who reported on the most recent questionnaires that they'd tried unsuccessfully to get pregnant for at least a year at a time.

Close to 600 of those women said they'd received infertility treatment using IVF or fertility hormones, including Clomid.

Through the latest survey in 2009, 53 percent of those women said they had a baby following fertility treatment, compared to 44 percent of women who'd had trouble conceiving but didn't seek treatment, the researchers reported in the journal Fertility and Sterility.

For women who did have a baby, there was no difference in pregnancy complications -- including stillbirths or premature births -- between those who did and didn't get fertility treatment.

AFTER A YEAR, GET CHECKED OUT

Herbert and her colleagues pointed out some limitations of the report, including that they didn't know if women changed male partners at any point during the study period, which could have affected their chances of becoming pregnant.

And one fertility researcher not involved in the new study said it's impossible to know whether women who didn't get treatment lost or gained weight, or changed their diet and lifestyle to improve their chances of becoming pregnant.

Alice Domar, of Boston IVF, said that the number of women who got pregnant without treatment after a year of infertility is higher than previous studies have suggested.

"What a lot of physicians feel is if you're not pregnant within a year, it usually means there's something going on," she told Reuters Health.

Domar said that she'd still recommend a woman who's been trying to get pregnant for that long get checked out to see if there's anything preventing her from conceiving. If not, she can keep trying. But if, for example, her tubes are blocked, any extra waiting is "time out the window," she said.

Lynch said that about 15 percent of women won't get pregnant after a year of trying, but only three to five percent of them are truly infertile. The rest will likely conceive on their own after another year or two.

"There are a lot of patients that don't want to wait another year, especially if you're an older patient," Lynch said -- and they might want fertility treatment, even if pregnancy without it may be possible.

"But if you're 28, I think waiting another year makes sense potentially before going on a treatment."

According to Domar, most women who can't get pregnant will only need treatment with fertility hormones, which cost about a dollar a day, to get ovulation back to normal. IVF, on the other hand, runs for about $15,000 a cycle, and may or may not be covered by insurance.

'WOMEN SHOULD STILL BE HOPEFUL'

The findings can be seen as encouraging for some women, Domar said.

"It means if you've been trying for a year and you're young and you have unexplained infertility, according to this data you have a decent chance of spontaneously conceiving," Domar said.

Dr. Sacha Krieg, an ob-gyn who studies recurrent pregnancy loss at the University of Kansas Medical Center in Kansas City, agreed.

"Women should still be hopeful that they're going to get pregnant, even if they've been trying for an entire year," she said.

Still, Krieg told Reuters Health, "I wouldn't want this to (dissuade) women from seeing a fertility specialist and being evaluated."

SOURCE: bit.ly/xbeB1L Fertility and Sterility, online January 23, 2012.

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