In some instances from the research, the parents had had another child previously using in vitro fertilization (IVF) -- while in other cases the couple had a baby even after an unsuccessful experience with IVF.

"Most infertile couples think that they are unable to conceive spontaneously whereas our study shows (this) remains possible," Dr. Pénélope Troude at the French national medical research institute, INSERM, wrote in an email to Reuters Health.

"Our results should give hope to couples who have been unsuccessfully treated by IVF," Troude and her colleagues wrote in their report, published in the journal Fertility and Sterility.

Researchers have previously reported that couples waiting for IVF treatment will occasionally drop off of the wait list because they become pregnant without fertility treatment -- what doctors refer to as a "spontaneous" pregnancy.

To get a better sense of how frequently people going through IVF end up having babies without extra help, Troude and her colleagues collected information on about 2,100 couples who had begun fertility treatment in France in the early 2000s.

About 1,300 of those couples successfully ended up having a baby through IVF.

Eight to 10 years later, the couples responded to a survey about whether they'd had a child on their own following fertility treatment.

Among the parents who'd had a baby through IVF, 17 percent later had another child without assistance. And among couples who originally failed to have a baby with fertility treatment, 24 percent went on to have one from a spontaneous pregnancy.

"It must be borne in mind that infertility did not mean no chance to conceive but low or very low chance to conceive," Troude said.

Dr. Johannes Evers, a professor of obstetrics and gynecology at Maastricht University Medical Center in the Netherlands, said that couples' behavior can explain why people whose IVF didn't work out had a higher rate of natural pregnancies afterward.

"Successful couples already had their child(ren), so they will have used contraception," Evers, who was not involved in the study, wrote in an email to Reuters Health. Men and women who were younger had a better chance of having a baby naturally, as did couples whose infertility didn't have a clear cause.

For instance, among women younger than 35 with unexplained infertility, 45 percent became pregnant after failing to have a baby through IVF.

Infertility can be caused by hormonal problems or low sperm count, for example, but in 12 to 13 percent of couples in the study, the cause was unknown.

Troude said unexplained infertility could be a good sign for couples' chances of having a baby, compared to those who have a clear reason for not initially getting pregnant.

Evers said the findings "reassure (couples) that it is not the end not to conceive by IVF, especially not if they have unexplained infertility."

Another recent study found that among couples who hadn't been able to get pregnant after a year or more of trying, 44 percent of those who opted against fertility treatment still ended up having a baby eventually (see Reuters Health story of February 2, 2012).

Still, it would be difficult to use the new findings to determine which couples might benefit from a wait-and-see approach, and which couples should proceed with IVF, Troude said.

IVF runs for about $15,000 a cycle, and may or may not be covered by insurance.

Troude added that the decision is made all the more challenging given that as a woman ages, her chances of conceiving decline.

Although the findings offer some hope for couples trying to have a baby, she said the long follow-up time in the study and relatively low pregnancy rates "correspond to a very low conception probability."

Evers said the numbers might also overestimate the true birth rate.

That's because only a little more than half of the couples who were invited to participate in the study actually answered the questionnaire, and "pregnant couples will have been more likely to answer than disappointed, childless couples," Evers said.

SOURCE: bit.ly/JPOYTY Fertility and Sterility, online April 21, 2012.

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