THURSDAY, Oct. 4, 2012 (HealthDay News) -- Researchers who developed a mathematical model to help predict a couple's chances of becoming pregnant say the method may help determine how long couples should wait before seeking medical help to achieve pregnancy.
The method determines the probability of conception within the next month by using the number of menstrual cycles that have occurred during the time a couple has been trying to conceive.
For example, the U.K. researchers found that a 35-year-old woman who has been trying for six months to get pregnant has only a 10 percent chance of conceiving within the next month.
In comparison, the number of months required to reach a conception chance below 10 percent is 10 months at age 30 and 13 months at age 25, according to the study appearing online Oct. 4 in the journal PLoS One.
"Many couples are not aware that chance plays a big role in getting pregnant. People expect to get pregnant when they want to, so finding out that it isn't happening can be a shock. Approaching a doctor about such a personal matter is daunting, so knowing when is the right time to start investigations would be a useful step forward," study author Geraldine Hartshorne of Warwick Medical School, said in a University of Warwick news release.
"We can't work out exactly when, or if, a woman will become pregnant -- but this analysis can predict her chances, and give a percentage estimate of pregnancy in the next cycle," she added.
Common wisdom has been that couples who are trying to get pregnant should have regular sex for a year before seeking help, but this study shows that age also affects this decision.
"Comparatively few young couples have low fertility, and so for these couples, the most likely reason for failing to conceive in the first few cycles is simply bad luck. There is quite a good chance of conception if they keep trying," study author Peter Sozou, of the London School of Economics, said in the news release.
"But older couples are more likely to have low fertility, so it's more likely for them than for younger couples that failure to conceive after a few months is due to low fertility," he noted.
The U.S. National Institute of Child Health and Human Development has more about infertility/fertility.