For couples trying to have a baby, a new mathematical formula devised by scientists may help predict a woman's chance of getting pregnant -- with the model aiming to help clear the murky air over how long a couple should wait before seeking medical help.
Researchers from the Warwick Medical School at the University of Warwick and the London School of Economics have found that if a woman is aged 35, after just six months of trying her chance of getting pregnant in the next cycle is then less than 10 percent. The average 25-year-old woman who has been trying for six months has a 15 percent chance of conceiving in the next month. The average 40-year-old who has been trying for six months has a five percent chance of getting pregnant in the next month.
The analysis uses the number of menstrual cycles over which a couple has been trying for a baby to determine a probability of conception within the next month.
"After several cycles without pregnancy, it becomes relatively more likely that a couple have low fertility," says Dr. Peter Sozou of the London School of Economics. "This is the main reason why it becomes less likely that conception will occur in the next cycle."
"Many couples are not aware that chance plays a big role in getting pregnant," adds Dr. Geraldine Hartshorne of Warwick Medical School. "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."
"We can't work out exactly when, or if, a woman will become pregnant," adds Hartshorne. "But this analysis can predict her chances, and give a percentage estimate of pregnancy in the next cycle."
The standard rule of thumb is that couples trying to conceive should wait a year before seeking help, while older couples should wait around three to six months.
The research was published Thursday in the open access journal PLOS ONE.