Maths sheds light on what a delay in getting pregnant means for a couple’s prospects of having a baby

A new mathematical method can help to predict a couple's chances of becoming pregnant, according to how long they have been trying. The model may also shed light on how long they should wait before seeking medical help. For example, the researchers have found that, if the woman is aged 35, after just six months of trying, her chance of getting pregnant in the next cycle is then less than 10 per cent. The analysis, developed at Warwick Medical School at the University of Warwick and the London School of Economics, uses the number of menstrual cycles over which the couple has been trying for a baby to determine a probability of conception within the next month. The method makes use of an important mathematical result first described by Thomas Bayes, an 18th century Presbyterian minister, which allows probabilities to be calculated by combining prior information with new evidence. Peter Sozou of the London School of Economics said: "After several cycles without pregnancy, it becomes relatively more likely that a couple have low fertility. This is the main reason why it becomes less likely that conception will occur in the next cycle".