Fertility starts to decline for women from about the age of 30, dropping down more steeply from the age of 35. As women grow older the likelihood of getting pregnant (with or with out treatment) falls while the likelihood of subfertility rises.
Most women will be able to conceive naturally and give birth to a healthy baby if they get pregnant at 35. After 35 the proportion of women who experience subfertility, risk of miscarriage also tend to increase with the age. By the age of 40 only two in five of those who wish to have a baby will be able to do so.Fertility also declines in men with age, but does very gradually.So men tend to remain fertile for a much longer time compared to women.