For healthy couples in their 20s or early 30s, the chance that a woman will get pregnant is about 25 to 30 percent in any single menstrual cycle. This percentage starts to decline in a woman’s early 30s. By age 40, a woman’s chance of getting pregnant drops to less than 10 percent per menstrual cycle. A man’s fertility also declines with age, but not as predictably.
Sometimes problems getting pregnant for a second or subsequent time are related to a complication that occurred in a prior pregnancy or prior to delivery (damage to the uterus, for instance). But most often, secondary infertility is caused by the same factors that would cause primary infertility — issues like advanced age, obesity, ovulation problems and so on.