Fertility is defined as the capacity to produce children. As women get older, their fertility decreases. Once a woman passes 30, her fertility decreases significantly each year. Within individuals, the chance of getting pregnant remains relatively stable from cycle to cycle. However, the chance of getting pregnant is highest in the first months of unprotected intercourse and declines gradually thereafter in the population as a whole. If no conception occurs within 3 months, monthly fecundability (the probability of pregnancy per month) decreases substantially among those who continue their efforts to conceive.
Fertility varies among populations and declines with age in both men and women, but the effects of age are much more pronounced in women. Relative fertility is decreased by about half among women in their late 30s compared with women in their early 20s. For women over age 35 years, an infertility workup is recommended after 6 months of trying to get pregnant unsuccessfully or if there are known issues.
Although semen parameters in men also decline detectably after 35 years of age, male fertility does not appear to decrease appreciably before approximately age 50.