Fertility declines with age because fewer eggs remain in your ovaries, and the quality of the eggs remaining is lower than when you were younger. Blood tests are now available to determine your ovarian reserve, a term which reflects your age-related fertility potential.
In the simplest of these tests, the hormones follicle-stimulating hormone (FSH) and estradiol are tested in your blood on the second, third, or fourth day of your menstrual period.
An elevated FSH level indicates that your chances for pregnancy may be lower than routinely expected for your age, especially if you are age 35 or older. Abnormally high FSH levels do not mean that you have no chance of successful conception.
However, they may indicate that success rates may be lower, that more aggressive treatment may be warranted, and/or that higher medication doses may be needed.
Older women tend to have a lower response to fertility medications and a higher miscarriage rate than younger women. The chance of having a chromosomally abnormal embryo, such as one with Down syndrome, also increases with age.
Because of the marked effect of age on pregnancy and birth rates, it is common for older couples to begin fertility treatment sooner and, in some cases, to consider more aggressive treatment than younger couples.