The odds for pregnancy in women over 35-37 are low. For this reason, AI is not recommended at ages beyond 35.
From age 35 onwards, and especially at 40, a woman's ovarian reserve drops dramatically, while the chances for the eggs to have chromosomal alterations are higher.
The success rate of donor insemination in women younger than 40 is around 20-22%, while it drops to 13% in women aged 40. In the case of artificial insemination with husband's sperm, the percentage is 12-14% before age 40, and 9% in women aged 40 or more.