The fertility potential of women starts declining at age 40, and therefore the success rates of IVF with own eggs are substantially lower at this point. In short, the chances for success depend on egg quality, but also on egg quantity.
This is the reason why most clinics around the world have an upper age limit for IVF patients using their own eggs. In general, such limit is set between the ages of 43 and 45.
In this sense, IVF with donor eggs may be a good option, as younger women produce high quality eggs, with a lower rate of chromosomal abnormalities to be present. By age 40, 60% of the eggs produced are abnormal.