There are many reasons why a woman’s ovaries might respond poorly to stimulating fertility drugs. These include a premature menopause. I’ll try to explain this by saying that if you were destined to have your menopause at the age of 41 rather than the average 51 years, then at the age of 36 you would have the average response of a woman of 46. A premature menopause can occur as the result of ovarian surgery or immune disease, or it may simply be genetic if your mother, grandmother and aunts had an early menopause. One sign of a premature menopause is a high FSH hormone level.
Women with PCOS usually respond very well (sometimes too well) to the drugs given to stimulate multiple egg development in IVF cycles, but in a small number of cases the ovaries respond very poorly. This is more common in older women or after pieces of ovary have been removed at surgery or in women who are about to undergo a premature menopause, but often there does not seem to be any reason for such a poor response.
Sadly, however, most cases of poor ovarian response appear to be for no apparent reason, and there is very little that can be done to improve the response. If we had more women who would donate their oocytes (eggs), then we could at least offer oocyte donation, although this would certainly not be what all couples would want.