as you age, problems with your general health affect the reproductive capacity. For ex, if you come from a family of diabetes, you will begin to show early signs of Insulin resistance which affects ovulation. So, even if your ovaries are perfectly fine, their performance gets affected by other health factors. I know I resumed normal ovulation ( PMS, good CM, mittlesmerz... the works)after I started on Metformin to correct the IR imbalance. I will turn 46 soon and can't really complain about my periods, they are like clockwork.