The average age of menopause (Menopause = No bleeding for 12 months) is 51 years old.
PERI-menopause is the time leading up to and around menopause. It can be up to 10 years long. Nature takes its time to wind down our fertility, just like it takes some time to wind it up in adolescence and early adulthood.
Charting can really help to see where there may be changes in your cycle as you approach this time of your life. You may also notice hot flushes, changes in your period flow. As we get older the luteal phase and length of cycle can become more irregular, you may have earlier ovulation or cycles where you may not ovulate and progesterone levels can decrease.
When trying to conceive later in life and particularly in your 40s (like me) it is good to bear this in mind and keep yourself healthy and seek help as early as possible to maintain optimum hormone levels and egg health.