From about the age of 40 onwards the ovaries gradually cease to function. The supply of follicles in the ovaries decreases. Follicles do not always become fully mature in each cycle. Therefore ovulation does not occur in every cycle. At the same time production of the sex hormones estrogen and progesterone decreases continuously.

The practical consequence of these changes is that periods become irregular. This is a sign of the age-related decline in fertility.

The last menstrual period (menopause) occurs at about the age of 52. This marks the end of the years of sexual maturity. Once she has had her very last period a woman can no longer become pregnant.

But until this is the case she must still use some form of contraception.

However, the decrease in fertility is not the only feature of menopause. The hormonal changes can also lead to menopausal symptoms and contribute to the development of certain diseases.