The menopause is when a woman stops having periods and is no longer able to get pregnant naturally. Periods usually start to become less frequent over a few months or years before they stop altogether. Sometimes they can stop suddenly. The menopause is a natural part of ageing that usually occurs between 45 and 55 years of age, as a woman’s oestrogen levels decline. In the UK, the average age for a woman to reach the menopause is 51. However, around 1 in 100 women experience the menopause before 40 years of age. This is known as premature menopause or premature ovarian insufficiency.