Women expect their menstrual periods to occur regularly every month, and become concerned when this does not happen. The obvious causes for periods to stop are pregnancy and menopause, and every woman between 15 and 50 who misses a period should be considered pregnant until proved otherwise. Breastfeeding will delay the return of regular menstrual periods. There are also a number of medical conditions that may be responsible for amenorrhoea (a lack of menstrual periods) or oligomenorrhoea (infrequent menstruation).
Any significant emotional trauma (eg. loss of job, death in family), physical stress (eg. vigorous athletic training), serious illness (eg. major infection) or poor nutrition (eg. lack of food, vomiting and diarrhoea) can affect the menstrual cycle. This is a very common phenomenon.
The oral contraceptive pill may cause menstrual periods to become lighter and lighter until they disappear completely. Some women take the pill constantly, without a monthly break off the pill or taking sugar tablets, and stop their periods for the sake of convenience. This practice is completely safe and causes no long-term harm.
Uncommon causes include tumours, cysts or cancer in an ovary that affect the regular cyclical production of oestrogen, a lack of thyroxine (hypothyroidism), Asherman syndrome, Addison’s disease and the Stein-Leventhal syndrome.