Menstrual changes associated with progestogen-only contraception.

Unpredictable disturbance of the menstrual cycle is the major problem associated with use of all progestogen-only methods of contraception. This even occurs with those methods which do not usually suppress ovulation, but the disturbance is generally less severe with lower dosage systems. The commonest changes include amenorrhoea and irregular, scanty and infrequent bleeding, but may sometimes involve episodes of prolonged or frequent spotting or light bleeding. Heavy bleeding is rare. Although some abnormalities of endometrial vascular morphology and function have been identified, the mechanisms of abnormal bleeding are poorly understood. Management centres around effective pretreatment counselling and continued support at follow-up. Sometimes a single course of oestrogen therapy may be helpful. This is safe and effective at stopping a particular episode of bleeding provided that an adequate duration of oestrogen effect is given (eg. an oral 2 to 3 week course or a single intramuscular injection). However, experienced investigators rarely use oestrogens and repeated courses are not recommended. There is clearly a major need for basic research in this area, and for the development of improved systems to minimise the problem.