The progestogen-only pill (POP), minipill, is quite an effective second line contraceptive. Despite this, it is used relatively infrequently except during lactation. The main reason for this is that women on POP often have abnormal bleeding patterns, with an increased frequency of bleeding, lengthened cycles, breakthrough bleeding, spotting and prolonged bleeding. These menstrual disturbances are the most common quoted reason for discontinuation in up to 25% of users.
PIP: Although the progestogen-only minipill decreases side effects such as dizziness, nausea, headaches, and breast tenderness associated with combined oral contraceptives, this advantage is outweighed by disturbances of menstrual flow. 1/3 - 1/2 of minipill users experience prolonged menstruation, and up to 70% report breakthrough bleeding or spotting in 1 or more cycles. These menstruation disorders are the most frequently cited reason for method discontinuation. In some studies, under 50% of mini-pill users continued method use for 12 months. Morphometric studies of endometrial biopsies from progestogen-only pill users suggest that the endometrial response is variable and unpredictable, including irregular secretory endometrium and a lack of or suppressed proliferation. Other studies have found increases in the total and dilated veins at the endometrial-myometrial junction in minipill users. New strategies to improve cycle control would enhance acceptance of this excellent second line contraceptive method.