Vaginal bleeding patterns in women using once-a-month injectable contraceptives.Contraception. 1994 Apr; 49(4):399-420.C
The main raison d'être for the development of once-a-month injectable contraceptives is the need for a long-acting method which produces a regular vaginal bleeding pattern. Although many women will successfully tolerate the amenorrhea or irregular bleeding which frequently accompany use of long-acting progestogen-only methods, there is a substantial minority, especially in certain ethnic groups, who find this unacceptable. The extensive literature does indicate that although combined estrogen-progestogen once-a-month injectables produce much more regular bleeding patterns than long-acting injectables like depot-medroxyprogesterone acetate, the patterns are not entirely normal. Detailed studies by the World Health Organization have demonstrated some deviation from normal menstrual patterns by users of the two once-a-month injectables, Cyclofem and Mesigyna. For example, 23.5% of Cyclofem and 25.2% of Mesigyna users experience irregular bleeding between 3 and 6 months of use compared with 4.8% of untreated women, and 13.3% of Cyclofem and 11.1% of Mesigyna users experience prolonged bleeding compared with 2.3% of untreated women. Comparable figures are much worse for DMPA users with a 35.7% incidence of irregular and 27.7% incidence of prolonged bleeding after similar duration of use. Bleeding patterns with all long-acting methods tend to improve with time. Overall group data for once-a-month injectable users are reasonably close to those of untreated women with, for example, a median of 15.6 days (5th and 95th percentiles: 7.5 and 26; confidence limits) of bleeding or spotting per 90-day reference period compared with a median of 18.5 days (5th and 95th percentiles: 12.2 and 25.5) for untreated women. Twelve-month life table discontinuation rates for menstrual bleeding disturbances are lower than expected for most progestogen-only methods at 2.1-5.2% for Cyclofem and 0.8-4.2% for Mesigyna for amenorrhea, and 6.3-12.7% for Cyclofem and 7.5-12.0% for Mesigyna for bleeding-related reasons. Once-a-month injectable contraceptives produce vaginal bleeding patterns much closer to normal than other injectables, but there are still significant deviations which lead to some discontinuation for menstrual reasons. Hence, full explanation and counselling about possible menstrual changes are still essential for all intending users of these methods.