What are the disadvantages of DMPA as a method of contraception? DMPA changes bleeding/period patterns. These changes are a result of the hormonal effect to the lining of the uterus. It is not possible to predict which changes will occur, but they can include: During the first months of use, episodes of irregular bleeding and spotting lasting seven days or longer are common. The frequency and duration of such bleeding decrease with increasing duration of use. After one year of use, 50 percent of women have no periods and with ongoing use, this rate of amenorrhea (no periods) increases to 70 percent. Or irregular bleeding or spotting Sometimes, prolonged bleeding (this is usually light, but can be inconvenient for some women) Heavy bleeding (rare) Fertility - possible delay in return to fertility; on average, the delay is about 9 months from the last DMPA injection. Return of fertility may be delayed after discontinuing DMPA. the average time to return to a previous menstrual pattern is 8 months after last DMPA. Within 12 months 78 percent of women who are trying to conceive will become pregnant. In a small proportion of women, fertility is not reestablished until 18 months after the last injection.