Your periods may change significantly while using a contraceptive implant. Around 20% of women using the implant will have no bleeding, and almost 50% will have infrequent or prolonged bleeding. Bleeding patterns are likely to remain irregular, although they may settle down after the first year. Although these changes are not harmful, they may not be acceptable for some women. Other side effects that some women report are: headaches, acne, nausea, breast tenderness, changes in mood, loss of sex drive.