Most Implanon users experience a reduction in the frequency and volume of menstrual bleeding, but a substantial minority experience unpredictable and frequent and/or prolonged episodes of bleeding. This is a double blind, placebo controlled, randomised study with an additional randomised non-blinded arm. Two hundred women between the ages of 18-45 years, who are Implanon users with prolonged or frequent breakthrough bleeding (WHO definition) will be recruited and randomised into 4 equal-sized treatment groups of 50 women assigned to Marvelon 7 days or 21 days, NuvaRing 21 days or placebo. Recruited subjects will maintain a daily menstrual diary chart for a minimum of 90 days prior to randomisation, and will be enrolled into the treatment phase provided that they have met one of the World Health Organization criteria for prolonged or frequent bleeding Following the initial 90 day record, eligible women will begin designated treatment on day 1 of the next episode of bleeding or spotting. Analysis of the subsequent menstrual pattern will begin from day 1 of that bleeding/spotting episode and will continue through 90 days.