A 12 months longitudinal study was carried out in 214 consecutive Nigerian women using Nomegestrol acetate subdermal contraceptive implant (Uniplant) for the first time to establish the rates of different vaginal bleeding patterns according to WHO bleeding/spotting classification, and to assess their relationship with Uniplant discontinuation. The results showed an initial rise in the number of women experiencing altered vaginal bleeding which continued to fall towards the 12th month of use (57.01% vs 26.17%). Similarly, a significant increase in mean menstrual cycle length occurred in the first trimester of use and this disappeared by the third trimester. The mean numbers of bleeding/spotting days and bleeding/spotting free intervals increased significantly from first trimester to the fourth trimester. No change was noted in the mean number of bleeding/spotting episodes through, out the follow up period. The total discontinuation rate was 15.42%. Discontinuation on account of altered vaginal bleeding pattern was 3.27%. One accidental pregnancy occurred during follow up (Pearl index = 0.52). No significant change in haemoglobin levels was noted in the women. It was concluded that changes in menstrual patterns in Uniplant users occur mostly in the first six months of use and are unlikely to have any deleterious effects on the general health of the users.