Purpose: The purpose of this study is to evaluate the menstrual profile in users of the etonogestrel (ENG)-releasing implant (Nexplanon) and the possible correlation with anthropometric variables. Methods: Ninety-two healthy women, desiring long-term contraception with the ENG implant were enrolled in a prospective observational study. Anthropometric variables were measured at baseline and after 3, 6, 9, and 12 months. Patients recorded daily the occurrence of any bleeding or spotting. The bleeding/spotting pattern was evaluated over consecutive 90-day intervals (‘‘Reference Periods’’ – RPs). Patients who showed a favourable bleeding profile (amenorrhoea, infrequent, or normal bleeding) for 50% or more of the RPs were assigned to group A, while patients with a favourable bleeding profile for less than 50% of the RPs were assigned to group B. Results: Sixty-eight women (79%) were assigned to group A; 18 (21%) to group B. Group B had a lower baseline body mass index (BMI) than group A (24.84 ± 4.95 kg/m2 versus 20.75 ± 4.41 kg/m2; p50.005). Conclusions: The ENG sub-dermal implant is a well-tolerated contraceptive method, with a high proportion of women experiencing a favourable bleeding profile. The lower basal BMI in Group B in comparison with Group A may account for the higher percentage of irregular bleeding.