We explored the potential causes associated with pregnancies occurring in patients using an etonogestrel contraceptive implant (Implanon). Three cases of treatment failure were reported where no predisposing factors were found (i.e. Body Mass Index, hepatic inducing therapy). Etonogestrel plasmatic detection was positive in two cases whereas in the third case with negative endocrinological makers, neither palpation nor ultrasonography identified the device. Therefore, true contraceptive failure can be considered in two of the reported cases. Furthermore, pregnancies associated with Implanon use warrant additional attention including notification to drug monitoring centers and Organon SA.
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