This study was done with three major purposes. The first objective was to identify pregnancies associated with the use of the contraceptive implants Implanon and Nexplanon in the UK during two 5-year reporting periods. The second objective was to classify the possible reasons for device failure in cases reported for each implant. The third objective was to examine any differences between reasons for pregnancies associated with these products.

After the initial screening and exclusion of non-relevant studies, 229 Implanon and 234 Nexplanon cases contained sufficient information for analysis. True method failures accounted for a majority of the pregnancies in those using contraceptive implants; the next most common cause was missing implants. In all categories of cases, there was no difference in the frequency of pregnancy observed in the comparison.

The study concluded through its findings that there is still potential for greater avoidance of pregnancies associated with etonogestrel implant use. There is a need for taking a full drug history, timing the insertion on days 1–5 or according to recommended quick starting routines, and palpating the arm after implant insertion.