The etonogestrel (ENG) implant is the most effective contraceptive method available. However, its use is complicated in high-HIV prevalence settings because data show reduced implant efficacy during efavirenz-based (EFZ) ART therapy. New, more effective strategies for concomitant ART/implant use need to be identified. Dolutegravir-based (DTG) ART, first-line ART in many resource-rich countries, is now being introduced in Africa. This study will evaluate whether DTG/implant combination avoids drug-drug interactions that lead to unintended pregnancies and reduced contraceptive efficacy with EFZ. The proposed parallel-group study will take place in Gabarone, Botswana to compare steady state plasma concentrations of ENG in Botswanan implant-users with HIV in three groups; those receiving EFZ-based ART, DTG-based ART, and ART-naive women. A secondary aim will be to describe what proportion of women in each group have plasma ENG concentration levels below that needed for ovulation suppression; thus indicating compromised contraceptive efficacy. This question is of clinical importance for the whole of Africa as DTG use is expanded, and the answer will enable the development of evidence-based guidance to optimize contraceptive care for HIV-infected women.