Administration of norethisterone (0.35 mg/day, as a progestogen only pill) was studied in a group of 16 HIV+ women receiving atazanavir, atazanavir/ritonavir, darunavir/ritonavir or lopinavir/ritonavir. Norethisterone exposure increased by 50% when compared to HIV+ women (n=17) receiving norethisterone without a protease inhibitor.
Effect of protease inhibitors on steady-state pharmacokinetics of oral norethindrone contraception in HIV-infected women. Atrio J, Stanczyk FZ, Neely M, et al. J Acquir Immune Defic Syndr, 2014, 65(1):72-7.

Cervical mucus scores were determined in HIV+ women receiving protease inhibitors (atazanavir, atazanavir/ritonavir, darunavir/ritonavir or lopinavir/ritonavir; n=16) or no protease inhibitors (n=17) before and after taking norethisterone (0.35 mg/day, as a progestogen only pill). Cervical mucus scores were similar at baseline in the two groups and after 21 days of norethisterone. This may suggest no difference in contraceptive efficacy of progestogen only pills in HIV+ women taking a protease inhibitor.
The effect of protease inhibitors on the cervical mucus of HIV-positive women taking norethindrone contraception. Atrio J, Stek A, Vora H, et al. Eur J Contracept Reprod Health Care, 2015, 20(2):149-53.