A 31-year-old cisgender woman with HIV has been taking efavirenz-tenofovir DF-emtricitabine for 6 years. Her last menstrual period was approximately 4 months ago, and she now has a positive pregnancy test. You prescribe a prenatal vitamin and urgently refer her to an obstetrician for prenatal consultation. She is currently tolerating the antiretroviral medications well; recent laboratory studies show a CD4 count of 780 cells/mm³, and an HIV RNA level has consistently been below the limit of detection on this antiretroviral regimen. The obstetrician estimates that she is at 16 to 18 weeks of gestation.