A pregnant client at 10 weeks is found to have HIV. Which medication is most important to initiate immediately?

HIV IN PREGNANCY — NURSING PRIORITY: INITIATE ART IMMEDIATELY: All pregnant women with HIV should start antiretroviral therapy regardless of CD4 count; the primary goal is viral suppression to undetectable levels (<20-40 copies/mL) by delivery; PERINATAL TRANSMISSION: Without ART, transmission risk is 15-45%; with ART achieving undetectable viral load: <1%; REGIMEN SELECTION: Three-drug ART combination; avoid efavirenz in first trimester (neural tube defect risk); preferred regimens include dolutegravir-based (with folic acid supplementation); INFANT PROPHYLAXIS: Newborn receives ART prophylaxis (usually zidovudine/AZT for 4-6 weeks); breastfeeding: not recommended in resource-rich settings (formula substitution eliminates breastfeeding transmission risk); DELIVERY: If viral load >1,000 copies/mL near delivery, caesarean section recommended to reduce transmission; monitoring: viral load at 36 weeks to guide delivery decision.