A 32-year-old primigravida at 34 weeks' gestation presents with severe headache, visual disturbances, and right upper quadrant pain. Blood pressure is 172/112 mm Hg on two measurements 15 minutes apart. Reflexes are brisk with 2 beats of clonus. Urinalysis shows 3 plus protein. Platelets are 90 × 10^9/L and ALT is twice the upper limit of normal. What is the most appropriate immediate management step?