A 36-year-old G1P0 woman at 32 weeks' gestation presents with a 1-week history of worsening generalised oedema, headaches and visual blurring. Blood pressure is 168/110 mmHg on two readings 4 hours apart. Urinalysis shows 3+ protein. Reflexes are brisk with 1 beat of clonus. What is the most appropriate immediate management?