A 32-year-old pregnant woman at 30 weeks' gestation presents with new-onset hypertension (BP 154/98 mm Hg) and proteinuria (urine protein:creatinine ratio 0.5). She has mild headaches but no visual changes or epigastric pain. Platelets are normal and liver enzymes mildly elevated. According to SOGC Guideline No. 426, what is the most accurate diagnosis?