CNS Pharmacology USMLE Step 1 Practice Question

A 29-year-old pregnant woman at 24 weeks gestation presents to her obstetric clinic for a routine prenatal visit, during which persistent hypertension is noted on two separate readings (BP 152/98 mmHg and 154/96 mmHg, HR 88, RR 16, temperature 98.6°F). She reports no headaches, visual changes, epigastric pain, or swelling of the hands and face. Physical examination reveals mild bilateral lower extremity pitting edema, a gravid uterus consistent with gestational age, and no papilledema on fundoscopic examination. Urinalysis shows no proteinuria, serum creatinine is 0.9 mg/dL, and liver enzymes are within normal limits. Fetal heart tones are 148 bpm and reassuring. She takes only prenatal vitamins and has no prior history of hypertension before this pregnancy. Which medication lowers blood pressure by stimulating central alpha-2 receptors and is classically considered safe throughout pregnancy?