A 28-year-old primigravida at 32 weeks gestation presents for routine antenatal care. Symphysis–fundal height is 28 cm (2 cm below expected). Ultrasound confirms estimated fetal weight at 5th percentile for gestational age with normal amniotic fluid volume and normal umbilical artery Doppler. Maternal blood pressure is 118/76 mmHg, urinalysis is normal. What is the most appropriate next step in management?