A 24-year-old primigravida from rural Maharashtra presents to the antenatal clinic for her first ultrasound at what she reports as 20 weeks of gestation based on last menstrual period. On transabdominal ultrasound, the biparietal diameter (BPD) measures 42 mm, femur length (FL) is 28 mm, and head circumference (HC) is 156 mm. Additionally, the sonographer notes absence of the nasal bone on sagittal view. The amniotic fluid volume is normal. What is the most appropriate next step in management?