Fetal biometry refers to the set of standardized measurements taken during obstetric ultrasound to assess fetal size and growth. The four core measurements are biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL). These are entered into a formula to calculate estimated fetal weight (EFW). Serial biometry performed 2–4 weeks apart allows assessment of interval growth and detection of intrauterine growth restriction (IUGR) or macrosomia.